What Your Pre-Baby Weight Means for Your Pregnancy

Reviewed by Hansa D. Bhargava, MD on March 06, 2021

Women who’ve never paid attention to the scale need to be more numbers conscious during pregnancy. Doctors have long recommended checks on weight gain during pregnancy. Yet according to research, the weight you carry into your pregnancy matters even more than how much you put on during it. Going into your pregnancy overweight or obese increases your odds of complications even more than gaining too much weight during those 9 months, according to a recent study in JAMA.

Miscarriage, high blood pressure (preeclampsia), gestational diabetes, preterm birth, and C-section delivery are all concerns for moms with obesity. They may also have a longer labor and slower healing afterward, says Michelle Kominiarek, MD, associate professor in the department of Obstetrics and Gynecology, Northwestern University Division of Maternal-Fetal Medicine. “The higher the weight or the greater the BMI, the higher the risk for complications,” she adds.

As soon as you start thinking about parenthood, consider whether you’re at an optimal weight. How much you need to lose before conceiving depends on whom you ask. “Some societies recommend achieving a normal BMI before pregnancy, but for some women that may be a difficult demand,” Kominiarek says. Losing 5% to 7% of your weight -- about 10 to 20 pounds -- is a more realistic goal. That minimal amount of weight loss could also improve your odds of conceiving.

Women with a BMI of 40, or a 35 BMI plus conditions like diabetes or high blood pressure, may be good candidates for bariatric surgery. Plan to wait for a year or two after the procedure to get down to your goal weight and give your body time to adjust before you get pregnant. Once you do conceive, you’ll be at lower risk for complications like high blood pressure or diabetes after the surgery.

Entering your pregnancy heavier than you’d like can still lead to a healthy outcome. Work with your doctor to control weight gain, and get regular monitoring for possible complications. “We typically screen for diabetes during pregnancy at around 24 to 28 weeks, but sometimes in women with particular risk factors, including a higher BMI, we screen earlier,” Kominiarek says.

Women with a BMI higher than 40 should also have nonstress tests weekly starting at around week 36 until they deliver. This test places a belt around your belly to monitor your baby’s heartbeat and activity level. Or, you might get a biophysical profile, which evaluates the baby’s heart rate, breathing, movement, and amniotic fluid level. A low score could indicate the need for an early delivery.

If you haven’t reached your goal weight by the time you conceive, pregnancy isn’t the time to diet. “I never recommend that anyone lose weight during pregnancy,” Kominiarek says. If you eat too little, your body will mobilize your own nutrient stores to support your growing baby. Save the dieting for after you deliver, and add in some gentle exercise once you’re ready to help you shed that pre- and post-baby weight.

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Show Sources


JAMA: “Association of gestational weight gain with adverse maternal and infant outcomes,” “Prepregnancy Body Mass Index, Weight Gain During Pregnancy, and Health Outcomes.”

Michelle Kominiarek, MD, associate professor in the department of Obstetrics and Gynecology, Northwestern University, Evanston, IL.

Human Reproduction: “Obesity and Time to Pregnancy.”

ACOG: “Obesity and Pregnancy,”  “AGOC Guidelines on Pregnancy After Bariatric Surgery,” “Weight Gain During Pregnancy.”

Mayo Clinic: “Biophysical profile.”

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