GC113 Can We Get Married Pre-marital, Pre-pregnancy And Pre-natal Counselling
Pre-marital, pre-pregnancy, and pre-natal counseling is a comprehensive genetic and medical assessment provided to couples before marriage, conception, or during pregnancy to identify hereditary disorders, optimize maternal-fetal health, and guide informed reproductive decision-making.
Pre-Marital, Pre-Pregnancy and Prenatal Counselling
Lecture Map
This lecture answers one deceptively simple question a couple may bring to any doctor: "Can we get married and should we have children?" The answer requires a systematic framework to identify reproductive risks (both maternal and fetal), mitigate them before or during pregnancy, and guide couples through the complex landscape of screening, diagnosis, and decision-making. The lecture spans the continuum from pre-marital health checks through pre-pregnancy optimization to antenatal screening and prenatal diagnosis.
- Understand reproductive risks — maternal and fetal
- Know how to identify risks (history, examination, screening tests)
- Understand options for at-risk couples
- Appreciate counselling concerns (ethics, communication, support)
Why Pre-Pregnancy Counselling Matters — First Principles
The objective of pre-marital and pre-pregnancy counselling is to detect and assess any specific health problems in the woman or her partner that may be relevant and managed prior to pregnancy, AND to obtain general advice about optimizing personal health care and lifestyle. [1]
Why this matters from first principles: Many congenital anomalies occur in the first 4–8 weeks after conception — often before a woman even knows she is pregnant. Neural tube closure happens by day 28. Organogenesis is largely complete by week 12. If you wait until the booking visit to address teratogens, folate deficiency, or uncontrolled medical conditions, the window of prevention has already closed. This is why counselling should occur before conception.
Pre-pregnancy counselling is appropriate whether the reproductive-aged patient is currently using contraception or planning pregnancy. As health status and risk factors can change over time, pre-pregnancy counselling should occur several times during a woman's reproductive lifespan. [1]
Why repeated counselling? A 25-year-old with no medical history may develop diabetes, hypertension, or an autoimmune condition by age 32. Her medication list changes. New family history may emerge (e.g., a sibling's child born with a genetic condition). Each pregnancy also carries new risks (e.g., prior preeclampsia, gestational diabetes).
Reproductive Risks
Maternal reproductive risks include: pre-existing medical conditions, pregnancy-related complications, operative risk, and psychosocial problems. [1]
| Category | Examples | Why It Matters |
|---|---|---|
| Pre-existing medical conditions | DM, HTN, epilepsy, SLE, thyroid disease, cardiac disease, renal disease | Uncontrolled disease → worse maternal & fetal outcomes; some medications are teratogenic |
| Pregnancy-related complications | Preeclampsia, GDM, placenta praevia, APH, PPH | Prior Hx increases recurrence risk |
| Operative risk | Previous C-section, uterine surgery | Scar dehiscence/rupture risk in subsequent pregnancies |
| Psychosocial problems | Depression, IPV, substance use, lack of social support | Affects antenatal care compliance, maternal-fetal bonding, postnatal outcomes |
Fetal reproductive risks include: growth problems, congenital anomalies, infection, and birth trauma. [1]
Congenital anomalies can be: chromosomal/genetic, structural, or functional. [1]
| Category | Examples | Detection Method |
|---|---|---|
| Growth problems | IUGR, macrosomia | Serial USG, SFH measurement |
| Congenital anomalies — Chromosomal | Trisomy 21 (Down syndrome), Trisomy 18, Trisomy 13, Turner syndrome | Screening tests → invasive diagnosis |
| Congenital anomalies — Genetic | Thalassaemia, cystic fibrosis, SMA | Carrier screening → prenatal DNA analysis |
| Congenital anomalies — Structural | NTD, congenital heart defects, renal anomalies | Morphology scan 18–22 weeks |
| Congenital anomalies — Functional | Congenital hypothyroidism | Neonatal screening (not prenatal) |
| Infection | Rubella, CMV, toxoplasmosis, syphilis, HBV, HIV | Routine booking tests for specified infections/immunity plus pathogen- and exposure-directed testing; a blanket “TORCH screen” is not a universal test |
| Birth trauma | Shoulder dystocia, brachial plexus injury | Risk assessment → delivery planning |
The growth table on slide 8 links early-onset maternal hypertension with fetal growth restriction and suboptimally controlled gestational diabetes with macrosomia. It also reminds the reader not to assume every growth problem is maternal: fetal syndromes and infection can cause growth restriction, while some syndromes cause overgrowth.
Risk Identification: The Clinical Approach
1. History Taking [1]
This is the backbone of pre-pregnancy counselling. The lecture systematically covers:
Age is a key risk factor. [1]
- Why: Advanced maternal age ( ≥ 35 at delivery) increases risk of chromosomal aneuploidies (especially Trisomy 21), miscarriage, GDM, preeclampsia, placenta praevia, C-section. Paternal age > 40 also increases risk of new autosomal dominant mutations.
