Most women should gain between 25 and 35 pounds during pregnancy, though the right number depends on your weight before you became pregnant. The current guidelines, set by the Institute of Medicine and still used by the CDC and major obstetric organizations, base their recommendations on your pre-pregnancy BMI.
Recommended Gain by Starting Weight
Your pre-pregnancy BMI is the single biggest factor in determining how much weight you should gain. The ranges for a single baby are:
- Underweight (BMI below 18.5): 28 to 40 pounds
- Normal weight (BMI 18.5 to 24.9): 25 to 35 pounds
- Overweight (BMI 25.0 to 29.9): 15 to 25 pounds
- Obese (BMI 30.0 to 39.9): 11 to 20 pounds
The pattern is straightforward: the more you weigh going in, the less additional weight your body needs to put on for a healthy pregnancy. Women who start underweight need more gain to support both the baby and their own nutritional reserves.
Twin Pregnancy Targets
Carrying two babies increases the recommended range significantly. The guidelines for twins:
- Underweight: 50 to 62 pounds
- Normal weight: 37 to 54 pounds
- Overweight: 31 to 50 pounds
- Obese: 25 to 42 pounds
These wider ranges reflect the extra demands of growing two placentas, supporting a larger blood volume, and nourishing two babies simultaneously.
Where the Weight Actually Goes
Pregnancy weight gain isn’t just body fat. A full-term baby typically weighs 6 to 8 pounds, but the rest is distributed across structures your body builds to support the pregnancy. The placenta adds about 1.5 pounds. Amniotic fluid accounts for roughly 2 pounds. Your uterus grows from a few ounces to about 2 pounds. Breast tissue adds another pound or so. Your blood volume increases by about 3 to 4 pounds, and your body retains extra fluid adding several more pounds. Maternal fat stores, which your body lays down as energy reserves for breastfeeding, make up the remainder.
This breakdown explains why even women who gain within the guidelines don’t lose all the weight the moment the baby is born. Only about a third of it leaves with delivery itself.
How Gain Distributes Across Trimesters
Weight gain in the first trimester is minimal for most women, typically 1 to 4 pounds total. Some women actually lose weight early on due to nausea. The real accumulation happens in the second and third trimesters, when the baby is growing rapidly and your body is building up blood volume and fluid reserves. During these later months, gaining roughly a pound per week is typical for normal-weight women, slightly less for those who started at a higher weight.
Calorie needs follow a similar curve. You don’t need extra calories during the first trimester at all. In the second trimester, about 400 additional calories per day supports the increased demand, rising to roughly 600 extra calories per day in the third trimester. That’s less than most people assume. An extra 300 calories, the commonly cited average across the whole pregnancy, is roughly equivalent to a banana with peanut butter and a glass of milk.
Risks of Gaining Too Much
A large meta-analysis of data from 1.6 million women found that gaining above the recommended range carries measurable risks. Women who exceeded the guidelines had a 37% higher chance of needing a cesarean delivery and a 37% higher risk of developing high blood pressure disorders during pregnancy, including preeclampsia. Their babies were 77% more likely to be born large for gestational age and 78% more likely to meet the threshold for macrosomia (a birth weight over about 8 pounds 13 ounces), which increases the chance of birth injuries and complications during delivery. Babies born to mothers who gained excessively were also 26% more likely to need time in the NICU.
Excess weight gain also makes it harder to return to your pre-pregnancy weight afterward. Women who gain well above the guidelines retain more weight at the one-year mark, which can compound with subsequent pregnancies.
Risks of Gaining Too Little
Gaining below the recommended range comes with its own set of concerns, though they look different. The same large analysis found that inadequate gain was associated with a higher risk of preterm birth and a greater chance of the baby being born small for gestational age. Babies who are too small at birth face higher risks of breathing problems, difficulty regulating temperature, and feeding challenges in the first days of life.
For women who started pregnancy at a higher weight, the relationship between low gain and outcomes is more nuanced. Some research suggests that women with obesity who gain below the guidelines may not face the same degree of risk as underweight or normal-weight women who fall short. But for most women, consistently falling below the target range warrants a closer look at nutrition and overall health during pregnancy.
What to Expect After Delivery
Most women lose about half of their pregnancy weight by six weeks postpartum. That initial drop comes from the baby, placenta, amniotic fluid, and the rapid shedding of extra fluid your body retained. The remaining weight typically takes longer to come off, and the general expectation is a return to pre-pregnancy weight somewhere between 6 and 12 months after delivery.
Breastfeeding can accelerate this process because it burns several hundred extra calories a day, drawing on those fat stores your body built during pregnancy. But the timeline varies widely from person to person. Women who gained within the recommended range generally have an easier time returning to their starting weight than those who significantly overshot it.