Losing some weight during pregnancy is common, especially in the first trimester. Most women who experience early weight loss go on to gain appropriately as the pregnancy progresses, and the temporary dip rarely affects the baby. That said, the amount of weight lost, the timing, and your starting weight all matter in determining whether it’s something to monitor more closely.
Why First Trimester Weight Loss Happens
Nausea and vomiting affect up to 80% of pregnant women in the first trimester, and when you’re struggling to keep food down, weight loss follows naturally. Women with significant morning sickness often lose weight early in pregnancy. For most, this resolves by weeks 14 to 16, and weight gain picks up from there.
Even without nausea, some women notice they lose a few pounds in the first trimester simply because their appetite changes, certain foods become unappealing, or they shift to lighter meals. The caloric demands of pregnancy don’t increase much in the first 12 weeks. Your body doesn’t need extra calories at that stage, so a small dip on the scale isn’t cause for alarm.
When Weight Loss Becomes a Concern
A small subset of women develop a severe form of nausea and vomiting called hyperemesis gravidarum. There’s no single accepted definition, but losing at least 5% of your pre-pregnancy body weight is a common marker. For someone who weighed 150 pounds before pregnancy, that’s roughly 7.5 pounds or more. Women with this condition often become dehydrated and may need medical support to stay nourished.
The CDC flags severe nausea as an urgent maternal warning sign when you’re unable to drink for more than 8 hours or eat for more than 24 hours, or when you can’t keep water or other fluids down at all. That level of vomiting goes beyond typical morning sickness and needs prompt attention.
Weight loss in the second or third trimester is less common and deserves closer monitoring. By the second trimester, your body needs about 2,200 calories a day (roughly 300 more than before pregnancy), rising to about 2,400 in the third trimester. If the scale is dropping during those months, something may be interfering with nutrition or fluid balance.
How Starting Weight Shapes Expectations
How much weight you’re expected to gain depends on your pre-pregnancy BMI, and the ranges vary quite a bit. For a singleton pregnancy, the general recommendations break down like this:
- Underweight (BMI under 18.5): 28 to 40 pounds total
- Normal weight (BMI 18.5 to 24.9): 25 to 35 pounds
- Overweight (BMI 25 to 29.9): 15 to 25 pounds
- Obese (BMI 30 or above): 11 to 20 pounds
For twin pregnancies, the targets are higher: 37 to 54 pounds for normal-weight women, 31 to 50 for overweight women, and 25 to 42 for obese women.
These numbers are total gain across the entire pregnancy. A slow start or a brief period of weight loss in the first trimester doesn’t mean you’ve fallen behind permanently. Most of the weight gain happens in the second and third trimesters as the baby, placenta, amniotic fluid, and your own blood volume all increase.
Weight Loss in Higher-BMI Pregnancies
If you started pregnancy at a higher weight, you may be wondering whether gaining less, or even losing weight, is safe. A large population-based study published in The Lancet in 2024 looked at exactly this question. For women with class 1 or class 2 obesity (BMI of 30 to 39.9), gaining below the recommended range or even gaining zero net weight by 40 weeks did not increase the risk of adverse outcomes for either mother or baby.
For women with class 3 obesity (BMI of 40 or higher), gaining below the guidelines or losing weight was actually associated with a reduced risk of complications. The researchers concluded that the current lower limits on recommended weight gain may be too high for women with obesity, and that separate, lower targets for class 3 obesity may be warranted.
This doesn’t mean intentional dieting during pregnancy is advisable. But it does mean that if you’re starting at a higher BMI and your weight stays flat or dips slightly, that pattern alone isn’t a red flag. Your provider can help you figure out a calorie range that supports fetal growth without pushing unnecessary weight gain.
Weight Loss Right Before Labor
In the final days before labor begins, some women notice the scale drops by 1 to 3 pounds. This is a normal physiological shift caused by changes in fluid retention as your body prepares for delivery. Hormone fluctuations in late pregnancy can trigger the release of extra water weight. If you’re full-term and notice a slight dip, it may simply be one of several signs that labor is approaching.
What to Pay Attention To
A few pounds lost in the first trimester, especially alongside nausea, is one of the most common experiences in pregnancy. It typically corrects itself as appetite returns. What matters more than any single weigh-in is the overall trend across your pregnancy. Steady, gradual gain through the second and third trimesters is the pattern providers look for.
Keep track of whether you’re able to stay hydrated and eat at least some food most days. If you’re losing weight persistently after the first trimester, losing more than 5% of your pre-pregnancy weight at any point, or unable to keep fluids down for extended stretches, those are signals worth raising with your provider sooner rather than later.