Perinatal outcome in SGA births defined by customised versus population‐based birthweight standards

Abstract

Objective To determine whether customised birthweight standard improves the de®nition of small for gestational age and its association with adverse pregnancy outcomes such as stillbirth, neonatal death, or low Apgar score.Design Population based cohort study. Population Births in Sweden between 1992-95 (n 326,377).Methods Risks of stillbirth, neonatal death, and Apgar score under four at ®ve minutes were calculated for the lowest 10% birthweights according to population-based and customised standards, and were compared with the data from the group with birthweights over this limit. Population attributable risks for stillbirth using various birthweight centile cutoffs were calculated for the two standards. Outcome measures Odds ratios and 95% con®dence intervals for stillbirth, neonatal death and Apgar score under four at ®ve minutes, and population attributable risks for stillbirth at different birthweight centiles. Results Risks of stillbirth, neonatal death, and Apgar score under four at ®ve minutes and population attributable risks of stillbirth were consistently higher if`small for gestational age' was classi®ed by a customised rather than by the population-based birthweight standard. Compared with infants who were not small for gestational age by both standards, the odds ratio for stillbirth was 6.1 (95% CI 5.0-7.5) for small for gestational age by customised standard only, whereas it was 1.2 (95 % CI 0.8-1.9) for small for gestational age by population standard only. Conclusions Compared with the population-based birthweight standard, a customised birthweight standard increases identi®cation of fetuses at risk of stillbirth, neonatal death and Apgar score under 4 at 5 minutes, probably due to improved identi®cation of fetal growth restriction.

Customised birthweight percentiles: does adjusting for maternal characteristics matter?

“…11,[17][18][19] The increased RR of perinatal mortality among our study subjects classified as SGA by the customised standard was similar to results of previous studies of customised percentiles. 3,5 Unlike these earlier studies, however, we extended our evaluation of customised percentiles to additionally include a comparison with an intrauterine standard and found no statistically significant difference in the RR of stillbirth or early neonatal death between the customised and intrauterine standard. Conventional birthweight charts are biased at preterm gestational ages because of the association between fetal growth restriction and preterm birth, 11,[20][21][22][23][24] and our results demonstrate that correction of this bias through the use of an intrauterine Once this bias has been corrected, the process of customising for maternal characteristics does little to improve prediction of perinatal mortality.…”

“…Further details on the Swedish Medical Birth Register and the final study sample are provided elsewhere. 3,8 The study was approved by the McGill Faculty of Medicine Institutional Review Board.…”

“…By incorporating information generally believed to have a physiological influence on fetal growth (such as maternal height, pre-pregnancy body mass index [BMI], parity, ethnicity, and fetal sex), customised percentiles were designed to better differentiate between infants who are small because their in utero growth has been restricted and infants who are small but have reached their individual growth potential. 2 Customised birthweight percentiles have consistently been shown to be superior to conventional birthweight-for-gestational-age percentiles in predicting perinatal morbidity and mortality [3][4][5] and, as a result, have been recommended for clinical use by practice guidelines of the British Royal College of Obstetricians and Gynaecologists. 6 Before customised birthweight charts replace conventional weight-for-age charts in clinical practice, however, a better understanding of their properties is needed.…”

Magnetic resonance imaging‐estimated placental perfusion in fetal growth assessment

“…Intrauterine growth restriction (IUGR) is a major cause of perinatal mortality and morbidity1, 2, 3 and is associated with long‐term consequences, including impaired neurological development4 and increased risks of developing cardiovascular disease5 and metabolic syndrome6. There are no effective therapies to reverse IUGR, and antenatal management is aimed at determining the ideal time for delivery, sometimes very prematurely.…”

Management of subsequent pregnancy after an unexplained stillbirth

“…61 Because many normal fetuses will be constitutionally small, use of customized centile charts has been found to be a better predictor of fetal growth restriction and stillbirth, but there is no evidence yet that prospective use of such charts reduces the rate of perinatal death in a screened population. 62 As a screening tool, a measurement of fetal abdominal circumference within the normal range effectively excludes growth restriction, 63 whereas oligohydramnios is suggestive of growth restriction. 64 However, of greatest value is an umbilical artery Doppler study: screening of high-risk populations using this method is the only surveillance method associated with a trend toward improvement in perinatal mortality.…”