- Why: Certain genetic conditions cluster in specific ethnic groups. For HK Chinese, the most important is thalassaemia (α-thal and β-thal). In HK Chinese with low MCV: ~5% are α-thal carriers, ~3% are β-thal carriers, ~0.3% have HbE. Overall ~11.3% carry a thalassaemia allele. [3]
- Why: Consanguineous couples share more DNA identical by descent, increasing the chance that both carry the same rare recessive variant. For offspring of first cousins, the inbreeding coefficient is 1/16 (6.25%): at a given autosomal locus, this is the probability that the two alleles are identical by descent, not a 6.25% risk of a recessive disease.
If high risk of a chromosomal or genetic disorder based on family history, referral to pre-pregnancy genetic counselling is preferred to allow more reproductive options. [1]
Why pre-pregnancy referral is preferred: Before conception, the couple has the widest range of options: natural conception with prenatal diagnosis, preimplantation genetic testing (PGT) with IVF, use of donor gametes, adoption, or choosing not to have biological children. Once pregnant, options narrow to prenatal screening/diagnosis and decisions about continuation vs. termination.
The lecture's pedigree diagrams are best read as visual patterns:
| Inheritance Pattern | Key Features | Examples |
|---|---|---|
| Autosomal dominant | A vertical pattern through successive generations; both sexes affected; father-to-son transmission is possible. A heterozygous affected parent usually gives each child a 50% chance of inheriting the variant. | Huntington's, Marfan syndrome, achondroplasia |
| Autosomal recessive | A horizontal cluster of affected siblings with clinically unaffected parents; consanguinity may be visible. If both parents carry the same variant, each pregnancy has 25% affected, 50% carrier and 25% unaffected/non-carrier probabilities. | Thalassaemia, CF, SMA, PKU |
| X-linked | No father-to-son transmission. Affected males may be connected through carrier females; heterozygous females can still manifest disease because of X-inactivation. | Haemophilia, Duchenne MD, G6PD deficiency |
Pedigree appearance suggests a mode of inheritance but does not prove it: small families, de novo variants, reduced penetrance and variable expression can obscure the textbook pattern.
Discussion on how the medical condition may affect, or be affected by, a pregnancy. Stabilisation of pre-existing medical condition. Multidisciplinary pre-pregnancy planning. [1]
Key examples for exam:
| Condition | Effect on Pregnancy | Effect of Pregnancy on Condition | Pre-pregnancy Action |
|---|---|---|---|
| Epilepsy | Some antiseizure medicines carry fetal malformation and neurodevelopmental risks | Seizure frequency and drug levels may change | Arrange specialist review before conception; use the most appropriate effective regimen and prescribed folic acid. Do not stop or switch treatment abruptly. [16] |
| Diabetes | ↑ congenital anomalies (NTD, cardiac), macrosomia, stillbirth | Insulin requirements change each trimester | Optimize glycaemia before conception without problematic hypoglycaemia and review glucose-lowering medicines with the diabetes-obstetric team |
| Hypertension | Superimposed preeclampsia, fetal growth restriction, placental abruption | BP may initially fall then rise | Review ACE inhibitors/ARBs and plan an appropriate alternative before conception where possible; maintain adequate BP control |
| SLE | Flare, preeclampsia, fetal growth restriction, neonatal lupus (anti-Ro → congenital heart block) | Flares can occur, especially postpartum | Aim for quiescent disease, assess renal/antibody risk, continue pregnancy-compatible disease control and replace teratogenic medicines under specialist supervision |
| Thyroid disease | Graves' → fetal/neonatal thyrotoxicosis; uncontrolled hypothyroidism → adverse neurodevelopmental/obstetric outcomes | hCG and pregnancy alter thyroid physiology and dose requirements | Achieve biochemical control and agree a trimester-specific antithyroid/levothyroxine monitoring plan; PTU and methimazole/carbimazole have different gestational risks [2] |
Review current medications including over the counter on appropriateness and teratogenic potential. May need adjustment of medication prior to pregnancy to optimize disease control and minimize teratogenic risk. [1]
Medication Safety: Review, Do Not Self-Stop
The slide's instruction is to review all prescribed, over-the-counter and complementary medicines and adjust them when indicated before pregnancy. It is unsafe to turn this into a blanket “stop or switch” list: uncontrolled epilepsy, bipolar disorder, hypertension, autoimmune disease or thrombosis can also endanger parent and fetus.
- Valproate has major congenital-malformation and neurodevelopmental risks and generally requires specialist-led avoidance or a pregnancy-prevention programme; a patient already taking it must not stop abruptly. [16]
- ACE inhibitors/ARBs, methotrexate, isotretinoin and mycophenolate usually require a planned preconception alternative or washout, with timing determined from the indication and product/specialist guidance.
- Warfarin crosses the placenta, but anticoagulation in a mechanical heart valve is a high-risk exception requiring an individualized obstetric-cardiology/haematology plan rather than an automatic switch.
