Maternal disease, medication and substance effects on the fetus — branching viva

Station opening

Examiner: "A pregnant woman has been exposed to a number of agents. Before we go to specifics, give me your framework for thinking about how maternal exposures affect the fetus." [1]

Strong candidate (must-hit)

• Teratogenic harm is timing-dependent: all-or-none in the first two weeks, structural defects in organogenesis weeks 3 to 8, growth and neurodevelopmental effects from week 9. [1]
• Harm is classified as structural, growth, functional or neurodevelopmental, or neonatal adaptation and withdrawal. [1]
• Prevention is folic acid for all and high-dose for high-risk, magnesium sulfate under 30 weeks, and pre-conception switching of known teratogens. [2]

Weak candidate

• "Everything in pregnancy is dangerous." [1]

Branch A — Valproate at 8 weeks

Examiner: "A woman on valproate for epilepsy is 8 weeks pregnant and asks whether to stop it. What do you do?" [9]

Strong

• Does NOT stop abruptly — uncontrolled seizures carry their own fetal risk. [9]
• Urgent neurology and perinatal referral; consider switch to lamotrigine or levetiracetam where the epilepsy allows. [9]
• Names fetal valproate spectrum disorder: neural tube, cardiac, neurodevelopmental harm including autism risk. [11]
• Confirms high-dose folic acid 5 mg and plans detailed anatomy scan and fetal echo. [2]

Weak

• "Stop the valproate immediately." [9]

Branch B — Infant of a diabetic mother

Examiner: "A term 4.3 kg infant of a type 1 diabetic mother is jittery at 2 hours with glucose 1.6 mmol/L. Walk me through your reasoning and immediate management." [5]

Strong

• Explains fetal hyperinsulinaemia from maternal hyperglycaemia as the mechanism of neonatal hypoglycaemia. [4]
• Immediate management: early feeding, repeat glucose per protocol, buccal dextrose gel and recheck, IV 10 percent dextrose if below threshold. [5]
• Names structural risk (cardiac, caudal regression, neural tube, renal) tied to periconception HbA1c, and plans cardiac examination and developmental follow-up. [4] [5]

Weak

• "Give a glucose bolus and recheck." [5]

Branch C — Warfarin embryopathy

Examiner: "A woman on warfarin for a mechanical heart valve delivers a term infant with nasal hypoplasia and stippled epiphyses. What syndrome is this and what is the mechanism?" [16]

Strong

• Names fetal warfarin syndrome. [16]
• Mechanism: warfarin crosses placenta, inhibits vitamin-K-dependent proteins including osteocalcin, disrupting fetal bone mineralisation. [16]
• Switches the message: heparin and LMWH do not cross the placenta and are the safe anticoagulant in pregnancy; pre-conception switch is the prevention. [16]

Weak

• "This is congenital infection." [16]

Branch D — Opioid withdrawal with a mimic

Examiner: "An infant of a mother on methadone is irritable and tremulous at 48 hours. The nurse asks you to start morphine. What is your approach?" [27]

Strong

• First excludes the dangerous mimics: sepsis, hypoglycaemia, hypocalcaemia, metabolic disease, intracranial haemorrhage. [27]
• Uses a validated assessment tool (Finnegan or Eat-Sleep-Console) rather than a one-off impression. [27]
• Starts with non-pharmacological care: rooming-in, breastfeeding if safe, swaddling, low-stimulation environment. [27]
• Pharmacological treatment (oral morphine or methadone) reserved for infants who fail functional assessments or reach score thresholds. [27]

Weak

• "Start morphine immediately, it is withdrawal." [27]

Close

Examiner: "Summarise your approach to a pregnant woman exposed to a potential teratogen in one sentence." [1]

Strong

• "I take a full exposure history, I match the exposure to the gestational window to estimate the likely harm, I never stop an essential medication abruptly without specialist advice, I optimise prevention with folate and where relevant magnesium sulfate, and I arrange targeted antenatal and neonatal surveillance with developmental follow-up." [1] [2]

Weak

• "Refer to obstetrics." [1]