How much weight should I gain during pregnancy?

The Institute of Medicine (IOM) recommends different total weight gain ranges based on pre-pregnancy BMI: Underweight (BMI under 18.5): 28–40 lbs (12.7–18.1 kg). Normal weight (BMI 18.5–24.9): 25–35 lbs (11.3–15.9 kg). Overweight (BMI 25–29.9): 15–25 lbs (6.8–11.3 kg). Obese (BMI 30+): 11–20 lbs (5–9.1 kg). For twin pregnancies, the ranges are higher. Always discuss your personal target with your healthcare provider.

What is healthy pregnancy weight gain per week?

In the second and third trimesters (weeks 13–40), normal-weight women should gain approximately 1 pound (0.45 kg) per week. Underweight women may aim for slightly more (1–1.3 lbs/week); overweight women slightly less (0.6 lb/week); and obese women around 0.5 lb/week. In the first trimester, total gain is typically only 1–4.5 lbs (0.5–2 kg).

How much weight gain is normal in the first trimester?

Most women gain only 1–4.5 lbs (0.5–2 kg) in the first trimester (weeks 1–12). Some women with severe morning sickness may actually lose weight in the first trimester — this is usually not harmful if weight gain catches up later. The majority of pregnancy weight gain occurs in the second and third trimesters.

Pregnancy Weight Gain Guide: IOM Guidelines in lbs & kg by Trimester

IOM Recommended Weight Gain by Pre-Pregnancy BMI

The Institute of Medicine (IOM) — now the National Academy of Medicine — published updated pregnancy weight gain guidelines in 2009. These remain the standard reference used by OB-GYNs and midwives in the United States. Recommendations are based on pre-pregnancy BMI because a woman's starting body composition affects how much additional weight supports a healthy pregnancy.

Note: These are population-level guidelines. Your healthcare provider may recommend a different target based on your individual health history.

Pre-Pregnancy BMI	BMI Category	Total Gain (lbs)	Total Gain (kg)	2nd & 3rd Trimester Rate
Under 18.5	Underweight	28–40 lbs	12.7–18.1 kg	1–1.3 lbs/week
18.5–24.9	Normal weight	25–35 lbs	11.3–15.9 kg	~1 lb/week
25.0–29.9	Overweight	15–25 lbs	6.8–11.3 kg	0.5–0.7 lbs/week
30.0 and above	Obese	11–20 lbs	5.0–9.1 kg	0.4–0.6 lbs/week

Weight Gain by Trimester

Pregnancy is divided into three trimesters of roughly 13 weeks each. The distribution of weight gain is not uniform — most gain happens in the second and third trimesters as the baby grows rapidly.

Trimester	Weeks	Typical Gain (lbs)	Typical Gain (kg)	Notes
First trimester	1–12	1–4.5 lbs	0.5–2 kg	Nausea may limit gain; some lose weight
Second trimester	13–26	~12–14 lbs	~5.4–6.4 kg	~1 lb per week for normal-weight women
Third trimester	27–40	~8–11 lbs	~3.6–5 kg	Growth slows slightly in final weeks

Where the Weight Goes

For a woman of normal BMI gaining 30 lbs (13.6 kg) during a singleton pregnancy, the weight is approximately distributed as follows:

Baby: 7–8 lbs (3.2–3.6 kg)
Placenta: 1.5 lbs (0.7 kg)
Amniotic fluid: 2 lbs (0.9 kg)
Uterus growth: 2 lbs (0.9 kg)
Breast tissue: 2 lbs (0.9 kg)
Blood volume increase: 4 lbs (1.8 kg)
Body fluid (edema): 4 lbs (1.8 kg)
Maternal fat stores: 7 lbs (3.2 kg)

Twin and Multiple Pregnancies

IOM guidelines for twin pregnancies are higher. Normal-weight women carrying twins should gain 37–54 lbs (16.8–24.5 kg). Overweight women with twins: 31–50 lbs (14.1–22.7 kg). Obese women with twins: 25–42 lbs (11.3–19.1 kg). Triplet and higher-order pregnancy guidelines are set individually with the care team.

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