## Investigations at the Booking Visit **Key Point:** AFP is NOT a routine booking visit investigation. Maternal serum screening for chromosomal abnormalities (including AFP) is performed as part of **second-trimester screening** (15–20 weeks) or **first-trimester combined screening** (11–14 weeks), not at the initial booking visit. ### Standard Booking Visit Investigations | Investigation | Purpose | Timing | | --- | --- | --- | | Blood group & antibody screen | Identify blood type and unexpected antibodies | Booking visit | | Full blood count | Baseline haemoglobin, detect anaemia | Booking visit | | Infectious serology (HIV, syphilis, HBsAg, HCV) | Identify maternal infections | Booking visit | | Blood glucose (fasting/random) | Screen for gestational diabetes risk | Booking visit | | Urine culture | Detect asymptomatic bacteriuria | Booking visit | | Blood pressure & weight | Baseline vital signs | Booking visit | | **First-trimester combined screening** | Nuchal translucency + PAPP-A + β-hCG | 11–14 weeks (separate visit) | | **Second-trimester serum screening** | AFP, hCG, uE3, inhibin A | 15–20 weeks (if not done in first trimester) | ### Why AFP is Not at Booking **High-Yield:** AFP levels vary significantly with gestational age. Accurate dating (confirmed by first-trimester ultrasound) is essential before interpreting AFP. Therefore, serum screening is deferred to 15–20 weeks (second trimester) or done as part of first-trimester combined screening (11–14 weeks with ultrasound), not at the initial booking visit. **Mnemonic:** **BASIC** investigations at booking — **B**lood group, **A**ntibody screen, **S**erology (infectious), **I**nfections (urine culture), **C**omplete blood count.
Sign up free to access AI-powered MCQ practice with detailed explanations and adaptive learning.