Gestational weight gain guidelines
The Institute of Medicine (IOM) 2009 guidelines remain the most widely used reference for gestational weight gain recommendations. They're stratified by pre-pregnancy BMI because baseline body composition affects how much additional weight is optimal for a healthy pregnancy outcome.
Weight gain in pregnancy isn't just fat. It includes the baby (~3.3 kg), placenta (~0.7 kg), amniotic fluid (~0.8 kg), uterine growth (~0.9 kg), increased blood volume (~1.4 kg), breast tissue (~0.4 kg), and fluid retention (~1.5 kg). That's about 9 kg for the non-fat components alone in a typical singleton pregnancy.
Risks of inadequate and excessive gain
Too little weight gain is associated with small-for-gestational-age babies, preterm birth, and impaired fetal brain development. Too much is associated with gestational diabetes, hypertensive disorders, large-for-gestational-age babies, caesarean delivery, and retained postpartum weight. The sweet spot varies by starting BMI.
Twin pregnancies
IOM 2009 recommendations for twin pregnancies are less robust due to limited data. The guidelines suggest 17-25 kg for normal BMI, 14-23 kg for overweight, and 11-19 kg for obese women carrying twins. No specific recommendation exists for underweight women with twins.
Related tools
For due date and gestational age tracking, see Due Date Calculator. For standard BMI classification, see BMI Calculator. For ovulation and cycle tracking, see Ovulation Calculator. For APGAR score at delivery, see APGAR Score.
References
- Institute of Medicine and National Research Council. Weight Gain During Pregnancy: Reexamining the Guidelines. Washington DC: National Academies Press; 2009.
- ACOG Committee Opinion No. 548. "Weight gain during pregnancy." Obstet Gynecol. 2013;121(1):210-212.