First-Trimester Preeclampsia Screening — Prevention Through Early Identification
Preeclampsia is largely preventable. The FMF (Fetal Medicine Foundation) first-trimester screening algorithm identifies high-risk women at 11–13 weeks, allowing low-dose aspirin started before 16 weeks to reduce preterm preeclampsia by 60–70% (ASPRE trial). This is one of the highest-impact interventions in modern obstetrics.
What is Preeclampsia?
A multi-system pregnancy disorder characterised by new-onset hypertension (BP ≥140/90) after 20 weeks, accompanied by proteinuria or end-organ dysfunction. Severe forms threaten maternal life (eclamptic seizures, HELLP syndrome, stroke, organ failure) and fetal life (growth restriction, abruption, stillbirth, iatrogenic preterm birth). Globally responsible for substantial maternal and perinatal mortality.
The FMF First-Trimester Screening Algorithm
Performed at 11–13 weeks 6 days. Combines: maternal characteristics (age, BMI, ethnicity, parity, prior pregnancy history, family history, chronic conditions), mean arterial pressure (MAP), uterine artery pulsatility index (Doppler), maternal serum PAPP-A and PlGF. Algorithm computes individualised risk for preterm (<37 weeks) and term preeclampsia. Detects approximately 90% of preterm preeclampsia at a 10% false-positive rate.
Low-Dose Aspirin Prophylaxis — Evidence Base
The ASPRE trial demonstrated that high-risk women identified by FMF screening, started on aspirin 150mg at bedtime before 16 weeks and continued until 36 weeks, had a 62% reduction in preterm preeclampsia. Mechanism: improved placental development through anti-platelet and anti-inflammatory effects. Safe for both mother and baby at this dose.
Why First-Trimester Screening Matters
After 16 weeks, the window for preventive aspirin closes. Late-pregnancy preeclampsia detection only allows management of established disease, not prevention. First-trimester screening identifies the women who benefit MOST from prophylaxis — those at risk of severe, early-onset preeclampsia.
What If Screening Shows High Risk?
Low-dose aspirin started before 16 weeks. Intensified BP monitoring throughout pregnancy. Serial growth scans (28, 32, 36 weeks minimum). Doppler studies of uterine and umbilical arteries. Patient education on warning symptoms (severe headache, visual disturbances, upper abdominal pain, sudden swelling). Most high-risk women still have uncomplicated pregnancies — the prophylaxis works.
Frequently Asked Questions
Should every pregnant woman have first-trimester preeclampsia screening?
Yes — universal screening is recommended by FIGO and ISUOG. The intervention (aspirin) is so effective that identifying the 10–15% at highest risk is high-yield public health.
Is aspirin safe in pregnancy?
Low-dose aspirin (75–150 mg) is well-established as safe in pregnancy. It is one of the most evidence-supported preventive interventions in modern obstetrics, with proven benefit and minimal risk at this dose.
When should aspirin be started?
Before 16 weeks — ideally between 12 and 14 weeks. Started after 16 weeks, the preventive effect is significantly reduced.
How long should aspirin be continued?
Until 36 weeks for preeclampsia prevention. Some protocols continue until delivery for other indications.
What if my first-trimester screening is low risk?
You do not need aspirin. Standard antenatal care continues with routine BP monitoring at each visit. Low-risk screening does not eliminate possibility (no test is perfect) but most women in this group will have normotensive pregnancies.
I had preeclampsia in a previous pregnancy — am I high risk?
Yes. Prior preeclampsia is one of the strongest risk factors. Most international guidelines recommend aspirin prophylaxis for any woman with prior preeclampsia, regardless of FMF screen result.
Dr. Priyadatt Patel
Senior Gynecologist · Advanced Laparoscopic Surgeon · IVF and Endometriosis Programme Lead
MS OBGyn · Pregnancy Care · Advanced Gynaecological Ultrasound · Fertility Preservation
ESHRE / ESGE / AAGL / ASRM guideline-aligned practice. 3D Karl Storz precision technique. Fertility-preservation-first philosophy. Evidence-based decisions, honest counselling, long-term outcomes orientation.
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