- The FDA removed the class-wide pregnancy contraindication for statins: most pregnant patients can pause treatment, but continuation can be reasonable in selected patients at very high cardiovascular risk. Inadvertent early exposure is not by itself an indication for pregnancy termination. [17]
- Lithium and antidepressants require individualized risk-benefit review; neither should be automatically substituted based on a one-line table.
- Previous uterine surgery → scar integrity concerns
- Drug allergies → important for labour/anaesthesia planning
- Occupation → exposure to radiation, chemicals, infections (healthcare workers, lab staff, teachers)
Smoking, alcohol and substance use should be stopped before conception. No known safe level of alcohol consumption during pregnancy. Considered for both parents when relevant. [1]
- Smoking: ↑ risk of IUGR, preterm labour, placental abruption, SIDS. Nicotine and CO cross the placenta.
- Alcohol: Fetal alcohol spectrum disorder (FASD) — growth restriction, facial features, neurodevelopmental impairment. No safe threshold.
- Substance use: Cocaine → placental abruption, IUGR; Opioids → neonatal abstinence syndrome.
- STI risk, intimate partner violence (IPV): Screen sensitively. IPV often escalates during pregnancy.
Well balanced diet. Weight management. Periconceptional folic acid supplementation. [1]
Folic Acid Supplementation — Key Details
Standard dose: at least 400 micrograms (0.4 mg) daily, ideally starting 3 months before conception and continuing through the first 12 weeks. Hong Kong Family Health Service advises 400 micrograms daily and no more than 1,000 micrograms from routine supplements. [14]
High dose (5 mg daily, prescribed): Consider for a previous NTD-affected pregnancy, personal/partner/family history of an NTD or other congenital malformation, pre-existing type 1 or type 2 diabetes, a haematological condition requiring folate (including thalassaemia), or medicines that interfere with folate absorption/metabolism (including some antiseizure and HIV medicines). Current NICE guidance specifically says BMI ≥25 kg/m² alone is not an indication for more than 400 micrograms. [15]
Why: Folate is essential for DNA synthesis and neural tube closure (completes by day 28 post-conception). Deficiency → neural tube defects (spina bifida, anencephaly).
- Weight management: BMI < 18.5 → anovulation, IUGR; BMI ≥ 30 → GDM, preeclampsia, macrosomia, NTD, increased anaesthetic risk.
Hepatitis B, rubella and varicella immunization can be considered for women with incomplete immunity. Seasonal influenza vaccination in pregnancy is safe. [1]
| Vaccine | Timing | Why |
|---|---|---|
| Rubella (MMR) | Pre-conception (live vaccine → wait ≥ 4 weeks before conceiving) | Congenital rubella syndrome: cataracts, deafness, CHD, IUGR |
| Varicella | Pre-conception (live vaccine) | Congenital varicella syndrome (limb hypoplasia, skin scarring, eye defects) |
| Hepatitis B | Pre-conception or antenatal | Prevent vertical transmission |
| Influenza (inactivated) | Safe at any gestation; recommended seasonally | Pregnant women are at higher risk of severe influenza [18] |
| Pertussis-containing vaccine | During each pregnancy; the current HK programme window is 26–34 weeks | Passive antibody protects the newborn before infant vaccination [19] |
Key rule: Live attenuated vaccines such as MMR and varicella are generally avoided during pregnancy; review vaccine-specific guidance rather than assuming that every non-live product is automatically indicated. Inactivated influenza and the recommended pertussis-containing vaccine are established antenatal examples.
Travel and environmental risks — reduce the chance of infection. [1]
- Zika virus (teratogenic → microcephaly), malaria (severe in pregnancy), traveller's diarrhoea
- Advise postponing travel to endemic areas; chemoprophylaxis for malaria if travel unavoidable
Obstetric history: congenital anomalies, stillbirth, neonatal death, recurrent pregnancy loss, grand multiparity, difficult delivery, birth trauma. [1]
- Prior congenital anomaly → recurrence risk depends on aetiology (chromosomal vs. multifactorial vs. single gene)
- Stillbirth/neonatal death → investigate cause; may indicate genetic condition, placental insufficiency
- Recurrent pregnancy loss: definitions vary. RCOG defines recurrent miscarriage as 3 or more first-trimester miscarriages (not necessarily consecutive) but supports earlier evaluation after 2 when a pathological cause is suspected; ESHRE considers the diagnosis after 2 or more losses. Take the complete loss history and follow the local pathway. [27]
- Grand multiparity ( ≥ 5 deliveries) → higher risk of malpresentation, PPH, placental problems
General examination: auscultation of heart sounds, breast examination, cervical screening, +/- other tests as indicated. Blood pressure, body mass index. [1]
| Component | What You're Looking For |
|---|---|
| BP | Baseline for comparison; chronic HTN if elevated |
| BMI | Underweight or obese → specific risks |
| Heart auscultation | Undiagnosed structural heart disease (especially mitral stenosis — poorly tolerated in pregnancy due to volume overload) |
