Life & Career · 孕期体重增长（Pregnancy Weight Gain） · Updated 2026-10-25
What Is Pregnancy Weight Gain?
Definition
Chinese pregnancy guidelines tier gain by pre-pregnancy BMI: underweight (<18.5) 12.5-18 kg; normal (18.5-24) 11.5-16 kg; overweight (24-28) 7.5-11.5 kg; obese (≥28) 5-9 kg. First trimester adds 0.5-2 kg total; weekly gains in later trimesters: 0.42 kg for under/normal, 0.28 kg overweight, 0.22 kg obese. Composition: fetus ~3.4 kg, placenta+fluid 1.5 kg, uterus+breasts 1.3 kg, blood volume 1.2 kg, fat stores 2-4 kg.
Formula
Normal BMI: 11.5-16 kg total; ~0.42 kg/week in 2nd-3rd trimesters
Worked Example
Pre-pregnancy 55 kg at 1.62 m (BMI 21); at week 28 weighing 62 kg — +7 kg, on track for a 66.5-71 kg endpoint. Gaining 9 kg by week 20 warrants diet and activity intervention.
Common Misconception
"Eating for two" — the second trimester needs only ~300 extra kcal/day (a glass of milk and an egg); excess gain sharply raises gestational diabetes and macrosomia risk. And "it comes off naturally" — fat stores linger 6-12 months without breastfeeding; retention above 5 kg predicts long-term obesity.
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