Pregnancy gain should track a curve, not a guess. Institute of Medicine guidance sets weekly rates by pre pregnancy BMI, roughly half a kilogram weekly for underweight mothers in later trimesters down to a quarter for obese, after a small first trimester total. Enter your week and BMI class to see the expected gain to this point, then compare with your actual figure.
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Scientific references
Every antenatal visit weighs the mother because the curve tells a story. Too little gain links to small babies and preterm birth, too much to large babies, cesarean delivery and weight that lingers for years. The 2009 Institute of Medicine guidelines remain the global reference for what the curve should look like.
The Two Phase Pattern
The first trimester adds surprisingly little, a half to two kilograms total, because the baby itself still weighs grams. Weekly gain then begins, and its rate depends on starting BMI, about zero point five one kilograms weekly for underweight mothers, zero point four two for normal weight, zero point two eight for overweight and zero point two two for obese. Applied to a normal weight mother, week twenty eight should show roughly seven to eight kilograms gained.
Where the Weight Goes
A full term gain of eleven to sixteen kilograms for normal BMI mothers distributes far beyond the baby, placenta, amniotic fluid, uterus growth, blood volume, breast tissue and a deliberate fat reserve for breastfeeding each claim a share. Understanding that inventory defuses the common alarm at numbers that feel like pure body fat.
Tracking Against Your Own Curve
Single weigh ins matter less than trajectory. A week of stagnation means little, a month of it, or a sudden surge, deserves discussion. Surges late in pregnancy combined with headache or swelling can signal preeclampsia and warrant prompt review rather than diet changes.
These targets assume singleton pregnancies, twins carry their own higher schedules. And no guideline justifies restricting intake to hit a number, quality of food and steady gain together outrank any curve.