ACOG/IOM Weight Gain Guidelines
The American College of Obstetricians and Gynecologists (ACOG) and the Institute of Medicine (IOM) provide weight gain recommendations based on pre-pregnancy BMI:
| Pre-pregnancy BMI | Category | Recommended Gain |
|---|---|---|
| Below 18.5 | Underweight | 28-40 lbs (12.5-18 kg) |
| 18.5-24.9 | Normal weight | 25-35 lbs (11.5-16 kg) |
| 25.0-29.9 | Overweight | 15-25 lbs (7-11.5 kg) |
| 30.0+ | Obese | 11-20 lbs (5-9 kg) |
Weight Gain by Trimester
- First trimester (weeks 1-12): Minimal gain, typically 1-4 lbs total. Some women lose weight due to morning sickness.
- Second trimester (weeks 13-26): Steady gain of approximately 0.5-1 lb per week.
- Third trimester (weeks 27-40): Continued gain of approximately 0.5-1 lb per week, with some slowing near the due date.
Where Does the Weight Go?
At full term, the typical weight distribution is: baby (7-8 lbs), placenta (1-2 lbs), amniotic fluid (2 lbs), uterine growth (2 lbs), breast tissue (1-3 lbs), increased blood volume (3-4 lbs), increased fluid (2-3 lbs), and maternal fat stores (5-9 lbs). This adds up to 23-35 lbs for a normal-weight pregnancy.
Important: Follow Your OB's Guidance
These are general guidelines. Your obstetrician or midwife may recommend different targets based on your individual health profile, pregnancy complications, or multiple pregnancies. Always follow your healthcare provider's specific recommendations over general guidelines. Gaining too little weight is as problematic as gaining too much - both can affect fetal development and maternal health.
Track Your Weight Gain
Use our free Pregnancy Weight Gain Calculator to see where your weight gain falls relative to ACOG guidelines for your pre-pregnancy BMI and current trimester.
