Relationship between body mass index and preterm delivery before and during pregnancy

Background: Preterm delivery is the birth of an infant before 37 gestational weeks. In prior studies, relationship between body mass index (BMI) and preterm delivery before pregnancy and weight again during pregnancy has been inconsistently reported. This study was done to determine the association of the above two factors with preterm labor. Materials and Method: This research was done on 502 pregnant women age range between 18-35 years and gestational age between 14-18 weeks of pregnancy. Gestational age determined by last menstrual period (LMP) and ultrasound imaging of the first trimester pregnancy. BMI was measured based on pre-pregnancy weight. The medical history and midwifery questionnaires, completed and their weight gain during pregnancy and the occurrence of preterm delivery were studied. Participants in the study, divided into three groups based on pre-pregnancy BMI and three other groups based on weight again during pregnancy; then each group of BMI divided into three subgroups based on pregnancy weight. Results: In this study, the incidence of preterm labor in women with higher and lower BMI was higher than pregnant women with normal BM (p=0.002). Statistical analysis did not show any statistical significant difference between weight again during pregnancy and preterm delivery (p=0.82). Survey of both pre-pregnancy BMI and weight again during was apparently significant (p=0.04) but it was only due to the effect of BMI. Conclusion: This study showed that there is an association between abnormal BMI and preterm deliver. Therefore, education programs and consultation with a specialist in nutrition are suggested for women in reproductive aged.