Pregnancy topic

Pregnancy Weight Gain

Recommended range by BMI, weekly targets, gaining too much or too little

Healthy pregnancy weight gain supports fetal development and maternal health. The Institute of Medicine (IOM/NAM) issues ranges by pre-pregnancy BMI. Too little raises the risk of low birth weight and preterm birth; too much raises the risk of gestational diabetes, hypertension, and difficult delivery.

Total recommended gain (singleton)

Based on your pre-pregnancy BMI (kg/m²):

Underweight (BMI < 18.5): 12.5 – 18 kg
Normal (BMI 18.5 – 24.9): 11.5 – 16 kg
Overweight (BMI 25 – 29.9): 7 – 11.5 kg
Obese (BMI ≥ 30): 5 – 9 kg

Pace by trimester

First (0–13 wk): 0.5 – 2 kg total. Loss from nausea is also normal.
Second (14–27 wk): ~0.4 – 0.5 kg per week (normal BMI).
Third (28–40 wk): ~0.4 – 0.5 kg per week. The last few weeks may slow.

Twin pregnancies

Normal BMI: 16.8 – 24.5 kg
Overweight: 14.1 – 22.7 kg
Obese: 11.3 – 19.1 kg

Where the weight goes

An average gain of about 12.5 kg breaks down roughly as:

Baby: 3.4 kg
Amniotic fluid: 0.9 kg
Placenta: 0.7 kg
Uterus: 0.9 kg
Breast tissue: 0.9 kg
Blood volume: 1.6 kg
Stores and fluid: 4.1 kg

Gaining too fast

Cut added sugars, juices, and refined carbs.
Add fiber, protein, and vegetables.
30 minutes of walking or swimming most days.
Sudden 1 kg/week gain with swelling or headaches — call your provider (preeclampsia possible).

Gaining too slowly

Severe nausea may be treatable — ask about medication.
Add nutrient-dense foods (nuts, avocado, cheese, nut butters).
Underweight pre-pregnancy BMI requires more proactive nutrition.