Birthweight Percentiles by Gestational Age and Maternal Factors that affect Birthweight In Singapore

Abstract

ABSTRACT

A. Introduction

Gestational age-specific birthweight growth curve is an essential tool for neonatal studies. Birthweight provides valuable information to both obstetricians and paediatricians on the intrauterine growth of neonates. It also provides a snapshot of the regional population distribution for the monitoring of epidemiological outcomes and public health care policies. B. Objectives

The aim of this study is to develop a gestational age-specific birthweight growth curves and percentile charts for infants in Singapore relevant to its three major ethnic groups - Chinese, Malay and Indian. We intend to identify factors which might influence birth weight such as maternal age, parity, antenatal disease, Assisted Reproductive Techniques (ART) pregnancies as well as infant gender and ethnicity. C. Materials and Methods

Data was collected and analyzed from maternity records of 21,656 infants born at the National University Hospital (NUH), Singapore, from 2000 - 2008. Descriptive statistics were used to examine the birthweight distributions and determine the mean and percentile distribution for each gestational age with respect to ethnicity. The effect of gestational age was illustrated by smoothed birthweight growth curve in weeks of gestation using quantile regression. Male and female birthweight growth curves were graphically overlaid to better illustrate observed differences, and selected points on the curves were compared and quantified in the corresponding tables. In order to study the effect of ethnicity, birthweight growth curves were also graphically overlaid for further analysis. The mean birthweight were also calculated by gestational age and ethnic groups. Analysis of variance (ANOVA) was performed to search for statistical significance between groups. Linear Regression was used to evaluate the trends over time for the period of 8 years. Mixed Model analysis was used to analyze the independent effects of gender, ethnic group, maternal age, parity, gestational age, ART pregnancy and various maternal diseases (gestational diabetes, anemia and hypertension) on birth weight.

D. Results Two versions of gestational age-specific birthweight growth curves and percentile charts were developed. The first version presents growth curves and percentiles chart for birthweights with gestational ages from 26 ? 41 weeks, consolidated for both genders. A second version for a more specific gestational window of 34 ? 41 weeks presents birthweight growth curves and percentiles chart, now segregated by both gender and ethnicity. Chinese babies were found to be at least 53.2g heavier than the Indians (P < 0.001) and 38.3g heavier than the Malays (P < 0.001). However, no significant differences were observed in the birthweight between the Malays and Indians. Significant prediction for smaller babies was found in mothers under the age of 20, primigravidas and women who conceived via ART or developed gestational hypertension.

E. Discussion

The establishment of updated gestational age-specific birthweight growth curves and percentile charts suited for the local clinical profile allows both obstetricians and paediatricians to better assess neonatal health. Maternal factors like age, parity and maternal diseases as well as ethnicity all affect birth weight. These findings are a useful reference for future research that will help to improve perinatal health.