Risk factors for delivering a small for gestational age infant

Abstract

OBJECTIVE: To determine the risk factors for delivering a small for gestatJonal age (SGA) infant. METHODOLOGY: A prospective study was carried out at two MOH areas in the Gampaha district, during the period of May 2001 to April 2002. Eight hundred and twenty pregnant mothers were recruited at £16 weeks of gestation and followed up until partus. Demographic, socloeconomic and obstetric data of the mothers were gathered at the time of recruitment. Trimester specific exposure statuses along with potential confounding factors were gathered on average at the 12 , 28 and 36 weeks of gestation. Physical activities were assessed by asking the duration of specific postures adopted per day by the mothers during each trimester at home for house wives and both at home and during working hours for those who were engaged in paid employment. Shift work and work related physical and chemical exposures were also assessed. Psychosocial stress was ascertained using the Modified Life Events Inventory and the General Health QuestionnaireJJO. Ultrasound scan was performed to determine the gestationai age based on foetal biparietal diameter. SGA was assessed using customized growth centile charts developed by Gardosi et al. Univariate and multivariate logistic regression analysis (sample size=504) were applied and the results are expressed in odds ratios (OR) and 95% confidence intervals (95%CI) with the probability levels (P). RESULTS: When cut off for SGA was considered as <10 centile of the customized birth weight centiles, the proportion of SGA was 16.4%. Although the univariate analysis revealed that sleeping for < 8 hours during 2" or 3 or both trimesters (OR=1.645 95% CI= 1.00-2.67; P=0.04) and work related exposures during 2 or 3 or both trimesters (OR=2.42,95% GUI.19-4.93; P=0.01) were significantly associated with SGA, none of these factors became significant on multivariate logistic regression analysis. When the cut off was considered as <5 centile of the customised birth weight centiles, the proportion of SGA was 8.8%. Sleeping <8 hours during 2 or 3 or both trimesters (OR=2.34,95% CI=1.18-4.61; P=0.01), work related exposures during 2" or 3' or both trimesters (OR=2.91, 95% CM.27-6.65; P=0.01) and alcohol consumption during the 3' trimester {OR=4.33, 95% CI=1.11-16.94; P=0.03) had statistically significant association with SGA in the univariate analysis. Multivariate logistic regression also revealed that sleeping for <8 hours during 2" or 3 or both trimesters (OR=2.14, 95% 01=1.06-4.32; P=0.03), and walking for < 2.5 hours per day (OR=2.40> 95% CM.05-5-51; P=0.04) and alcohol consumption during the 3' trimester (OR=8.01,95% CM.31-49.02; P=0.02) were risk factors. CONCLUSIONS: Risk factors for being SGA when SGA is defined as <5 centile of the customised birth weight centiles are, sleeping for <8 hours during 2 or 3 or both trimesters, walking < 2.5 hours per day and alcohol consumption during 3 trimester. It is recommended that the importance of sleeping >8 hours and walking > 2.5 hours per day and avoidance of alcohol be emphasised to pregnant mothers.