Pregnancy Weight Gain Calculator
Calculate recommended total weight gain for pregnancy based on pre-pregnancy BMI. Includes trimester-by-trimester targets and what the weight represents.
Pregnancy Weight Gain Guide
Recommended Weight Gain by BMI
The Institute of Medicine (IOM) and NHS use pre-pregnancy BMI to guide recommended total weight gain. Underweight (BMI < 18.5): 12.5–18 kg total. Normal weight (BMI 18.5–24.9): 11.5–16 kg total. Overweight (BMI 25–29.9): 7–11.5 kg total. Obese (BMI ≥ 30): 5–9 kg total. Twins: add approximately 5-7 kg to the singleton recommendation. First trimester: approximately 0.5-2 kg total is typical. Second and third trimesters: approximately 0.3-0.5 kg per week (normal weight women). These are guidelines
Where Pregnancy Weight Goes
The 11-16 kg weight gain for a normal-weight singleton pregnancy is distributed approximately as: baby: 3.2-4.0 kg. Placenta: 0.6-0.7 kg. Amniotic fluid: 0.8-1.0 kg. Uterus growth: 0.9 kg. Breast tissue increase: 0.4-1.4 kg. Blood volume increase (approximately 50%): 1.4-1.8 kg. Fluid retention: 1.0-2.0 kg. Maternal fat stores: 2.7-3.6 kg. Understanding this breakdown helps contextualise why a normal-weight pregnancy recommends 11-16 kg of gain — it is not all 'fat gain' but rather essential phy
Concerns with Insufficient Gain
Insufficient weight gain during pregnancy is associated with: intrauterine growth restriction (baby too small for gestational age), preterm birth, low birth weight, and in severe cases, perinatal mortality. Women who gained less than recommended are more likely to have low-birth-weight babies who face developmental challenges. Very restricted eating during pregnancy can deprive the developing baby of critical nutrients. If nausea, hyperemesis gravidarum, or other conditions prevent adequate gain
Concerns with Excessive Gain
Excessive weight gain is associated with: gestational diabetes, pre-eclampsia, larger babies (increasing difficulty of delivery and caesarean risk), postpartum weight retention, and longer-term obesity risk. For overweight and obese women, the recommended weight gain is intentionally lower — this reflects evidence that excessive gain in these groups carries higher risks. However, weight loss during pregnancy is not recommended for obese women — even at high BMI, some gain is expected. Physical a
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