The quad screen is a second‑trimester maternal blood test measuring AFP, hCG, unconjugated estriol and inhibin‑A to screen for chromosomal abnormalities and neural tube defects. Abnormal levels—particularly high inhibin‑A or altered hCG/estriol—can be associated with higher preeclampsia risk, but the quad screen does not diagnose preeclampsia. Diagnosis relies on blood pressure, urine protein and targeted biomarkers/monitoring.

There isn’t a “first‑trimester quad” test. First‑trimester screening (around 10–13+6 weeks) uses maternal blood for PAPP‑A and free β‑hCG plus ultrasound nuchal translucency to estimate risk of Down syndrome and trisomy 18. The quad screen is a separate second‑trimester blood test (15–20 weeks) measuring AFP, hCG, estriol and inhibin A to assess neural‑tube defects and chromosomal risk.

First-trimester preeclampsia screening, performed around 11–14 weeks, combines maternal history and demographics, mean arterial blood pressure, uterine artery Doppler, and blood biomarkers (PAPP-A and placental growth factor) to calculate individualized risk of preeclampsia. Identifying high-risk pregnancies allows early interventions such as low-dose aspirin and closer monitoring to reduce severe outcomes for mother and baby.

A “first‑trimester quad without preeclampsia” means a first‑trimester screening panel (four biomarkers and/or ultrasound measures) showed no signal of increased preeclampsia risk. First‑trimester screens mainly assess chromosomal anomalies; some include placental markers to estimate preeclampsia risk. A negative result indicates normal blood‑pressure/proteinuria findings and low biochemical risk, but routine antenatal monitoring and follow‑up are still recommended.

If your quad screen is positive (high‑risk), it indicates an increased chance of chromosomal conditions or neural tube defects—not a definitive diagnosis. Your provider will recommend follow‑up: detailed ultrasound, noninvasive prenatal testing (cell‑free DNA), and, if needed, diagnostic testing (CVS or amniocentesis). Factors like gestational age, maternal weight, twins, or diabetes can influence results. Genetic counseling and emotional support are advised.

Preeclampsia is confirmed by two key tests: measurement of maternal blood pressure showing new‑onset hypertension (≥140/90 mmHg on two occasions) and demonstration of proteinuria, usually by a urine protein‑to‑creatinine ratio ≥0.3 or a 24‑hour urine protein ≥300 mg (or dipstick ≥1+ if unavailable). These are assessed after 20 weeks’ gestation.