THE RELATIONSHIP BETWEEN BODY MASS INDEX IN EARLY PREGNANCY AND GESTATIONAL WEIGHT GAIN IN PREGNANT WOMEN WITH NEONATAL BIRTH WEIGHT

Abstract

The body mass index (BMI) of a pregnant woman plays a significant role in the outcome of pregnancy and the birth weight of the newborn (BW). A similar impact has also been observed in cases of excessive gestational weight gain (GWG) in pregnant women. Therefore, assessing the nutritional status of the mother is important not only because it identifies women at gestational risk but also due to its role in predicting the health condition of the newborn.
Objectives: The aim of this study was to investigate the association between the mother's body mass index in early pregnancy and gestational weight gain on the birth weight of the newborn.
Methods: We conducted a cross-sectional study at the Department of Obstetrics and Gynecology at the Health Center Cazin in Bosnia and Herzegovina, from 2024 to 2025. We analyzed 228 pregnant women with recorded values of BMI, GWG, and birth weight (PTN) in the pregnancy and birth database. BMI classification was based on the WHO cutoff points: Underweight: BMI <18.5 kg/m², Normal weight: BMI 18.5-24.9 kg/m², Overweight: BMI 25-29.9 kg/m², and Obese: BMI >30 kg/m². GWG was classified into three categories: below, within, or above the recommended limits, and the values were compared with the 2009 IOM guidelines for each BMI category. Women with GWG within the recommended range according to IOM were categorized as having normal GWG, while those who gained less or more than the recommended limits were categorized as having insufficient or excessive GWG. Birth weight (PTN) values were obtained from the pregnancy and birth database. Statistical analysis was performed using IBM SPSS, version 27. Data were analyzed using descriptive statistics, including frequencies, mean values, and standard deviations (SD). The statistical model used was one-way univariate analysis of variance.
Results and Discussion: In our sample, 4.4% of pregnant women were malnourished at the beginning of pregnancy and gave birth to babies with lower birth weight (3047±416 g), while 75.9% had normal body weight with higher birth weight values (3417±412 g). 18.9% of the pregnant women were in the overweight category with a higher birth weight (3557±470 g) compared to those with normal body weight, and 0.9% were obese, class I, with the highest birth weight (3575±459 g). The average birth weight was 3429±432 g. Among women with a normal BMI, macrosomia was present in 4.8%, while in the overweight category, it was 3.5%. The average body weight of pregnant women at the beginning of pregnancy was 61.8±8.9 kg, while before delivery it was 73.1±9.5 kg. The total gestational weight gain (GWG) for all pregnant women was 11.1±4.6 kg. The rate of babies born with lower birth weight was 1.3%, while the rate of babies born with macrosomia was 8.3%. A moderate positive correlation was found between BMI at the beginning of pregnancy and birth weight (r=0.159 *p=0.016), and between GWG and birth weight (r=0.207 **p=0.002). Lower birth weight was found exclusively in pregnant women who gained less than the recommended IOM GWG.
Conclusion: BMI in early pregnancy significantly influenced newborn birth weight, both in the underweight women category and in the category of women with excessive BMI. Negative outcomes in newborns, such as lower birth weight and macrosomia, were significantly present in women who gained weight below or above the IOM recommendations.
Recommendations: Nutritional counseling for women is essential to achieve optimal and reduce excess body weight before conception, as well as to monitor weight gain during pregnancy, in order to avoid negative impacts on fetal and maternal health.