Gestational Age & Milestones
Interprets gestational age in weeks to identify viability, anomaly scan, and term thresholds.
Score interpretation
< 12 weeks: First trimester. Dating USS (10–13+6 weeks). NT / first trimester combined screening 11–13+6 weeks.
→ Booking bloods + USS. Combined screening offered 11–13+6 weeks (NT + PAPP-A + hCG).
12–20 weeks: Early second trimester. Anomaly scan at 18–21+6 weeks.
→ Anomaly USS 18–20+6 weeks. Quadruple screening 15–20 weeks if first trimester screening missed.
20–23+6 weeks: Pre-viability / periviability. Limit of viability ~22–24 weeks (institution dependent).
→ Discuss viability thresholds. Specialist fetal medicine input for any concerns. Fetal growth surveillance.
24–27+6 weeks: Viable preterm. Neonatal intensive care support required for any delivery.
→ If threatened preterm labour: IM betamethasone 2 doses 12–24h apart. Tocolysis to allow steroid completion. Neonatal team discussion. MgSO₄ for neuroprotection if <30 weeks.
28–36+6 weeks: Preterm gestation. SCBU/NNU support required.
→ Steroids if <34 weeks. Growth USS. GBS swab at 35–37 weeks if planned vaginal delivery.
37–41+6 weeks: Term gestation. Full neonatal maturity expected.
→ Membrane sweep offered from 39 weeks. Induction offered at 41+0 to 42+0 (NICE). Routine antenatal monitoring.
≥42 weeks: Post-dates pregnancy. Increased risk of stillbirth and meconium aspiration.
→ Induction should have been offered by 42 weeks (NICE NG207). Discuss risks. Enhanced monitoring if declined.
Interpretation bands for the Gestational Age. Apply clinical judgement and local guidance.
References
- NICE NG201. Antenatal care. 2021.
- NICE NG207. Inducing labour. 2021.
Related
Curated clinical cross-links plus same-class fallbacks.
- Betamethasone (Antenatal Corticosteroids) · Corticosteroid (Fetal Lung Maturation)
- Hydroxyprogesterone Caproate / Progesterone (Preterm Birth Prevention) · Progestogen (Preterm Birth Prevention)
- Metformin (Gestational Diabetes / PCOS) · Biguanide — Gestational Diabetes / PCOS
- Dexamethasone (Antenatal / OHSS / CAH) · Corticosteroid — Obstetric and Gynaecological
- Fluconazole (Paediatric) · Triazole Antifungal — Candida / Fungal Prophylaxis in Preterm Neonates
- Spinal Anaesthesia Hypotension Management · AAGBI; ASA
- Pre-Eclampsia / Eclampsia in ED · NICE NG133; RCOG Green-top 10A
- Suspected Ectopic Pregnancy · NICE NG126; RCOG Green-top 21
- Polycystic Ovary Syndrome (PCOS) · International PCOS Guideline 2023; NICE CKS
- Pre-eclampsia Management · NICE NG133 2019
- Ectopic Pregnancy · NICE CG154 / RCOG GTG 21
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.