| Breast examination | Exclude breast pathology before pregnancy/lactation |
| Cervical screening | Check whether screening is due and follow the local cervical-screening pathway; an abnormal result needs appropriate follow-up rather than being ignored because of pregnancy |
3. Screening Tests [1]
Complete blood picture (including Hb, MCV), blood group + Rhesus factor, infection screen (VDRL, Hepatitis B, rubella antibody, HIV antibody), cervical smear, urine protein and sugar. [1]
| Test | Purpose | Key Thresholds |
|---|---|---|
| CBP (Hb, MCV) | Detect anaemia; low MCV triggers assessment for thalassaemia and iron deficiency | Current HK public information uses MCV ≤80 fL as the screen-positive threshold [21] |
| Blood group + Rh | Rh-negative mother at risk of alloimmunization | Anti-D prophylaxis if Rh-negative |
| VDRL | Syphilis screening | If positive → confirmatory FTA-ABS |
| HBsAg | Hepatitis B carrier status | Carrier → vertical transmission risk; neonatal HBIg + vaccination |
| Rubella antibody | Immunity status | Non-immune → vaccinate pre-conception |
| HIV antibody | HIV status (opt-out screening in HK) | If positive → cART to prevent MTCT |
| Cervical smear | Cervical cytology / HPV screening | Per HK guidelines |
| Urine protein/sugar | Baseline renal function, occult DM | Proteinuria → renal disease workup |
Available screening tests for low-risk women for carrier of more common genetic conditions (e.g., thalassaemia). [1]
This is a very high-yield topic for HKUMed exams. The 2023 Fourth Summative MCQ directly tested this. [9]
The HK screening strategy shown by the flowchart:
- Check MCV at booking visit
- If it is low → check the partner's MCV
- If both have low MCV → refer for definitive haemoglobin and/or molecular studies and genetic counselling
There is a threshold discrepancy within the deck: its reproduced 2003 HKCOG algorithm uses MCV < 80 fL, whereas the later α-/β-carrier slides use MCV < 82 fL. Current Family Health Service patient information uses MCV ≤80 fL. In practice, follow the current laboratory/local programme cut-off; the exam-level action is “low maternal MCV → test the partner.” [21]
The lecture then contrasts typical carrier patterns:
| Feature | α-Thalassaemia Carrier | β-Thalassaemia Carrier |
|---|---|---|
| MCV | < 82 fL | < 82 fL |
| HbA (α₂β₂) | Present | Present |
| HbA₂ (α₂δ₂) | Normal | Raised ( > 3.5%) |
| HbF (α₂γ₂) | Normal | May be raised |
| HbH inclusion bodies (β₄) | May be detected and support α-thalassaemia | Negative |
| Iron studies | Normal or raised | Normal or raised |
Diagnosis of α-thalassaemia carrier: HbA₂ normal, HbF normal, HbH granules positive, MCV < 82 fL, Fe normal or raised. [1]
Diagnosis of β-thalassaemia carrier: HbA₂ raised, HbF raised, MCV < 82 fL, Fe normal or raised. [1]
Exam Trap: α-thal vs β-thal Carrier
The key discriminator in the lecture is HbA₂ level: typically normal in α-thalassaemia trait and raised in β-thalassaemia trait. HbH inclusions support α-globin deficiency but are not present in every α-thalassaemia carrier, so a negative preparation does not exclude it. Iron deficiency can coexist with thalassaemia; check ferritin and give iron only when deficiency is demonstrated.
Why iron is important: Low MCV can be from iron deficiency OR thalassaemia. If iron is low, treat iron deficiency first, then recheck MCV. If MCV remains low despite iron repletion → thalassaemia screening.
Understanding the genetics from the lecture diagrams:
- α-globin genes: 4 copies (2 on each chromosome 16). Deletions range from 1 (silent carrier, often normal or near-normal MCV) to 4 (Hb Bart's hydrops fetalis — usually fatal without fetal therapy).
- β-globin genes: 2 copies (1 on each chromosome 11). β⁺ (reduced production) or β⁰ (no production).
The gene-cluster and expression figures add the mechanistic explanation:
- The α-like cluster is on chromosome 16 and the β-like cluster is on chromosome 11.
- Embryonic ζ and ε chains fall rapidly early in gestation. α-chain expression rises by about 6 weeks and remains high before and after birth.
- Fetal haemoglobin is HbF (α₂γ₂). Around birth, γ-chain production falls while β-chain production rises, producing adult HbA (α₂β₂); a small δ-chain contribution forms HbA₂ (α₂δ₂).
- Therefore severe α-thalassaemia presents in fetal life, whereas severe β-globin deficiency is partly masked by HbF and classically becomes evident after the postnatal γ-to-β switch.
| # α-gene deletions | Clinical Phenotype | MCV |
|---|---|---|
| 1 deleted (αα/α-) | Silent carrier | Normal |
| 2 deleted (αα/-- or α-/α-) | α-thal trait | Low |
| 3 deleted (α-/--) | HbH disease | Very low; moderate anaemia |
| 4 deleted (--/--) | Hb Bart's hydrops fetalis | Usually fatal without fetal therapy; severe maternal and fetal morbidity |
For a two-gene deletion, phase matters: cis (--/αα) can combine with a partner's cis deletion to produce Hb Bart's disease, whereas trans (-α/-α) does not create a four-gene-deletion fetus with the same partner genotype. The slide also depicts non-deletional variants, so severity cannot always be inferred from deletion count alone.
