Pregnancy Weight Gain Calculator

Understanding Pregnancy Weight Gain

Healthy weight gain during pregnancy is essential for both maternal health and fetal development. The recommended weight gain varies based on your pre-pregnancy Body Mass Index (BMI) and whether you're carrying one baby or multiples.

IOM Weight Gain Guidelines

This calculator uses guidelines from the Institute of Medicine (IOM), now the National Academy of Medicine, which are widely adopted by healthcare providers:

Single Pregnancy Recommendations:

• Underweight (BMI < 18.5): 28-40 lbs (12.5-18 kg)
• Normal Weight (BMI 18.5-24.9): 25-35 lbs (11.5-16 kg)
• Overweight (BMI 25-29.9): 15-25 lbs (7-11.5 kg)
• Obese (BMI 30+): 11-20 lbs (5-9 kg)

Twin Pregnancy Recommendations:

• Normal Weight: 37-54 lbs (17-25 kg)
• Overweight: 31-50 lbs (14-23 kg)
• Obese: 25-42 lbs (11-19 kg)

Weight Gain by Trimester

First Trimester (Weeks 1-12)

Minimal weight gain is expected, typically 1-4.5 lbs total. Some women may even lose weight due to morning sickness.

Second Trimester (Weeks 13-26)

More consistent weight gain begins, approximately 1 lb per week for normal-weight women. This is when the baby grows rapidly.

Third Trimester (Weeks 27-40)

Weight gain continues at about 1 lb per week. Near the end, some women may notice a plateau or slight decrease as the due date approaches.

Where Does the Weight Go?

Understanding the distribution of pregnancy weight gain:

• Baby: 7-8 lbs
• Placenta: 1.5 lbs
• Amniotic fluid: 2 lbs
• Uterus growth: 2 lbs
• Breast tissue: 2 lbs
• Blood volume: 4 lbs
• Fat stores for delivery and breastfeeding: 5-9 lbs
• Increased fluid volume: 4 lbs

Tips for Healthy Weight Gain

• Eat nutrient-dense foods rather than "eating for two"
• Stay physically active with your doctor's approval
• Attend all prenatal appointments for monitoring
• Focus on quality of calories, not just quantity
• Stay hydrated with plenty of water