Relationships between pregnancy outcomes, biochemical markers and pre-pregnancy body mass index

Objective: We examined the relationships between pre-pregnancy maternal body mass index (BMI), pregnancy outcomes and biochemical markers. Design: This study was conducted as a cross-sectional analysis. Subjects: Korean women in their second and third trimesters of pregnancy were recruited at two hospitals in the metropolitan Seoul area. Pre-pregnancy BMI was categorized in four groups according to the Asia-Pacific standard. Measurements: Fasting blood samples were obtained and analyzed for serum levels of homocysteine, folate and high-sensitivity C-reactive protein (hs-CRP). Concentrations of fetal fibronectin were assessed in the cervix and vagina, and cervical length was measured. Results: Obese subjects had a lower education level and a lower income level than subjects of normal weight. The level of maternal stress was positively associated with pre-pregnancy BMI. Normal weight subjects were more likely to eat breakfast and consume meals of appropriate size than the rest of our sample. In overweight and obese subjects, weight gain during pregnancy was significantly lower than in the underweight and normal subjects. High pre-pregnancy maternal BMI increased the risks of preterm delivery (odds ratio (OR) = 2.85, confidence interval (CI) = 1.20-6.74), low-birth-weight (LBW) infants (overweight subjects: OR = 5.07, CI = 1.76-14.63; obese subjects: OR = 4.49, CI = 1.54-13.13) and macrosomia. In obese subjects, the average serum folate level was significantly lower than in the underweight subjects. In obese subjects, the average serum hs-CRP level was significantly higher than in the rest of our sample. Conclusion: Pregnancy outcomes are influenced by pre-pregnancy BMI. These findings suggest that women can minimize their risks of preterm delivery, LBW and macrosomia by maintaining normal pre-pregnancy BMI. International Journal of Obesity (2011) 35, 570-577; doi: 10.1038/ijo.2010.162; published online 31 August 2010