A test of agreement of customised birthweight models.

BACKGROUND: The objective of this study was to determine whether the physiological effects on birthweight as described by customised birthweight models (CBMs) from various populations and locations are consistent when applied to a single sample. METHODS: The predicted birthweight was calculated for 52 826 White-European singleton term births between 1997 and 2008 from a large Australian hospital using the same set of variables from 12 published CBMs. The accuracy of prediction was tested against both the actual birthweight and a reference model. Intraclass correlation coefficients (ICCs) along with 95% confidence intervals of the measurements, paired differences (predicted-actual birthweight) and absolute values of the paired differences are reported. RESULTS: The average difference in predicted and actual birthweight was <200 g for all CBMs, with ICCs for all but one model indicating fair agreement (between 0.3 and 0.5). When compared with the reference model, eight of the 11 models had a difference in predicted birthweight of <220 g, and the ICCs indicated that the majority of models had strong agreement. CONCLUSION: All published CBMs demonstrated ability to predict birthweight with reasonable accuracy. The effects of maternal and fetal characteristics on birthweight appear to be consistent across birthweight models. This finding is a further step in validating the CBM, and provides greater evidence for the creation of a global model.

Customised birthweight models: do they increase identification of at-risk infants?

AIM: The study aims to describe the cohort of women and babies who are classified as small-for-gestational age (SGA) at term by both an Australian customised birthweight model (CBM) and a commonly used population-based standard, and to investigate and compare the utility of these models in identifying babies at risk of experiencing adverse outcomes METHODS: Routinely collected data on 54 890 singleton-term births at the Mater Mothers' Hospitals, Brisbane, with birthweight less than 4000 g between January 1997 and December 2008, was extracted. Each birth was classified as SGA (<10th centile) or not SGA by either and/or both methods: population-based standards (SGApop ) and CBM (SGAcust ). Babies classified as SGApop , SGAcust or SGAboth were compared with those not classified as SGA by both methods using relative risk and 95% confidence interval, and those only classified as SGAcust were compared with those only classified as SGApop . Maternal demographics, maternal risk factors for fetal growth restriction, pregnancy and labour complications and adverse neonatal outcomes are reported. RESULTS: A total of 4768 (8.7%) births were classified as SGApop , while 6479 (11.8%) were SGAcust of whom 4138 (63.9%) were also classified as SGApop . Maternal risk factors such as smoking and hypertension were statistically higher for the SGAcust group when compared with SGApop . For the majority of adverse neonatal outcomes, a trend was noted to increased identification using the CBM. CONCLUSION: The CBM provides a modest improvement when compared to a population-based standard to identity term infants at birth who are at risk of adverse neonatal outcomes.

A survey of policies for the monitoring of fetal growth in Australian and New Zealand hospitals.

BACKGROUND: Fetal growth restriction is associated with increased perinatal mortality and morbidity and adverse developmental outcome. However, evidence is lacking on optimal approaches to antenatal screening of fetal size and growth. AIMS: To determine the current policies and practices for assessment of fetal size and monitoring fetal growth with a view to informing future research in this area. METHODS: Web-based survey of Directors of Obstetrics and Gynaecology in maternity hospitals with over 1000 births per annum in Australia and New Zealand (ANZ). The survey focussed on the existence and details of guidelines for the clinical assessment of fetal size and growth in low- and high-risk pregnancies, techniques utilised for clinical assessment of fetal size and growth and the use of birthweight charts. RESULTS: Completed surveys were received from 49 (66%) of the 74 hospitals surveyed. Forty-four percent of hospitals have a fetal growth screening guideline, with abdominal palpation and symphysis fundal height (SFH) measurement the most common screening tools. Seventy-nine percent indicated that obstetric or birthweight charts were in use; 39% were unsure which chart/s were in use, and use differed by region. There was reasonable agreement regarding decision to take action following discrepancies between gestational age and SFH. Sixty-five percent of participants are interested in participating in a randomised controlled trial in this area. CONCLUSIONS: The survey revealed that while there is some agreement with respect to methods used in the clinical assessment of fetal size and growth, there is interest in ANZ hospitals to pursue this area of research further.