Effect of Birth Weight and Early Pregnancy BMI on Risk for Pregnancy Complications

Objective: This study investigated the influence of birth weight on the risk of pregnancy complications, including preeclampsia (PE), gestational hypertension (GH), small for gestational age (SGA) pregnancy, spontaneous preterm birth, and gestational diabetes mellitus (GDM), and assessed the effect of early pregnancy BMI on this relationship. Methods: A total of 5,336 nulliparous women from the SCreening fOr Pregnancy Endpoints (SCOPE) study were included. Women’s birth weights were self-reported and confirmed via medical records when possible. A birth weight of 3,000 to 3,499 g was considered the reference. Results: After adjusting for confounders, birth weight < 2,500 g was associated with increased risk of GH (adjusted odds ratio [aOR] = 2.2, 95% CI = 1.3-3.7), PE (aOR = 1.7, 95% CI = 1.0-2.9), small for gestational age (aOR = 1.9, 95% CI = 1.1-3.2), and GDM (aOR = 2.4, 95% CI = 1.0-5.8) compared with the referent. Women born with birth weight < 2,500 g and who subsequently developed overweight or were diagnosed with obesity were at increased risk of GH (aOR = 2.2, 95% CI = 1.1-4.5), PE (aOR = 2.3, 95% CI = 1.2-4.5), and GDM (aOR = 3.2, 95% CI = 1.1-9.5) compared with women with birth weight ≥ 2,500 g and remained lean. Conclusions: Women who were born with a low birth weight are at increased risk of pregnancy complications. Those born small may have undergone “programming” in response to unfavorable intrauterine conditions. In such women, the physiological demands of pregnancy may act as a “second hit,” leading to pregnancy complications.