The slide presents Hb Bart's hydrops fetalis as “lethal,” reflecting its natural history. This is no longer absolute: specialist intrauterine transfusion can produce viable survivors, but the child generally remains transfusion-dependent and counselling must cover uncertain neurodevelopmental outcome as well as major maternal complications from untreated hydrops. [22]
Expanded carrier screening is currently not funded by the public health system. Cost effectiveness, acceptance and uptake uncertain. Detailed pretest counselling on benefits and limitations of testing required. [1]
This is a panel-based approach testing for hundreds of recessive conditions simultaneously. Important counselling points: may reveal carrier status for conditions with uncertain clinical significance; psychological impact; not 100% detection rate.
Antenatal Screening Tests in Hong Kong [1]
This is the 2024 lecture's examinable schedule. [1]
| Gestation | Test | Purpose |
|---|---|---|
| First booking | Hb, MCV, HBsAg, Rubella Ab, VDRL/FTA-ABS, Rh blood group, Red cell antibodies, HIV (opt-out) | Baseline health; carrier detection; infection screening |
| 11–13⁺⁶ weeks | 1st trimester combined DS screening (nuchal translucency + PAPP-A + free β-hCG) | Down syndrome risk assessment (preferred) |
| 16–19⁺⁶ weeks | 2nd trimester biochemical DS screening (quad screen: AFP, hCG, uE₃, inhibin A) | DS screening if booked late / missed 1st trimester window |
| 18–22⁺⁶ weeks | Morphology (anomaly) scan | Structural anomaly detection |
| 26–30 weeks | 75g OGTT | Gestational diabetes screening |
| 35–37 weeks | GBS (Group B Streptococcus) screening | Intrapartum antibiotic prophylaxis if positive |
Service caveat: current Hong Kong public information describes OGTT, GBS testing and structural ultrasound as being offered when necessary or according to the individual's condition/local service, rather than guaranteeing every item to every patient. The gestational windows remain useful exam anchors, but actual care follows the responsible obstetric unit. [19]
Timing Matters
If a woman books late (after 14 weeks), she cannot have 1st trimester combined screening → offer 2nd trimester biochemical screening at 16–19⁺⁶ weeks instead. This was explicitly noted in the lecture: "Or biochemical screening when 16–19 weeks if booked late." [1]
1st trimester combined screening (11–13⁺⁶ weeks):
- Nuchal translucency (NT) on ultrasound: thickened NT ( > 3.5 mm) → increased risk. NT reflects fluid accumulation behind the fetal neck — seen in chromosomal abnormalities, cardiac defects, and other conditions.
- PAPP-A (pregnancy-associated plasma protein A): LOW in Down syndrome
- Free β-hCG: HIGH in Down syndrome
- Combined with maternal age → risk calculation
- Detection rate ~85–90% with 5% false positive rate
2nd trimester biochemical screening (16–19⁺⁶ weeks):
- AFP: LOW in DS (high in NTD)
- hCG: HIGH in DS
- Unconjugated estriol (uE₃): LOW in DS
- Inhibin A: HIGH in DS
- Detection rate ~80% with 5% FPR
Screen positive → counselling about second-tier NIPT and/or diagnostic testing, depending on the pathway and informed choice.
Non-invasive prenatal testing (NIPT / cell-free DNA):
- Analyses cell-free DNA in maternal plasma that is predominantly placental in origin (hence placental mosaicism can cause discordance)
- High sensitivity and specificity for trisomies 21, 18, 13
- It is a screening test, not diagnostic — positive results must be confirmed by invasive testing
- In the HA pathway described by current Family Health Service information, it is a second-tier screen after a positive first-tier test. A high-risk or non-reportable NIPT result is followed by counselling for diagnostic confirmation; patients may also discuss direct diagnostic testing. [20]
Fetal morphology scan at 18–22 weeks [1]
This is a systematic ultrasound survey of fetal anatomy to detect structural anomalies:
- Fetal number, lie, growth/biometry and viability
- Brain in standard planes (ventricles, cavum septi pellucidi, thalami, cerebellum and cisterna magna)
- Face (profile, orbits and upper lip; the palate is more difficult to assess)
- Spine
- Heart (four-chamber view, outflow tracts)
- Abdomen and abdominal wall (stomach, cord insertion, omphalocele, gastroschisis)
- Kidneys and bladder
- Long bones and extremities
- Placental location, amniotic fluid and cervix where indicated
The montage on slide 29 is a checklist, not a collection of isolated “normal pictures”: each labelled image is a required plane or structure. A normal morphology scan reduces but does not eliminate the possibility of a structural, genetic or later-developing functional disorder. Current HK information advises a fetal morphology scan after a negative Down syndrome screen but notes that public-sector availability may be limited. [20]
Prenatal Diagnosis [1]
The objective of diagnosing disorders is to help affected individuals by offering timely treatment, to prevent irreversible damage, or support, if treatment is unavailable. [1]
The lecture provides a detailed flowchart:
Referral → Counselling → Diagnosis (imaging + sampling when indicated + laboratory testing) → Results:
- Normal result → continue pregnancy, while remembering the residual risk outside the test's scope.
