Pregnancy Weight Gain Calculator

Healthy weight gain depends on your pre-pregnancy BMI. The Institute of Medicine recommends: 28-40 lbs for underweight women (BMI <18.5), 25-35 lbs for normal weight (BMI 18.5-24.9), 15-25 lbs for overweight (BMI 25-29.9), and 11-20 lbs for obese women (BMI ≥30). These ranges help optimize both maternal and infant health outcomes.

Multiple pregnancies require higher weight gain. For twins, the IOM recommends: 37-54 lbs for normal weight women, 31-50 lbs for overweight, and 25-42 lbs for obese women. Twin pregnancies typically require 40-56% more weight gain than singleton pregnancies to support healthy fetal development.

Weight gain follows a specific pattern: minimal gain in the first trimester (0.5-5 lbs), steady gain in the second trimester (~1 lb/week), and gradual increase in the third trimester (0.5-1 lb/week). About 35% goes to fetal components (baby, placenta, amniotic fluid) and 65% to maternal changes (breast tissue, uterus, blood volume, fat stores).

Inadequate weight gain increases risks of intrauterine growth restriction (1.7-2.6x higher risk), preterm delivery (28% increase), and breastfeeding difficulties. Excessive weight gain raises risks of gestational diabetes (15-45% increase), cesarean delivery (20-30% higher rates), and long-term obesity for both mother and child.

Consult your healthcare provider if you experience sudden weight gain (>3 lbs in one week), no weight gain for several weeks in the second/third trimester, or if your total gain significantly exceeds or falls below IOM recommendations. Regular prenatal visits help monitor healthy weight progression.