From the Guidelines
Screening for fetal presentation should be performed routinely at 36 weeks gestation for all pregnant women, using abdominal palpation with Leopold's maneuvers, and confirmed with ultrasound if necessary, as recommended by the most recent and highest quality study 1. This assessment is crucial for identifying non-cephalic presentations, particularly breech, which can lead to complications during labor and delivery if left undiagnosed.
- The optimal method for screening fetal presentation in the third trimester involves a combination of physical examination and ultrasound, as outlined in the ACR Appropriateness Criteria for second and third trimester screening for fetal anomaly 1.
- The use of ultrasound in the third trimester has been shown to have utility for perinatal management and postnatal follow-up, with 15% of all anomalies found only in the third trimester 1.
- Early detection of fetal malpresentation allows for timely intervention, such as external cephalic version (ECV), which can reduce the risk of complications during labor and delivery 1.
- The American College of Radiology recommends that at least one ultrasound be offered routinely to all pregnant women between 18 and 20 weeks of gestation, and selectively in the third trimester as needed 1.
- A study by Bricker et al found no evidence of improved antenatal, obstetric, or neonatal outcome or morbidity in those screened in the third trimester versus controls, but this study did not specifically address the issue of fetal presentation 1.
- In contrast, a study by Manegold et al showed that third trimester ultrasound had utility for perinatal management and postnatal follow-up, highlighting the importance of screening for fetal presentation in the third trimester 1.
From the Research
Optimal Method for Screening Fetal Presentation
The optimal method for screening fetal presentation in the third trimester involves universal late-pregnancy ultrasonography.
- A study published in 2019 2 found that universal ultrasound scanning for breech presentation near term (36 weeks of gestational age) in nulliparous women was cost-effective and could virtually eliminate undiagnosed breech presentation.
- Another study from 2015 3 compared the utility of routine third-trimester ultrasound examination at 36 weeks' gestation with that at 32 weeks in detecting fetal growth restriction (FGR) and found that screening at 36 weeks was more effective.
Detection Rates and Cost-Effectiveness
- The 2019 study 2 found that universal late-pregnancy ultrasound would identify around 14,826 otherwise undiagnosed breech presentations across England annually and would be cost-effective if fetal presentation could be assessed for £19.80 or less per woman.
- A 2015 study 4 found that universal third-trimester fetal biometry roughly tripled detection of small-for-gestational-age (SGA) infants and that combined analysis of fetal biometry and fetal growth velocity identified a subset of SGA fetuses that were at increased risk of neonatal morbidity.
Timing of Screening
- A study from 2015 5 investigated the value of fetal biometry at 19-24 weeks' gestation in predicting delivery of SGA neonates and found that prenatal prediction of a high proportion of SGA neonates necessitates the undertaking of screening in the third trimester of pregnancy.
- The study suggested that the timing of such screening, either at 32 and/or 36 weeks, should be contingent on the results of the assessment at 19-24 weeks.
- Another study from 2019 6 found that routine ultrasound examination at 36 weeks' gestation was more effective than that at 32 weeks in predicting birth of SGA neonates.