- Uncertain result → variant/uncertainty-specific counselling, possible parental or additional testing, and a plan for antenatal/postnatal review.
- Abnormal result → counselling about condition-specific options: continuation with planned neonatal treatment/support, fetal treatment where available, or lawful termination.
- Prenatal/postnatal discrepancy → paediatric assessment and a confirmation study; do not assume that either result is automatically the correct one.
This is the important meaning of slides 31 and 35: diagnosis is not the endpoint. Every branch returns to counselling, delivery planning, treatment or follow-up.
Invasive tests: Chorionic villus sampling (CVS), Amniocentesis, Cordocentesis. Chromosomal test +/- molecular genetic test as indicated. [1]
| Feature | CVS | Amniocentesis |
|---|---|---|
| Timing | 11–14 weeks | 16–20 weeks |
| Sample | Chorionic villi | Amniocytes from amniotic fluid |
| Lab test | Cytogenetic studies (karyotype/CMA) | Cytogenetic studies (karyotype/CMA) |
| Pain relief | Local analgesia | Not required |
| Miscarriage risk | 0.1–0.2% | 0.1–0.2% |
| Culture failure rate | < 1% | < 1% |
| Turnaround for CMA | 7 working days | 7 working days |
| Maternal risk | Minimal | Minimal |
The procedural diagrams clarify what is sampled under continuous ultrasound guidance:
- CVS: a transabdominal needle takes placental chorionic villi; it does not enter the fetal body. Earlier access is its main advantage, while a placental result can occasionally be complicated by confined placental mosaicism.
- Amniocentesis: a needle enters an amniotic-fluid pocket while avoiding the fetus and placenta; shed fetal cells in the fluid are analysed.
The quoted 0.1–0.2% miscarriage figures are the lecture's procedure-related estimates, not a promise for every centre or patient. Risk varies with operator, indication and background pregnancy risk; consent should use the performing unit's current figures.
A normal report does not guarantee that the fetus is free from disorders that are not chromosomal in origin. [1]
Both tests are very accurate. A small proportion of test results may show mosaicism which may require further investigation. [1]
Key Exam Point: Limitations of Invasive Testing
Students often assume a normal karyotype means a normal baby. The lecture explicitly states this is NOT the case. Chromosomal testing does not detect single-gene disorders (unless specifically tested), structural anomalies, or functional problems. Mosaicism can also complicate interpretation — confined placental mosaicism in CVS may not reflect the true fetal karyotype.
Cordocentesis (fetal blood sampling):
- Usually from umbilical vein under USG guidance
- From ~18 weeks onwards
- Used for rapid karyotyping, Hb studies (e.g., α-thal confirmation), fetal infection workup
- Higher miscarriage risk (~1–2%) than CVS/amniocentesis
For α-thalassaemia when both parents carry a clinically significant α⁰ allele:
- Define the parental variants/phase, then offer targeted fetal molecular diagnosis using CVS or amniocentesis at the appropriate gestation.
- Ultrasound surveillance can look for anaemia/hydrops (cardiomegaly, placentomegaly, effusions/ascites/skin oedema, growth restriction and raised middle cerebral artery peak systolic velocity), but waiting for hydrops is not a substitute for early molecular diagnosis.
- If Hb Bart's disease is confirmed, non-directive counselling should include termination, expectant/palliative pathways and—where expertise exists—fetal blood sampling and intrauterine transfusion, with the expectation of ongoing postnatal transfusion care for survivors. [22]
For β-thalassaemia (both parents carriers):
- DNA study of parents first to identify mutations
- If mutations identified → CVS (1st trimester) or amniocentesis (2nd trimester) for DNA mutation analysis
- If familial variants cannot be defined, explain the limits of prenatal exclusion and seek specialist laboratory/genetic advice [6]
When a significant risk is identified, couples should be counselled about their reproductive options:
- Natural conception with prenatal diagnosis — accept risk, plan for screening/diagnosis during pregnancy
- Pre-implantation genetic testing (PGT) with IVF — embryos tested before transfer; avoids termination dilemma
- Donor gametes — if one partner has a dominant condition or both are carriers
- Adoption — an option to discuss
- Choosing not to have biological children — valid choice
- Pregnancy continuation with preparation — for conditions compatible with life, plan for neonatal management
- Pregnancy termination — offered when severe anomaly diagnosed; legal framework in HK applies
Counselling Concerns [1]
Counsel = explain, enable others to decide. Advise = explain, recommend a course of action. [1]
This distinction is critical. In genetic/prenatal counselling, the approach should be non-directive — you provide information and support the couple's autonomous decision-making. You do NOT tell them what to do.
