What is the expected rate of weight gain during pregnancy?

Expected Rate of Weight Gain During Pregnancy

Weight gain during pregnancy is not linear and varies by trimester, with approximately 1.6-2.2 kg (3.5-4.8 lbs) gained in the first trimester, 0.5-0.6 kg (1.1-1.3 lbs) per week in the second trimester, and 0.5 kg (1.1 lbs) per week in the third trimester. 1

Weight Gain Recommendations Based on Pre-Pregnancy BMI

The recommended total weight gain during pregnancy varies according to pre-pregnancy BMI:

• Underweight women (BMI <18.5 kg/m²): 12.5-18 kg (28-40 lbs) 1, 2
• Normal weight women (BMI 18.5-24.9 kg/m²): 11.5-16 kg (25-35 lbs) 1, 2
• Overweight women (BMI 25.0-29.9 kg/m²): 7-11.5 kg (15-25 lbs) 1, 2
• Obese women (BMI ≥30.0 kg/m²): 5-9 kg (11-20 lbs) 1, 2

For women with normal weight, this typically translates to:

• First trimester: 1.4-2.3 kg total
• Second and third trimesters: 0.5-0.9 kg per week 3

For overweight women, the recommended rate is less than 50% of these rates 3.

Trimester-Specific Weight Gain Patterns

Weight gain during pregnancy follows a specific pattern:

1. First trimester: Minimal weight gain of 1.6-2.2 kg (3.5-4.8 lbs)
2. Second trimester: More rapid weight gain of 0.5-0.6 kg (1.1-1.3 lbs) per week
3. Third trimester: Continued steady weight gain of approximately 0.5 kg (1.1 lbs) per week 1

Clinical Implications of Weight Gain

Risks of Excessive Weight Gain

• Gestational hypertension and pre-eclampsia
• Gestational diabetes
• Higher risk for cesarean delivery
• Increased risk of macrosomia (birth weight ≥4000g)
• Long-term risk of maternal and childhood obesity 1, 2

Research shows that women with high weight gain are 54.5% more likely to give birth to infants ≥4000 grams compared to women with normal (31.7%) or low weight gain (13.8%) 2.

Risks of Inadequate Weight Gain

• Poor fetal growth
• Preterm birth
• Difficulty establishing breastfeeding 3

Special Considerations

• Multiple pregnancies: Women carrying twins or triplets require higher weight gain targets 1
• Adolescents: Younger women typically gain more weight during pregnancy 1
• Obesity class: Weight gain recommendations should be personalized considering different obesity classes (I, II, III) 4

Important Clinical Cautions

1. Weight reduction during pregnancy is not recommended, even for obese women, as it can lead to reduced neonatal weight and slower subsequent growth 1

2. Excessive weight gain is increasingly common, with approximately 40% of normal-weight and 60% of overweight women gaining excessive weight during pregnancy 5

3. Optimal fetal outcomes (in terms of Apgar scores and umbilical cord blood pH) are associated with adherence to recommended weight gain guidelines 2

4. Healthcare providers should proactively discuss appropriate weight gain targets with pregnant women early in pregnancy 1