Quad Screening with PLGF

The quad screen is a second‑trimester maternal blood test that measures four substances—AFP, hCG, unconjugated estriol and inhibin A. It’s primarily used to screen for chromosomal and neural‑tube issues, but abnormal levels can also suggest placental dysfunction and a higher risk of preeclampsia. It’s a risk assessment, not diagnostic; abnormal results prompt closer monitoring and further evaluation.

The quad screen is a second‑trimester maternal blood test measuring four substances: alpha‑fetoprotein (AFP), human chorionic gonadotropin (hCG), unconjugated estriol (uE3), and inhibin A. Performed generally between 15–20 weeks’ gestation, results are combined with maternal and gestational age to estimate risks for neural tube defects, Down syndrome (trisomy 21), and trisomy 18.

A PlGF blood test measures placental growth factor — a protein produced by the placenta — in maternal blood. Low PlGF (or a raised sFlt‑1/PlGF ratio) indicates placental dysfunction and helps diagnose or predict preeclampsia. It aids clinical decisions on monitoring, treatment, and timing of delivery in pregnant women, especially after 20 weeks or when hypertension or related symptoms occur.

Placental growth factor (PlGF) normally rises after conception, peaking in the late second–early third trimester. Typical mid-pregnancy concentrations are roughly 100–600 pg/mL, varying by gestational age and assay. Levels below about 100 pg/mL (especially before 35 weeks) are considered low and raise concern for placental dysfunction or pre-eclampsia; interpretation should use gestation-specific reference ranges.

A positive quad screen means your pregnancy is at higher-than-average risk for conditions like Down syndrome, trisomy 18, or neural tube defects — it’s not a diagnosis. Next steps usually include detailed ultrasound to confirm dates and anatomy, noninvasive cell‑free DNA screening or genetic counseling, and, if desired, diagnostic testing (CVS or amniocentesis) to confirm any abnormality. Discuss options with your provider.

The diagnosis of preeclampsia is confirmed by two tests: (1) repeated blood‑pressure measurements showing new hypertension (≥140/90 mmHg after 20 weeks’ gestation) and (2) testing for proteinuria — ideally a urine protein/creatinine ratio ≥30 mg/mmol or a 24‑hour urine protein ≥300 mg. If proteinuria is absent, new organ dysfunction (abnormal platelets, creatinine or liver enzymes) can substitute.