Improving the chance of having a healthy child: Prepare before conception; Screen or test after conception; Current tests cannot guarantee a healthy baby for every pregnancy. [1]
Help couples choose the type of screening or diagnostic test that best suits their need. Help couples understand the impact of fetal condition on the family. Help couples choose the course of action for management of fetal abnormality that they will not regret. [1]
Autonomy (informed consent, non-directive counselling, full disclosure, voluntary), Nonmaleficence, Beneficence, Justice (indicated, accessible). [1]
| Principle | Application in Prenatal Counselling |
|---|---|
| Autonomy | Couple makes the final decision; all options presented including continuation of pregnancy; testing is voluntary; informed consent with understanding of risks/benefits/limitations |
| Non-maleficence | Minimise harm — e.g., miscarriage risk of invasive testing; psychological harm of uncertain results |
| Beneficence | Acting in best interest of mother and fetus — early diagnosis allows treatment planning |
| Justice | Fair access to screening regardless of socioeconomic status; publicly funded screening available |
With severe anomaly — may be offered as an option. Refer for second opinion if doctor has conscientious objection to pregnancy termination. [1]
Legal requirements in HK (from CFB OG03): [7]
- Requires opinion of two registered practitioners formed in good faith that:
- (a) Continuance of pregnancy would involve greater risk to the pregnant woman's life, or of injury to her physical or mental health, than termination, OR
- (b) There is substantial risk that the child would suffer from such physical or mental abnormality as to be seriously handicapped
- Treatment must normally be carried out in a government or approved hospital/clinic. [24]
- A pregnancy over 24 weeks is not authorized on fetal-anomaly grounds alone; it requires two registered practitioners to consider termination immediately necessary to save the pregnant woman's life. The Department of Health provides a specific section 47A(2C) certificate (Form 2A). Court authorization is not the statutory route described here. [23]
Integration with Related Topics
The examples below are prompts for a specialist medication review, not automatic substitutions:
| Condition | Medicine of concern | Planning issue | |---|---|---|---| | Epilepsy/bipolar disorder | Valproate and other antiseizure medicines | Review indication, seizure/relapse risk, alternatives, dose and pregnancy-prevention requirements with the relevant specialist; never stop abruptly [16] | | Hyperthyroidism | Carbimazole/methimazole or PTU | Balance embryopathy risk against PTU hepatotoxicity and disease control; agree trimester-specific treatment and monitoring with endocrinology/obstetric medicine [2] | | Hypertension | ACE inhibitor/ARB | Plan an appropriate alternative before conception where possible; do not leave severe hypertension untreated | | Thrombosis/mechanical valve | Warfarin | Anticoagulation choice and timing depend on indication and thrombosis risk; mechanical valves need a multidisciplinary plan [4] | | Autoimmune/transplant disease | Mycophenolate, methotrexate and other disease-modifying medicines | Arrange a safe alternative and adequate washout while maintaining disease control | | Mental illness | Lithium, antidepressants and antipsychotics | Compare fetal/neonatal risks with relapse and suicide risk; avoid abrupt withdrawal or reflex switching |
The 2023 SAQ tested: "Name one routine antenatal investigation for pregnant woman at 28 weeks and specify what condition to rule out." Answer: 75g OGTT to screen for gestational diabetes mellitus.
- Opt-out screening at booking
- Start or continue effective antiretroviral therapy (ART) promptly and monitor HIV RNA, including near delivery.
- The older three-drug intrapartum line in the source notes is obsolete. Current NIH guidance continues the regular ART regimen in labour and bases IV zidovudine and HIV-indicated caesarean birth on near-delivery viral load and adherence (recommended when HIV RNA is > 1,000 copies/mL or unknown; IV zidovudine is not routinely required with HIV RNA < 50 copies/mL and good adherence). [25]
- Neonatal prophylaxis and virologic testing are risk-stratified by the paediatric/HIV team.
- Formula or pasteurized donor milk eliminates postnatal transmission. Some current guidelines support shared decision-making about breastfeeding for a parent with sustained suppression on ART, with intensive maternal/infant follow-up; the residual transmission risk is less than 1% but not zero. Follow the current Hong Kong specialist policy rather than a blanket historical rule. [26]
The GP lecture on sexual problems covers counselling during pre-marital checks:
- Results of investigations
- The process of sexual intercourse — private, comfortable environment
- Attitude: respect, tenderness — not being a "spectator"
- Communication and foreplay
- Responsibility to initiate and respond
- Understanding prejudices and unrealistic expectations
- Fatigue as a common barrier
- Hymen — addressing myths and concerns
From the 2022 MCQ: "If the pregnancy is normal, and there are no signs of miscarriage, women can have sexual intercourse during pregnancy." — This is the correct answer. [13]
High Yield Summary
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Pre-pregnancy counselling
- aims to optimize maternal health, identify genetic/medical risks, adjust teratogenic medications, ensure vaccinations, supplement folate, and modify lifestyle BEFORE conception.
