The Association between Maternal Demographic Factors and Birth Weight

Background: Fetal weight at birth is of paramount importance to the obstetrician and neonatologist; it’s a key factor in management decisions. The major determinants of birth weight are obstetrics, genetic, and maternal demographic factors.

Objective: The objective of this study is to determine the influence of maternal demographic factors on birth weight. Specifically, it would determine the effects of body mass index, parity, tribe, maternal age, gestational age at delivery, educational level, height and occupation on birth weight.

Materials and Methods: It was an observational cross-sectional study of 1620 booked pregnant women who delivered at the Niger Delta University Teaching Hospital. Their case notes were retrieved and relevant information such parity, educational level, maternal age, tribe, and occupation was obtained. Others were maternal height and weight at booking, gestational age at delivery, and birth weight. Body mass index (BMI) was calculated from height and weight and categorized. Data was analyzed with Chi square, Pearson’s correlation coefficient, simple linear regression, and multivariate analysis

Results: The mean birth weight was 3.11 ± 0.5kg, and a great majority of the babies (88.7%) were of normal birth weight; the prevalence of low birth weight (LBW) and fetal macrosomia were 6.8% and 4.1% respectively. Fetal macrosomia was associated with advanced maternal age (> 40 years), X2= 32.32, p = 0.0001, employment, Odds ratio = 3.15(1.03. 9.62), and obesity class 1 and 11, p = 0.004, and p = 0.003 respectively. LBW was significantly associated with underweight women, Odds ratio = 7.63(3, 09. 18, 88), and delivery of very low birth weight (VLBW) babies was higher among women from Igbo tribe, Odds ratio = 4.64 (1.85, 11.56).

Using multivariate analysis, maternal demographic factors could only explain 19.6% of the factors responsible for birth; the most important predictors were gestational age at delivery, maternal height, educational level and BMI.

Conclusion: Though maternal demographic factors significantly affects birth weight, the bulk of the determinants (80.4%) are outside these factors, and it could be from genetic, obstetrics or environmental factors.