Second and third trimester fetal ultrasound population screening for risks of preterm birth and small-size and large-size for gestational age at birth: a population-based prospective cohort study
Related Experiment Video
Updated: Dec 24, 2025
High Frequency Ultrasound for the Analysis of Fetal and Placental Development In Vivo
Published on: November 8, 2018
Jan S Erkamp1,2, Ellis Voerman1,2, Eric A P Steegers3
1The Generation R Study Group, Erasmus MC, University Medical Center Rotterdam, P.O. Box 2040, 3000, CA, Rotterdam, the Netherlands.
Insights
Third trimester ultrasound screening, combined with maternal factors, best identifies risks for preterm birth, small for gestational age (SGA), and large for gestational age (LGA) babies. This approach significantly improves detection rates compared to second trimester screening alone.
Area of Science:
- Maternal-fetal medicine
- Diagnostic imaging in obstetrics
- Perinatal health outcomes
Background:
- Preterm birth, small for gestational age (SGA), and large for gestational age (LGA) are significant risk factors for neonatal and long-term health issues.
- Optimal timing for ultrasound screening to identify fetuses at risk for these adverse outcomes remains unclear.
- This study investigates the effectiveness of second and third trimester ultrasounds, alone and combined with maternal characteristics, for risk prediction.
Purpose of the Study:
- To determine the optimal period for ultrasound screening to detect fetuses at risk of preterm birth, SGA, or LGA.
- To evaluate the combined effectiveness of maternal characteristics and ultrasound measures (fetal weight, placental flow) in screening for adverse birth outcomes.
- To compare the performance of single versus combined trimester screening strategies.
Main Methods:
- A prospective, population-based cohort study involving 7677 pregnant women.
- Measurement of second and third trimester estimated fetal weight (EFW) and placental flow indices (uterine artery pulsatility, umbilical artery resistance).
- Screening performance assessed using receiver operating characteristic (ROC) curves and area under the curve (AUC), with sensitivity and specificity analysis.
Main Results:
- Maternal characteristics combined with second trimester EFW showed moderate screening performance.
- Adding third trimester EFW to maternal characteristics significantly improved AUC for preterm birth (0.64), SGA (0.79), and LGA (0.76).
- Incorporating third trimester placental measures further enhanced screening for preterm birth (AUC 0.72) and SGA (AUC 0.83), but combining second and third trimester data did not outperform third trimester results alone.
Conclusions:
- Combining third trimester ultrasound findings (fetal and placental measures) with maternal characteristics offers the best screening performance for preterm birth, SGA, and LGA risks.
- Third trimester screening demonstrates a potential to double the detection rate of fetuses at risk for common adverse birth outcomes compared to second trimester screening.
Background:
Preterm birth, small size for gestational age (SGA) and large size for gestational age (LGA) at birth are major risk factors for neonatal and long-term morbidity and mortality. It is unclear which periods of pregnancy are optimal for ultrasound screening to identify fetuses at risk of preterm birth, SGA or LGA at birth. We aimed to examine whether single or combined second and third trimester ultrasound in addition to maternal characteristics at the start of pregnancy are optimal to detect fetuses at risk for preterm birth, SGA and LGA.
Methods:
In a prospective population-based cohort among 7677 pregnant women, we measured second and third trimester estimated fetal weight (EFW), and uterine artery pulsatility and umbilical artery resistance indices as placenta flow measures. Screen positive was considered as EFW or placenta flow measure < 10th or > 90th percentile. Information about maternal age, body mass index, ethnicity, parity, smoking, fetal sex and birth outcomes was available from questionnaires and medical records. Screening performance was assessed via receiver operating characteristic (ROC) curves and area under the curve (AUC) along with sensitivity at different false-positive rates.
Results:
Maternal characteristics only and in combination with second trimester EFW had a moderate performance for screening for each adverse birth outcome. Screening performance improved by adding third trimester EFW to the maternal characteristics (AUCs for preterm birth 0.64 (95%CI 0.61 to 0.67); SGA 0.79 (95%CI 0.78 to 0.81); LGA 0.76 (95%CI 0.75; 0.78)). Adding third trimester placenta measures to this model improved only screening for risk of preterm birth (AUC 0.72 (95%CI 0.66 to 0.77) with sensitivity 37% at specificity 90%) and SGA (AUC 0.83 (95%CI 0.81 to 0.86) with sensitivity 55% at specificity 90%). Combining second and third trimester fetal and placental ultrasound did not lead to a better performance as compared to using only third trimester results.
Conclusions:
Combining single third trimester fetal and placental ultrasound results with maternal characteristics has the best screening performance for risks of preterm birth, SGA and LGA. As compared to second trimester screening, third trimester screening may double the detection of fetuses at risk of common adverse birth outcomes.