- Risk identification uses detailed history (age, ethnicity, consanguinity, family Hx, medical Hx, meds, obstetric Hx, lifestyle), examination (BP, BMI, heart sounds, cervical screening), and screening tests (CBP with MCV, blood group/Rh, VDRL, HBsAg, rubella Ab, HIV, urine).
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Thalassaemia screening
- is the most tested genetic condition: current HK public guidance uses maternal MCV ≤80 fL → partner testing → specialist haemoglobin/molecular work-up if both are low. Later lecture slides use < 82 fL, so recognize the deck discrepancy. α-thalassaemia trait typically has normal HbA₂; β-thalassaemia trait typically has raised HbA₂.
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Antenatal screening schedule
- Lecture sequence: booking bloods → first-tier Down syndrome screening (11–13⁺⁶ weeks, or 16–19⁺⁶ weeks if booked late) → morphology scan (18–22⁺⁶ weeks) → OGTT (26–30 weeks) → GBS (35–37 weeks). A positive first-tier screen is followed by counselling about second-tier NIPT and/or diagnosis; a high-risk/non-reportable NIPT needs invasive confirmation.
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Invasive testing
- CVS (11–14 weeks) samples placenta; amniocentesis (16–20 weeks) samples amniotic fluid. The deck quotes a 0.1–0.2% procedure-related miscarriage risk for each. A normal result does NOT guarantee a healthy baby.
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Counselling is non-directive
- explain, enable the couple to decide. Ethical principles: autonomy, non-maleficence, beneficence, justice. Termination for severe anomaly may be offered; refer if conscientious objection.
Active Recall - Lecture Notes
[1] Lecture slides: GC 113. Can we get married Pre-marital, pre-pregnancy and pre-natal counselling.pdf (all pages) [2] Senior notes: Block A - I am losing weight and sweating all the time_ causes of severe, weight loss; thyrotoxicosis; hypothyroidism.pdf (p19) [3] Senior notes: Block A - Many members of the family have anaemia.pdf (p10) [4] Senior notes: Block A - Leg swelling and chest pain_ deep vein thrombosis; pulmonary embolism; Thrombophilia.pdf (p19) [5] Senior notes: Maksim Medicine Notes.pdf (p259) [6] Senior notes: MBBS Final MB (Pediatrics) (Felix PY Lai).pdf (p588-589); MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1348-1349) [7] Lecture slides: CFB (OG03) Fertility Regulation.pdf (p6) [9] Past papers: 2023 Fourth Summative MCQ.pdf (Q86, p33) [10] Past papers: 2023 Fourth Summative SAQ.pdf (Q2, p3) [11] Senior notes: MBBS Final MB (Medicine) (Felix PY Lai).pdf (p1070) [12] Lecture slides: MBBS4 t Sexual problems in GP160925.pdf (p24) [13] Past papers: 2022 Fourth Summative MCQ.pdf (Q7, p4) [14] Hong Kong Family Health Service: Healthy Eating During Pregnancy and Breastfeeding (revised February 2025; reprinted February 2026) [15] NICE NG247: Maternal and child nutrition — folic acid recommendations (2025) [16] UK MHRA: Valproate — reproductive risks (updated safety guidance) [17] US FDA: Removal of the strongest statin pregnancy warning; individualized risk-benefit advice (2021) [18] Hong Kong Centre for Health Protection: Seasonal influenza vaccination for pregnant women [19] Hong Kong Family Health Service: Antenatal check-up schedule and points to note [20] Hong Kong Family Health Service / Hospital Authority: Prenatal Screening for Down Syndrome [21] Hong Kong Family Health Service: Mean Cell Volume & Thalassaemia [22] Thalassaemia International Federation: Guidelines for the Management of α-Thalassaemia — prenatal Hb Bart's hydrops fetalis (2023) [23] Hong Kong Department of Health: Termination of Pregnancy — statutory certificates including Form 2A [24] Hong Kong Office for Regulation of Private Healthcare Facilities: Approved hospitals/clinics under Cap. 212 section 47A(3) [25] US NIH Perinatal HIV Guidelines: Intrapartum Care for People With HIV [26] US NIH Perinatal HIV Guidelines: Preventing HIV Transmission During Infant Feeding [27] RCOG Green-top Guideline No. 17: Recurrent Miscarriage (2023)
GC112 Abnormal Vaginal Bleeding Gynaecological Cancer
Abnormal vaginal bleeding in the context of gynaecological cancer refers to irregular, postmenopausal, or otherwise unexplained uterine or vaginal bleeding that may signal an underlying malignancy of the endometrium, cervix, ovary, vagina, or vulva, warranting urgent investigation.
GC114 Climacteric Symptoms Menopause And Related Illness; Amenorrhoea
Climacteric symptoms encompass the vasomotor, psychological, and urogenital manifestations arising from ovarian hormone decline during the menopausal transition, while amenorrhoea refers to the absence of menstruation due to physiological, pathological, or iatrogenic causes.