Abstract
SummaryBackgroundFetal growth restriction is a major determinant of adverse perinatal outcome. Screening procedures for fetal growth restriction need to identify small babies and then differentiate between those that are healthy and those that are pathologically small. We sought to determine the diagnostic effectiveness of universal ultrasonic fetal biometry in the third trimester as a screening test for small-for-gestational-age (SGA) infants, and whether the risk of morbidity associated with being small differed in the presence or absence of ultrasonic markers of fetal growth restriction.MethodsThe Pregnancy Outcome Prediction (POP) study was a prospective cohort study of nulliparous women with a viable singleton pregnancy at the time of the dating ultrasound scan. Women participating had clinically indicated ultrasonography in the third trimester as per routine clinical care and these results were reported as usual (selective ultrasonography). Additionally, all participants had research ultrasonography, including fetal biometry at 28 and 36 weeks' gestational age. These results were not made available to participants or treating clinicians (universal ultrasonography). We regarded SGA as a birthweight of less than the 10th percentile for gestational age and screen positive for SGA an ultrasonographic estimated fetal weight of less than the 10th percentile for gestational age. Markers of fetal growth restriction included biometric ratios, utero-placental Doppler, and fetal growth velocity. We assessed outcomes for consenting participants who attended research scans and had a livebirth at the Rosie Hospital (Cambridge, UK) after the 28 weeks' research scan.FindingsBetween Jan 14, 2008, and July 31, 2012, 4512 women provided written informed consent of whom 3977 (88%) were eligible for analysis. Sensitivity for detection of SGA infants was 20% (95% CI 15–24; 69 of 352 fetuses) for selective ultrasonography and 57% (51–62; 199 of 352 fetuses) for universal ultrasonography (relative sensitivity 2·9, 95% CI 2·4–3·5, p<0·0001). Of the 3977 fetuses, 562 (14·1%) were identified by universal ultrasonography with an estimated fetal weight of less than the 10th percentile and were at an increased risk of neonatal morbidity (relative risk [RR] 1·60, 95% CI 1·22–2·09, p=0·0012). However, estimated fetal weight of less than the 10th percentile was only associated with the risk of neonatal morbidity (pinteraction=0·005) if the fetal abdominal circumference growth velocity was in the lowest decile (RR 3·9, 95% CI 1·9–8·1, p=0·0001). 172 (4%) of 3977 pregnancies had both an estimated fetal weight of less than the 10th percentile and abdominal circumference growth velocity in the lowest decile, and had a relative risk of delivering an SGA infant with neonatal morbidity of 17·6 (9·2–34·0, p<0·0001).InterpretationScreening of nulliparous women with universal third trimester fetal biometry roughly tripled detection of SGA infants. Combined analysis of fetal biometry and fetal growth velocity identified a subset of SGA fetuses that were at increased risk of neonatal morbidity.FundingNational Institute for Health Research, Medical Research Council, Sands, and GE Healthcare.
Highlights
Of the 3977 fetuses, 562 (14·1%) were identified by universal ultrasonography with an estimated fetal weight of less than the 10th percentile and were at an increased risk of neonatal morbidity
The aims of this study were to compare the diagnostic effectiveness of universal ultrasound as a screening test for SGA compared with selective ultrasound and to establish which, if any, of a series of previously described ultrasonic markers of fetal growth restriction (FGR) identified those SGA fetuses at an increased risk of an adverse outcome
Screen positive fetuses with normal growth velocity were not at increased risk of neonatal morbidity, whereas an estimated fetal weight (EFW) of less than the 10th percentile was associated with an increase of 3·9 times of neonatal morbidity in infants in the lowest decile of abdominal circumference growth velocity. 172 (4·3%) fetuses had the combination of an ultrasonic diagnosis of SGA plus the lowest decile of abdominal circumference growth velocity from universal ultrasonography
Summary
Use of ultrasonography to identify small-for-gestationalage (SGA) infants is widespread in contemporary obstetric practice.[1,2] In the USA, UK, and many other countries women are not routinely scanned in late pregnancy, but are selected for third trimester ultrasonography on the basis of pre-pregnancy risk factors, development of obstetric complications, and serial measurement of symphyseal-fundal height.[2,3] This approach identifies a third of SGA infants or fewer,[4,5,6] and unidentified SGA is a common finding in perinatal deaths.[7,8] a meta-analysis[9] of nine trials assessing universal late pregnancy ultrasonography, including about 27 000 women, showed no beneficial effect, which led to the recommendation that it should not be offered routinely in the third trimester.[2,3] www.thelancet.com Vol 386 November 21, 2015Panel: Research in contextSystematic review Previously reported large-scale systematic reviews have addressed the ability of universal ultrasonography to result in improved clinical outcome. Reported Cochrane reviews have examined both conventional ultrasound and use of Doppler flow velocimetry of the uteroplacental circulation Neither of these methods has been shown to improve outcome. The National Institute for Health and Care Excellence (NICE) did a highly detailed review of the methods of screening women at low risk for fetal wellbeing for the 2008 Guideline on Antenatal Care. This guideline included both results of the Cochrane reviews of clinical effectiveness of universal ultrasound and results of the new meta-analyses of diagnostic effectiveness of screening for small-for-gestational-age (SGA) infants. Many observational studies reported that SGA infants are at increased risk of complications, methods used to screen for SGA have low sensitivity and specificity, and undiagnosed SGA is a common finding in perinatal deaths
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