Institute of Medicine (IOM) pregnancy weight guidelines
Maternal weight gain supports fetal growth, amniotic fluid volume, expanded maternal blood volume, and placental tissue. The National Academies / Institute of Medicine (IOM) established international benchmarks based on pre-pregnancy BMI.
Women with normal pre-pregnancy BMI (18.5–24.9) should gain 25 to 35 lbs (11.5 to 16.0 kg) total, with 1 to 4.5 lbs gained during the first trimester, followed by approximately 1 lb (0.4 kg) per week in the second and third trimesters.
Underweight women require higher gain (28–40 lbs / 12.5–18.0 kg), while overweight (15–25 lbs / 7.0–11.5 kg) and obese (11–20 lbs / 5.0–9.0 kg) categories require moderated gain to minimize gestational diabetes and preeclampsia risks.
Worked example: Week 24 singleton progress
A woman with normal pre-pregnancy BMI (60 kg, 165 cm, BMI 22.0) is at 24 weeks gestation.
Expected weight gain at 24 weeks is 5.5 to 8.0 kg (12 to 17.5 lbs).
Current weight of 66 kg represents an on-track gain of 6.0 kg.
Weight gain inputs
Pre-pregnancy Weight & Height
Used to establish pre-pregnancy BMI category.
Gestational Weeks
Current completed pregnancy weeks.
CALCULATOR QUESTIONS
Healthy pregnancy weight gain & BMI calculator questions
Is it safe to lose weight while pregnant?
No. Active weight loss or calorie-restricted dieting is not recommended during pregnancy, even for women with obesity, as it can deprive the developing fetus of essential macronutrients and ketones.
Where does pregnancy weight gain actually go?
On average: Baby (7.5 lbs), Placenta (1.5 lbs), Amniotic fluid (2 lbs), Uterine growth (2 lbs), Breast tissue (2 lbs), Blood volume (4 lbs), Maternal fluid (4 lbs), and Maternal fat/nutrient stores (7 lbs).