Health IOM 2009 Guidelines

Pregnancy Weight Gain Calculator

Find your recommended gestational weight gain range based on pre-pregnancy BMI. Week-by-week tracking and IOM 2009 guidelines for singleton and twin pregnancies.

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Pre-Pregnancy Weight

Current Week of Pregnancy

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Current Weight (optional)

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Pre-pregnancy height and weight plus current week to get your personalised weight gain target.

IOM 2009 Pregnancy Weight Gain Guidelines

Pre-Pregnancy BMI	Category	Total Gain	2nd–3rd Trim Rate
< 18.5	Underweight	12.5 – 18 kg	0.51 kg/wk
18.5 – 24.9	Normal weight	11.5 – 16 kg	0.42 kg/wk
25.0 – 29.9	Overweight	7 – 11.5 kg	0.28 kg/wk
≥ 30.0	Obese	5 – 9 kg	0.22 kg/wk
Twins: Normal 17–25 kg · Overweight 14–23 kg · Obese 11–19 kg

Source: Institute of Medicine (IOM) / National Academies. Weight Gain During Pregnancy: Reexamining the Guidelines. 2009.

Where Does the Weight Go?

Component	Weight Added
Baby	~3.2 – 3.6 kg
Placenta	~0.7 kg
Amniotic fluid	~0.8 kg
Uterus enlargement	~0.9 kg
Breast tissue	~0.9 kg
Blood volume increase	~1.5 kg
Body fluid increase	~1.5 kg
Maternal fat stores	~2.5 – 4 kg
Total (approx.)	11.5 – 16 kg