Extra Risks of Extra Pregnancy Pounds

Overweight and obese pregnant women at higher risk for pregnancy complications

/ Author:  / Reviewed by: Chris Galloway, M.D.

(RxWiki News) Gaining weight is a natural part of growing a baby in your womb. Being overweight or obese while you are pregnant, however, can carry additional risks for your pregnancy.

A recent study looked at what those risks are, based on a woman's weight. The researchers found increasing risks for different pregnancy complications as women were more overweight or obese.

Overweight and obese pregnant women were at a higher risk for gestational diabetes and high blood pressure. They also faced higher risks for needing birth interventions and bleeding during delivery than normal weight women.

"Attend all prenatal appointments."

The study, led by R. Scott Pillai, of the School of Nursing and Midwifery at Queen's University in Belfast, United Kingdom, looked for an association between a woman's weight while pregnant and whether she or her baby experienced any pregnancy complications.

The researchers investigated 30,298 pregnancies with single children (not twins, triplets, etc.) from 2004 to 2011. The researchers categorized the women according to their weight using their body mass index (BMI).

BMI is a ratio of a person's height to weight and is used to determine whether a person is a healthy weight or not.

Underweight was classified as having a BMI under 18.5. Normal weight was classified as a BMI between 18.5 and 24.9. An overweight woman would have a BMI of 25 to 29.9, and women with a BMI of 30 or higher were considered obese.

The researchers looked at women's risk of having high blood pressure, gestational diabetes, the need to have labor induced and a list of other pregnancy outcomes.

The results showed that women who were overweight or obese were at higher risk for developing several different complications of pregnancy.

Overweight and obese pregnant women were twice as likely to develop high blood pressure during pregnancy and 1.7 times more likely to develop gestational diabetes.

Overweight and obese women were at a slightly higher risk – 20 percent more likely (1.2 times) – to have labor induced, and they were 40 percent more likely to need a C-section.

Obese women were also 40 percent more likely to experience postpartum hemorrhage and 50 percent more likely to have a baby who was oversized for the week of pregnancy when the baby was born. A postpartum hemorrhage is excessive bleeding after the delivery.

As women increased in obesity with BMIs over 35 and 40, their risks for these outcomes continued to increase. Women in the highest obesity group, with BMIs at 40 and higher, were 60 percent more likely to deliver a baby early, before the 37th week of pregnancy, and to have a baby who needed additional care in the neonatal intensive care unit (NICU).

Women with the highest level of obesity were also at three times the risk for having a stillbirth compared to normal weight women, and they were twice as likely to stay in the hospital for more than five days after giving birth.

According to Dr. Yvonne Bohn, an OB/GYN at Good Samaritan Hospital in Los Angeles, the bottom line is that being overweight or obese during pregnancy can be particularly risky for a woman.

"The study shows that all of the major obstetrical complications — diabetes, hypertension, preterm birth and still birth — are increased for women that are overweight or obese," Dr. Bohn said.

She said rates of C section are higher for overweight women but almost a guarantee for obese women.

"The best thing a woman can do is to lose weight before conceiving," Dr. Bohn said. "A woman should know what her BMI is so she can have a realistic understanding of what her weight is."

If a woman is already overweight or obese while pregnant, however, there are still things she can do to minimize her risks.

"If a woman finds herself overweight or obese and is pregnant at least gaining the minimal amount of weight will help reduce some of her risks for the complications above," Dr. Bohn said.

She said the recommended weight gain for underweight women is 28-40 pounds. For normal weight  women, it's 25-35 pounds. For overweight women, it's 15-25 pounds, and for obese women, it's 11-20 pounds.

The study was published March 27 in BJOG: An International Journal of Obstetrics and Gynaecology. The research did not receive any external funding. The authors declared no conflicts of interest.

Reviewed by: 
Review Date: 
March 29, 2013
Last Updated:
July 23, 2013