Most women gain between 25 and 35 pounds during pregnancy, but the right amount for you depends on your pre-pregnancy BMI. The guidelines set by the Institute of Medicine and endorsed by the CDC break recommendations into four categories based on starting weight, and the range spans from as little as 11 pounds to as much as 40.
Recommended Weight Gain by BMI
Your pre-pregnancy body mass index is the single biggest factor in how much weight you’re expected to gain. The CDC lists these targets for a single baby:
- Underweight (BMI under 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
These ranges exist because women who start pregnancy at a lower weight need more stored energy to support fetal growth, while women at higher weights already carry those reserves. The numbers are wide on purpose. A normal-weight woman who gains 26 pounds and one who gains 34 pounds are both within the healthy range.
Where the Weight Actually Goes
It can feel strange watching the scale climb, but most of the weight you gain isn’t body fat. A full-term baby accounts for roughly 7 to 8 pounds. The placenta adds another 1.5 pounds, and amniotic fluid contributes about 2 pounds. Your uterus grows from the size of a pear to the size of a watermelon, gaining around 2 pounds of muscle tissue in the process.
Beyond the baby and its support system, your body makes significant changes to keep everything running. Blood volume increases by nearly 50%, adding about 4 pounds. Breast tissue grows in preparation for milk production, contributing another 1 to 2 pounds. Fluid retention accounts for a few more pounds, and the remainder is maternal fat stores, which your body uses as an energy reserve for labor, recovery, and breastfeeding. Altogether, the non-fat components alone account for roughly 17 to 20 pounds.
When the Weight Comes On
Weight gain during pregnancy isn’t evenly distributed across all 40 weeks. The first trimester is relatively quiet. Many women gain only 1 to 4 pounds in those first 13 weeks, and some actually lose weight due to nausea. That’s completely normal. The real growth phase begins in the second trimester.
From about week 14 onward, steady gain matters most. Women at a healthy starting weight typically gain around 1 pound per week through the second and third trimesters. If you started pregnancy overweight or obese, the target is closer to half a pound per week during that same stretch. Studies show the average rate of gain is roughly 1 pound per week during the second trimester, tapering slightly to about 0.9 pounds per week in the third trimester, though individual variation is wide.
Don’t worry too much about week-to-week fluctuations. Water retention, meal timing, and even the time of day you step on the scale can shift things by a pound or two. The overall trend across weeks matters more than any single weigh-in.
Weight Gain for Twin Pregnancies
Carrying twins changes the targets substantially. The American College of Obstetricians and Gynecologists recommends:
- Normal weight: 37 to 54 pounds
- Overweight: 31 to 50 pounds
- Obese: 25 to 42 pounds
The higher recommendations reflect the demands of growing two babies, two placentas, and a significantly larger blood volume. Women carrying twins also tend to deliver earlier, so gaining at a steady pace from early in the second trimester is especially important.
Risks of Gaining Too Much
Exceeding the recommended range raises the likelihood of several complications. For the baby, excessive maternal weight gain increases the chance of macrosomia, meaning the baby is significantly larger than average at birth. Larger babies are more likely to require a cesarean delivery and face a higher risk of shoulder injuries during vaginal birth.
For you, gaining well above the guidelines increases the risk of gestational diabetes, preeclampsia (dangerously high blood pressure), and a harder postpartum recovery. Excess weight gained during pregnancy is also more difficult to lose afterward, and research consistently links it to long-term weight retention years after delivery.
Risks of Gaining Too Little
Gaining less than the recommended amount carries its own set of concerns, particularly preterm birth and low birth weight. A large meta-analysis found that women with low total weight gain were 64% more likely to deliver before 37 weeks and 85% more likely to have a baby weighing under 5.5 pounds. The risks increased as weight gain dropped further: women with very low gain were nearly four times more likely to deliver at or before 32 weeks compared to women who gained within the normal range.
Low birth weight and prematurity are associated with breathing difficulties, feeding problems, and longer hospital stays for newborns. If morning sickness, food aversions, or other factors are making it hard to gain weight, that’s worth flagging to your provider early rather than waiting for a later appointment.
What Happens After Delivery
You won’t walk out of the hospital at your pre-pregnancy weight, but a significant chunk comes off quickly. Most women lose roughly 11 to 13 pounds immediately after birth, which accounts for the baby, placenta, amniotic fluid, and some blood and fluid loss. Another 4 to 5 pounds typically come off over the following few weeks as your body sheds retained fluid and your uterus shrinks back toward its original size.
That means within the first month postpartum, roughly 15 to 18 pounds are gone without any deliberate effort. The remaining weight, mostly maternal fat stores, comes off more gradually. For women who gained within the recommended range, returning to pre-pregnancy weight typically takes 6 to 12 months, though breastfeeding, sleep patterns, and activity level all influence the timeline.