Customised growth charts in large-for-gestational-age infants and the association with emergency caesarean section rate.

BACKGROUND AND AIM: Large-for-gestational-age (LGA) infants are at increased risk of intrapartum complications. However, some infants classified as LGA may be appropriate-for-gestational-age (AGA) if adjusted for maternal stature. We determined whether customisation of birthweight centiles by maternal height, or height and weight, improves the detection of LGA infants at risk of complications. METHODS: We conducted a retrospective analysis of 38 246 term, singleton nulliparous women. We compared population birthweight centiles to those customised by height, or height and weight for complications including intrapartum caesarean section, instrumental delivery, postpartum haemorrhage, anal sphincter injury and neonatal outcomes. RESULTS: Those considered LGA when customised for height but AGA by population centiles (LGA-ht-only) were at increased risk of intrapartum emergency caesarean section compared with infants AGA on all charts (AGA-all); odds ratio (OR) 4.64, 95% CI 3.22-6.76. In contrast, infants considered LGA on population charts, but AGA when customised by height (LGA-pop-only) were not at increased risk compared to the AGA-all group (OR 1.43, 95% CI 0.70-1.88). Infants classified as LGA-ht-only compared to LGA-pop-only remained at significantly higher risk after adjustment for potential confounders (aOR 3.27; 95% CI 2.02-5.31). No difference was seen for any other outcomes. No benefit was seen with customisation by both maternal height and weight. CONCLUSION: Women with an infant classified as AGA on population centiles but LGA when customised for height are at increased risk of intrapartum caesarean section. This is a population unrecognised in current practice. Fetal growth should be customised for maternal height when making assessments regarding the LGA infant.

Why we miss fetal growth restriction: Identification of risk factors for severely growth-restricted fetuses remaining undelivered by 40 weeks gestation.

BACKGROUND: Severe fetal growth restriction (FGR) is a leading cause of adverse perinatal morbidity and mortality; however, in Victoria, 35% of severely growth-restricted infants are undelivered by 40 weeks gestation. AIMS: We aimed to identify factors associated with failure to deliver severely growth-restricted fetuses by 40 weeks gestation. METHODS: We conducted a retrospective case-control study of term singletons born <3rd centile for gestation at a single tertiary centre (2010-2017). Infants with a planned delivery for FGR between 37.0-39.6  weeks gestation ('planned birth' group; n = 187) were compared with those undelivered by 40.0  weeks ('undelivered' group; n = 233). Variables assessed included the presence of risk factors for FGR, model of care, symphyseal-fundal height measurements and third trimester ultrasounds. RESULTS: An equivalent proportion of women were 'high-risk' for FGR on history (31.3% vs 38.0%, P = 0.187) in the planned and undelivered groups. Women booked under low-risk models (shared care and midwifery-led care) were significantly more likely to be in the undelivered group compared to those booked under traditional collaborative models (79.8% vs 37.4%, P < 0.001). Women in the undelivered group were less likely to have received a third trimester ultrasound (93.0% vs 40.3%, P < 0.001); however, they were more likely to have had a reassuring ultrasound with an estimation of fetal weight or abdominal circumference >10th centile (78.7% vs 16.1%, P < 0.001). CONCLUSIONS: Failure to deliver the severely growth-restricted fetus before 40.0 weeks is more likely to occur in the following situations: (i) failure to receive an indicated third trimester ultrasound; (ii) the presence of falsely reassuring third trimester ultrasound scan; and (iii) booking under a low-risk rather than traditional collaborative models of care.