How much weight should I gain during pregnancy?

It depends on your pre-pregnancy BMI. The Institute of Medicine (IOM) guidelines recommend: underweight (BMI <18.5) gain 28-40 lb; normal weight (18.5-24.9) gain 25-35 lb; overweight (25-29.9) gain 15-25 lb; obese (≥30) gain 11-20 lb. These ranges are for singleton pregnancies — twins require more.

Where does pregnancy weight actually go?

For a typical 30 lb gain: baby 7-8 lb, placenta 1-2 lb, amniotic fluid 2 lb, uterus 2 lb, breast tissue 2 lb, blood volume 4 lb, and maternal fat/fluid stores 8-10 lb. The maternal stores support breastfeeding after delivery — your body is preparing to provide.

Is it safe to lose weight during pregnancy?

No — pregnancy is not the time for weight loss, even with a higher starting BMI. Restricting calories can harm fetal development. The goal for women with higher BMIs is slower weight gain, not loss. Focus on nutrient density rather than weight control.

What's the weekly gain rate in each trimester?

First trimester: 1-4 lb total (very little). Second and third trimesters: for normal BMI women, about 1 lb per week. Overweight women target about 0.6 lb/week, obese women about 0.5 lb/week. Gains much faster or slower than this warrant a conversation with your OB.

I'm having twins. How much more should I gain?

For twin pregnancies: normal BMI 37-54 lb, overweight 31-50 lb, obese 25-42 lb. (Underweight BMI has no twin guideline due to limited data.) Twin gains should be front-loaded — good progress by 24 weeks is predictive of healthy birthweights.

What if I gain too much or too little?

Excessive gain increases risk of gestational diabetes, preeclampsia, C-section, and higher childhood obesity in the baby. Insufficient gain increases risk of preterm birth and low birthweight. If you're tracking outside the range, talk to your provider — don't try to correct with crash dieting or overeating.

Pregnancy Weight Gain Calculator

Track healthy weight gain during pregnancy based on IOM guidelines.

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IOM Pregnancy Weight Gain Guidelines

The Institute of Medicine released updated pregnancy weight gain guidelines in 2009 after reviewing outcomes from thousands of pregnancies. They're based on pre-pregnancy BMI because women entering pregnancy at different sizes have different fat stores available to support fetal growth.

Singleton Pregnancy

Pre-pregnancy BMI	Total gain (lb)	Weekly (2nd/3rd tri)
Underweight (< 18.5)	28 – 40	1.0 – 1.3 lb
Normal (18.5 – 24.9)	25 – 35	0.8 – 1.0 lb
Overweight (25 – 29.9)	15 – 25	0.5 – 0.7 lb
Obese (≥ 30)	11 – 20	0.4 – 0.6 lb

First Trimester Is Flat

Most women gain very little in the first 13 weeks — 1 to 4 pounds is typical, and some lose a little due to nausea. Gain accelerates in the second trimester and stays steady through the third. Rapid early gain isn't dangerous, but it's worth discussing with your OB.

Quality Over Quantity

Weight gain is a rough proxy for nutrition. A woman hitting her numbers on ultra-processed foods is not in the same nutritional position as one eating whole foods. Prenatal vitamins, adequate protein (about 1.1 g/kg), iron, folate, choline, and omega-3s matter more than the scale.

Guidance, Not Medical Advice

Every pregnancy is different. Work with your obstetrician or midwife for personalized recommendations, especially if you have gestational diabetes, hypertension, a history of pregnancy complications, or are carrying multiples.

Pregnancy Weight Gain Calculator

IOM Pregnancy Weight Gain Guidelines

Singleton Pregnancy

First Trimester Is Flat

Quality Over Quantity

Guidance, Not Medical Advice

Frequently Asked Questions

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