Being Big Less Risky After the First Baby

Obese pregnant women with low risk pregnancies have lower risks than first time moms

/ Author:  / Reviewed by: Robert Carlson, M.D Beth Bolt, RPh

(RxWiki News) Being overweight and pregnant has previously been shown to increase risks during delivery — but there may be more to the story than just a woman's weight that influences her risks.

A recent study found that a major part of the risk equation relates to whether a woman is pregnant for the first time or not.

For obese women delivering their first child, the risk of complications during delivery were higher than those of obese women delivering a child that wasn't their first.

Further, even women with a healthy weight and otherwise low-risk first-time pregnancy had higher risks for complications than low-risk, obese women having an additional child.

"Discuss your weight with your OB/GYN."

The study, led by Jennifer Hollowell, of the National Perinatal Epidemiology Unit at the University of Oxford in the United Kingdom, investigated how much a woman's weight affected her pregnancy outcomes if she was otherwise low risk.

The researchers tracked 17,230 women who had low-risk pregnancies; they did not have any medical or obstetric risk factors other than those who were obese.

Those who were obese were considered so if they had a body mass index (BMI) of 35 or greater. BMI is a ratio of a person's height to weight and is used to determine how healthy his or her weight is.

The researchers assessed women's pre-pregnancy weight and then looked at how common various pregnancy or delivery complications were among the women.

These compilations could include the following:

  • requiring labor augmentation (medical help continuing in labor)
  • requiring help from an instrument (such as a vacuum or forceps) for delivery
  • requiring a cesarean section
  • requiring general anesthesia (instead of an epidural or localized anesthesia)
  • requiring a blood transfusion
  • experiencing a 3rd-degree or 4th-degree perineal tear
  • having a baby who needed to be admitted to the neonatal intensive care unit (NICU)
  • having a baby who died

The researchers did find that obese (otherwise low-risk) women were more likely to need labor augmentation, a C-section or to experience another complication, but the risk overall was very small.

The increased risk was only 1.12 times greater than the risks for low-risk pregnant women who were not obese.

Further, the researchers found that low-risk obese women who were having an additional child (not their first) had lower risks of negative outcomes than low-risk women with a normal weight who were having their first child.

Approximately 53 percent of low-risk, healthy-weight women having their first child needed some kind of obstetric intervention, such as a delivery requiring instruments or a C-section.

By comparison, only 21 percent of low-risk, obese women having an additional child required an obstetric intervention.

This pattern was similar in looking at the risks for the newborns in admission to NICU or death.

"Otherwise healthy multiparous obese women may have lower intrapartum risks than previously appreciated," the researchers wrote. The researchers said it's important that doctors consider whether a woman is having her first child or is having an additional child in assessing her risks.

At the same time, however, in the overall sample of women, those who were overweight or obese were more likely to have additional risk factors than those who had a healthy weight.

Therefore, healthcare providers should consider all the possible risk factors for each individual woman during her pregnancy.

Risks for obese women having a first child continued to be higher than those of women at a healthy weight or those who were obese and having an additional child.

For example, 7.1 percent of low-risk, obese women having their first child had a newborn who required admission to the NICU or died.

Meanwhile, only 2.9 percent of low-risk, obese women having an additional child had a newborn who required NICU admission or who died.

The study was published September 11 in BJOG: An International Journal of Obstetrics & Gynaecology. The authors declared no conflicts of interest.

The research was funded by the Policy Research Program in the Department of Health in England. Data is also included that was funded by the National Institute for Health Research Service Delivery and Organization.

Review Date: 
September 18, 2013
Last Updated:
September 19, 2013