The test accuracy of antenatal ultrasound definitions of fetal macrosomia to predict birth injury: A systematic review

Abstract

To determine which ultrasound measurement for predicted fetal macrosomia most accurately predicts adverse delivery and neonatal outcomes. Study DesignFour biomedical databases searched for studies published after 1966.Randomised trials or observational studies of women with singleton pregnancies, resulting in a term birth who have undergone an index test of interest measured and recorded as predicted fetal macrosomia ≥28 weeks.Adverse outcomes of interest included shoulder dystocia, brachial plexus injury (BPI) and Caesarean section. ResultsTwenty-five observational studies (13,285 participants) were included. For BPI, the only significant positive association was found for Abdominal Circumference (AC) to Head Circumference (HC) difference > 50 mm (OR 7.2, 95% CI 1.8 to 29). Shoulder dystocia was significantly associated with abdominal diameter (AD) minus biparietal diameter (BPD) ≥ 2.6 cm (OR 4.2, 95% CI 2.3 to 7.5, PPV 11%) and AC > 90th centile (OR 2.3, 95% CI 1.3 to 4.0, PPV 8.6%) and an estimated fetal weight (EFW) > 4000 g (OR 2.1 95%CI 1.0 to 4.1, PPV 7.2%). ConclusionsEstimated fetal weight is the most widely used ultrasound marker to predict fetal macrosomia in the UK. This study suggests other markers have a higher positive predictive value for adverse outcomes associated with fetal macrosomia.

Accelerated fetal growth velocity across the third trimester is associated with increased shoulder dystocia risk among fetuses who are not large-for-gestational-age: A prospective observational cohort study

“…While assessment for macrosomia is applicable to nulliparous and parous women alike, this approach has several limitations. There is no universally accepted ultrasound definition of macrosomia; there are multiple different formulae available from which to calculate EFW and by which to assign EFW centile; ultrasound biometry measurements all have clinically significant error margins; and ultrasound quality and formulae are both less accurate when imaging larger babies [ 16 , 18 , 19 ]. A systematic review of the many different ultrasound definitions of macrosomia recently evaluated absolute measurement and centile cut-offs for AC and EFW as well as other fetal measurements for their prediction of shoulder dystocia.…”

“…A systematic review of the many different ultrasound definitions of macrosomia recently evaluated absolute measurement and centile cut-offs for AC and EFW as well as other fetal measurements for their prediction of shoulder dystocia. The best ultrasound predictor of shoulder dystocia was not EFW >95 th centile or >4000g, but was difference in abdominal and biparietal diameters of ≥2.6cm [ 18 ]. Definitions of macrosomia significantly associated with shoulder dystocia still failed to predict up to 60% of cases [ 18 ]–again highlighting that a large proportion of dystocias occur among non-macrosomic infants.…”

“…The best ultrasound predictor of shoulder dystocia was not EFW >95 th centile or >4000g, but was difference in abdominal and biparietal diameters of ≥2.6cm [ 18 ]. Definitions of macrosomia significantly associated with shoulder dystocia still failed to predict up to 60% of cases [ 18 ]–again highlighting that a large proportion of dystocias occur among non-macrosomic infants. We suggest that accelerated growth velocity–identifying pathological overgrowth–may be a useful adjunct to dichotomous thresholds of suspected macrosomia in identifying pregnancies at risk.…”

“…We suggest that accelerated growth velocity–identifying pathological overgrowth–may be a useful adjunct to dichotomous thresholds of suspected macrosomia in identifying pregnancies at risk. That the best current predictor of shoulder dystocia is a disproportionately large AC [ 18 ]–and that the AC is where accelerated fetal growth is most likely to manifest [ 20 ]–suggests that growth velocity, alone or in combination with other markers, has potential to improve predictive accuracy.…”

Establish a new equation for ultrasonographic estimated fetal weight in Chongqing: a prospective study

“…Prenatal ultrasound can accurately predict fetal weight, so as to timely detect giant infants, reduce unnecessary trial delivery, and avoid maternal and infant injuries such as cervical laceration, shoulder dystocia, bone and brachial plexus injury [19][20][21]. It can reduce the increase of selective cesarean section rate caused by incorrect EFW and insu cient con dence of pregnant women in trial delivery [22].…”