A 28-year-old primigravida presents for her first antenatal visit at 12 weeks of gestation. She is asymptomatic with a regular menstrual history. On examination, her blood pressure is 118/76 mmHg, weight 62 kg, and height 160 cm (BMI 24.2 kg/m²). Urine dipstick is normal. She has no significant past medical or obstetric history. Which of the following investigations is NOT routinely recommended at this first trimester booking visit according to current antenatal care guidelines?

Explanation

## Routine First Trimester Antenatal Investigations **Key Point:** Serum AFP and uE3 are second trimester screening markers (15–20 weeks), NOT first trimester investigations. They form part of the triple or quadruple screen in the second trimester. ### First Trimester Booking Visit Investigations (12–14 weeks) | Investigation | Indication | Timing | | --- | --- | --- | | Blood group & antibody screen | Identify blood type and red cell antibodies | Booking visit | | Full blood count | Screen for anaemia, thrombocytopenia | Booking visit | | Blood glucose (fasting/random) | Screen for gestational diabetes risk | Booking visit | | Infectious disease serology | HIV, syphilis (RPR/VDRL), hepatitis B, C | Booking visit | | Nuchal translucency ultrasound | First trimester aneuploidy screening | 11–14 weeks | | PAPP-A & free β-hCG | First trimester biochemical screening | 11–14 weeks | | Thyroid function (TSH) | Screen for hypothyroidism | Booking visit | **High-Yield:** AFP and uE3 are measured in the *second trimester* (15–20 weeks) as part of the triple screen (AFP, uE3, hCG) or quadruple screen (adding inhibin A). They are NOT part of first trimester screening. ### First Trimester Aneuploidy Screening The combined screening at 11–14 weeks uses: 1. Nuchal translucency (NT) measurement on ultrasound 2. Serum PAPP-A (pregnancy-associated plasma protein A) 3. Free β-human chorionic gonadotropin (β-hCG) These are combined with maternal age to calculate risk for trisomy 21, 18, and 13. **Clinical Pearl:** A patient presenting at 12 weeks should have first trimester combined screening (NT + biochemistry) offered, NOT second trimester markers yet. If she returns at 15–20 weeks, then AFP and uE3 become relevant. **Mnemonic:** FIT screening = **F**irst trimester **I**nvestigations at **T**welfth week: NT ultrasound, PAPP-A, free β-hCG, plus routine bloods (FBC, glucose, serology, blood group).