Correlation Between Maternal Body Mass Index, Non-stress Test Parameters and Pregnancy Outcomes in Nulliparous Women

Abstract

<strong>Background:</strong> An increase in maternal body mass index (BMI) before pregnancy can cause overweight during pregnancy, and negatively affect both the mother and the fetus. Non-stress test (NST) is the most common way to evaluate the fetus during pregnancy. <strong>Objectives:</strong> This study aimed to evaluate the correlation between maternal BMI and NST parameters as well as the pregnancy outcomes in nulliparous women. <strong>Materials and Methods:</strong> This case-control study, comprised 67 nulliparous women with the gestational age of 24-28 weeks, selected by simple random sampling, who were admitted to Shooshtari and Hafez hospitals from 2011 to 2012. The case group included 35 pregnant women with BMI greater than 26. The control group consisted of 32 pregnant women with BMI lower than 26. NST was applied to groups and evaluated reactive and non-reactive parameters, basal fetal heart rate, and number of accelerations. Chi-square test was used to examine the reactive and non-reactive parameters and type of delivery. Other variables were statistically analyzed using 1-way analysis of variance (ANOVA). <strong>Results:</strong> Our results indicated that the frequency of NST reactive and non-reactive parameters was 41%, 59% in the case group, respectively and 55%, 45% in the control group, respectively. Besides, a significant difference was found between the case and the control group regarding reactive parameters (P = 0.02). However, no significant difference was observed between the two groups concerning the mean of basal fetal heart rate ( P= 0.3). However, the number of accelerations in the case group was significantly lower than that of the control group ( P= 0.001). Significant increases were found in the case group regarding the mean of post-delivery weight ( P= 0.02), BMI after delivery ( P= 0.005), neonatal birth weight ( P= 0.001), gestational age ( P= 0.001), and caesarian section (CS) delivery ( P= 0.01). <strong>Conclusions:</strong> This study revealed that the increase in maternal BMI was accompanied by a decrease in non-reactive parameters of NST and the number of accelerations of the fetal heart rate which is the most important index for fetal health. Also, a significant increase was observed regarding maternal BMI one month after delivery, neonatal birth weight, gestational age, and CS delivery.