"How much weight should I gain during pregnancy?" doesn't have a single universal answer — the recommended range depends on your BMI before pregnancy started.
Iom pregnancy weight guidelines, the four categories
The US Institute of Medicine's 2009 guidelines set four ranges: underweight (BMI under 18.5) at 12.5-18 kg, normal weight (18.5-24.9) at 11.5-16 kg, overweight (25-29.9) at 7-11.5 kg, and obese (30+) at 5-9 kg.
Pregnancy weight gain by bmi, a worked example
At 165 cm and a pre-pregnancy weight of 65 kg, BMI comes out to 23.9 — landing in the normal weight category, with a recommended total gain of 11.5 to 16 kg over the pregnancy.
Healthy weight gain during pregnancy, why the range varies
Someone starting underweight is recommended to gain more, since they typically have less reserve; someone starting in a higher BMI category is recommended to gain less. These are population-level guidelines — multiples, individual health conditions, and provider guidance can all shift the right number for a specific pregnancy.
