How your weight can affect your pregnancy

Approximately 35 percent of adult Americans, or 1 in 3 people, are now obese. Obesity is defined as having a body mass index (BMI) of 30 or above. While we know many complications associated with obesity, being pregnant and obese has its own special issues.

Obesity increases the risks of many maternal complications. For example, rates of gestational diabetes in obese women are about double of those in normal weight women, with 12 percent of obese women ruling in for this diagnosis. The risk of developing high blood pressure during pregnancy, as well as preeclampsia, is also twice as high for obese pregnant women. Preterm birth is also more common in this group, though this might be partially because of the need to deliver early because of certain complications. Interestingly, postterm pregnancy is also more common in obese women.

When it comes to problems during delivery, these too are more common if you are obese. Induced labor is more frequent, again partially because of the need to be delivered before labor has spontaneously occurred if a medical complication is present. Labor is more likely to take longer (even in labors that are not induced), but doctors aren’t quite sure why this is.

Rates of C-section are higher in obese women, with approximately 33 percent of obese first-time moms delivering this way (and that number jumps to 43 percent if a woman’s BMI is above 35). This is worrisome as obese women are more likely to have surgical complications, such as heavy bleeding, blood clots, and wound infections or separations.

The developing babies of obese women also suffer more complications. These babies are more likely to be abnormally large themselves, and they are more likely to eventually become obese as they get older. Rates of neural tube defects and other congenital abnormalities are higher in this group. Stillbirth is also more common. Ultrasounds are more likely to be incomplete or be unable to detect abnormalities as the mother’s weight makes it difficult to visualize the baby as easily, making monitoring somewhat difficult.

If a woman is obese and planning to become pregnant, the best thing she can do is make a preconception visit to her obstetric provider. A plan can be made to optimize her health before she becomes pregnant. This may include making a healthy weight loss plan, screening for diabetes or high blood pressure, and ensuring that she has appropriate weight gain during her pregnancy.

Reviewed by Dr. Jen Lincoln, April 2020