Issue 3/2026
Iskilieva, М.
„Dr. Shterev” Hospital – Sofia
Third-trimester screening is an integral component of contemporary evidence-based prenatal care, aimed at reassessing the risk of late-onset obstetric complications associated with placental dysfunction, fetal growth restriction (FGR), and preeclampsia. In uncomplicated pregnancies, the optimal time window for assessment is between 35+0 and 36+6 weeks of gestation, when diagnostic accuracy for evaluating fetal growth and hemodynamic is higher.
The screening protocol includes detailed ultrasound evaluation of fetal anatomy and biometry, with calculation of estimated fetal weight (EFW) to identify small-for-gestational-age (SGA) and large-for-gestational-age (LGA) fetuses, as well as those with FGR. Amniotic fluid volume is assessed as an indirect marker of fetoplacental function, alongside placental morphology and location. Doppler velocimetry of the umbilical artery, middle cerebral artery, and ductus venosus provides an information about fetoplacental perfusion and contributes early detection of fetal hypoxia.
The integration of angiogenic biomarkers (placental growth factor [PlGF] and soluble fms-like tyrosine kinase-1
[sFlt-1]) and multiparametric algorithms for preeclampsia risk stratification significantly improves the predictive performance of third-trimester screening.
Early identification of high-risk pregnancies permit individualized monitoring and optimized delivery planning and consequently contributing to the reduction of maternal and perinatal morbidity and mortality.
Key words: third trimester, preeclampsia, prenatal screening, placental function
Address for correspondence:
Dr. Marieta Iskilieva,
AG specialist in fetal medicine – Sofia
Dr. Shterev Medical Complex
е-mail: m.iskilieva@gmail.com