Pregnancy BMI Calculator

Professional pregnancy weight-management tool: supports pre-pregnancy BMI assessment, IOM standard weight-gain ranges, gestational-diabetes risk prediction, personalized nutrition advice, real-time weight alerts, and helps moms control weight scientifically to lower pregnancy-complication risks.

Calculate Now Features

Maternal BMI Smart Assessment System

Weight management based on IOM guidelines, supporting singleton / twins / multiples, with personalized nutrition advice

Your actual weight before pregnancy
Weight measured today
Barefoot height
Used for risk assessment
Affects weight-gain standards
weeks
Counted from LMP
Affects risk evaluation
Important risk factor

Pregnancy BMI Knowledge

What is pregnancy BMI and why does it matter?

BMI (Body Mass Index) is a key indicator of healthy weight, calculated as BMI = weight(kg) ÷ height²(m²).

For pregnant women BMI affects not only conception chance but also maternal & infant health throughout pregnancy:

  • Pre-pregnancy BMI too low (<18.5): may increase risk of preterm birth & low-birth-weight babies
  • Normal pre-pregnancy BMI (18.5-24.9): optimal range for pregnancy
  • Pre-pregnancy BMI overweight (25-29.9): higher risk of gestational diabetes, hypertension
  • Pre-pregnancy BMI obese (≥30): significantly higher risks of miscarriage, macrosomia, dystocia
IOM Pregnancy Weight-gain Guidelines
Pre-pregnancy BMI Category BMI Range Suggested Gain (Singleton) Suggested Gain (Twins) Average Weekly Gain*
Underweight <18.5 12.5-18 kg No data 0.44-0.58 kg
Normal 18.5-24.9 11.5-16 kg 17-25 kg 0.35-0.50 kg
Overweight 25.0-29.9 7-11.5 kg 14-23 kg 0.23-0.33 kg
Obese ≥30.0 5-9 kg 11-19 kg 0.17-0.27 kg
*Average weekly gain in 2nd & 3rd trimester; 1st-trimester gain is small (0.5-2 kg)
Importance of Pregnancy Weight Management
Risks of Excessive Gain
  • 2-3× higher risk of gestational diabetes
  • Gestational hypertension, preeclampsia
  • Macrosomia (≥4 kg), difficult labor
  • Higher chance of cesarean section
  • Post-partum weight retention & obesity
  • Child's future obesity & metabolic risks
Risks of Insufficient Gain
  • Fetal growth restriction
  • Higher risk of preterm birth
  • Low-birth-weight infant (<2.5 kg)
  • Child's future health risks
  • Maternal malnutrition
  • Difficult post-partum recovery
Weight-management Tips

  • Same time daily (morning,空腹)
  • Use the same scale
  • Wear similar light clothes
  • After emptying bladder
  • Record date & time

  • Small frequent meals, 5-6 daily
  • Choose nutrient-dense foods
  • Increase high-quality protein
  • More fresh vegetables & fruit
  • Limit refined sugar & processed food
  • Stay well hydrated

  • Walking: 30 min daily
  • Prenatal yoga: 2-3×/week
  • Swimming: best full-body workout
  • Prenatal Pilates: core strength
  • Avoid vigorous & contact sports
  • Consult doctor before starting
Quick FAQ
Q: Severe nausea & weight loss?
A: Losing 1-2 kg in 1st trimester is normal; gain resumes in 2nd trimester
Q: Why is my gain slower than others?
A: Everyone is different; stay within recommended range
Q: Can I diet during pregnancy?
A: Deliberate weight-loss is not advised; control rate instead
Q: Does high BMI affect baby?
A: May increase risks of macrosomia, preterm birth, etc.

Why Choose PreMami Pregnancy BMI Calculator?

IOM Standard Authority

Based on the latest U.S. Institute of Medicine (IOM) guidelines, providing authoritative pregnancy weight-gain standards

Multiples Support

Separate weight-gain standards for singleton, twins, triplets+ pregnancies

Smart Curve Tracking

Real-time weight-gain curves with intelligent abnormal-gain alerts

Intelligent Risk Assessment

Evaluates risks of gestational diabetes, hypertension, etc., with prevention tips

Pregnancy BMI Calculator FAQ

Normal BMI only judges whether weight is healthy, whereas pregnancy BMI must combine pre-pregnancy BMI, gestational week, pregnancy type (singleton/twins), etc., using IOM standards made for pregnant women and accounting for unique physiological changes.

Pre-pregnancy BMI determines the whole-pregnancy weight-gain target, while current BMI reflects actual progress. Comparing the two can tell whether gain is reasonable and detect too-fast or too-slow problems early.

Twins need to support growth of two babies, more placenta & amniotic fluid, etc., so greater weight gain is required. IOM provides separate standards for twins, about 40-50 % higher than singleton.

First adjust diet: reduce refined sugar & processed food, increase vegetables & lean protein; then add moderate exercise such as prenatal yoga or walking; finally rule out pathological causes like gestational diabetes, and consult a dietitian if necessary.

Insufficient gain may lead to fetal-growth restriction, preterm birth, low-birth-weight infant, etc. Recommend increasing nutrient-dense foods, eating small frequent meals, and using prenatal supplements under doctor guidance when necessary.

Our risk assessment is based on large-scale clinical research data, integrating multiple risk factors such as age, BMI, family history, previous history, etc., and has high accuracy. However, final diagnosis still depends on medical tests like the glucose-tolerance test.