The Relationship between Maternal Body Mass Index at the Beginning of Pregnancy and Infants' Birth Weight and Pregnancy Outcomes

Document Type : Original Article

Authors

1 Associate Professor , Department of Biostatistics, Health Sciences Research Center, School of Health, Mashhad University of Medical Sciences, Mashhad, Iran.

2 Assistant Professor, Department of Neonatology, School of Medicine, Mashhad University of Medical Science, Mashhad, Iran.

3 Associate Professor, Department of Reproductive Health, School of Nursing and Midwifery, Mashhad University of Medical Sciences, Mashhad, Iran.

4 Assistant Professor, Department of Obstetrics and Gynecology, Ovulation Dysfunction Research Center, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

5 Ph.D. Student of Reproductive Health, Student Research Committee, School of Nursing and Midwifery, Mashhad University of Medical Science, Mashhad, Iran.

6 General Practitioner, School of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.

Abstract

Introduction: Birth weight is one of the main indices of growth and one of the determining factors of survival. The purpose of this study was determining the relationship between maternal body mass index at the beginning of pregnancy and infants' birth weight and pregnancy outcomes.
Methods: This cross-sectional study was conducted on 800 pregnant women with gestational age less than 12 weeks who referred to health centers of Mashhad, Iran in 2010. In the first prenatal medical appointment, a questionnaire containing personal information was completed and mothers' body mass index was calculated. At birth, the infants' weights and other variables were surveyed. Data were analyzed using SPSS software (version 16) and chi-square, student t-test, Pearson correlation and generalized linear models. P value less than 0.05 was considered significant.
Results: Mean birth weight of infants had increased with the increase in their mother's weight (p<0.001). Also, mean of infants' birth weight was significantly higher in mothers aged 35 or more (p=0.03), multiparas (p=0.001) and mothers who gave birth to male infants (p<0.0001). Low birth weight and preterm labor were significantly more prevalent among underweight mothers (p<0.0001). Macrosomia was seen more among obese mothers. Furthermore, the incidence of cesarean section increased with the increase in mothers' body mass index. Mothers' body mass index at the beginning of pregnancy has a role in predicting the infants' birth weight.
Conclusion: Abnormal body mass index leads to undesirable prenatal complications. As a result, body mass index can be used to identify pregnant women who are at the risk of maternal and infantile complications and take the necessary measure to prevent them.

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