And that number is on the increase.
Specifically, the study found that in 2015 only 45.1 percent of American women began pregnancy at a healthy weight, down from 47.3 percent in 2011. A healthy weight is defined as a body mass index (BMI) of 18.5 to 24.9.
It’s a disturbing trend. As background information in the report points out, pregnant women who are underweight (a BMI of less than 18.5), overweight (a BMI of 25.0 to 29.9) or obese (a BMI of 30 or higher) are at increased risk of pregnancy- and childbirth-related complications. Their babies are also at greater risk of being born with health problems. Being underweight before pregnancy increases the chances of having a smaller-than-average baby at birth, for example, while being overweight or obese increases the odds for a Caesarean-section delivery.
The increase in women entering pregnancy at an unhealthy weight threatens to intensify what is already a major health crisis in the United States: the unacceptably high number of women who die as a result of pregnancy- and childbirth-related complications.
As an investigative report published last year by ProPublica and National Public Radio (NPR) noted, 700 to 900 women in the U.S. die from such complications each year, and another 65,000 women almost die. Those numbers are, “by many measures, the worst in the developed world,” the two news organizations pointed out.
Health experts say that at least 60 percent of maternal deaths in the U.S. are preventable.
For the CDC report, researchers analyzed 2011-2015 birth data collected from the National Vital Statistics System for 48 states and two cities, New York City and Washington, D.C. That data included the mother’s prepregnancy BMI.
During those five years, the prevalence of women nationally who were at a healthy weight at the start of pregnancy dropped 5 percent, while it increased 8 percent for those who were obese and 2 percent for those who were overweight.
The only positive overall trend was the prevalence of women who were underweight when they became pregnant: that number fell by 8 percent.
A total of 38 jurisdictions (36 states and both cities) had a smaller proportion of pregnant women at a healthy weight in 2015 than in 2011.
Minnesota was, unfortunately, among those states. In 2015, 43.8 percent of Minnesota women who became pregnant were at a healthy weight, compared to 45.5 percent in 2012. (The state did not have available data for 2011.)
Minnesota did do better, however, than two of its nearest neighbors. In 2015, 41.7 percent of Wisconsin women and 40.2 percent of North Dakota women were at a healthy weight when they became pregnant.
But Minnesota did not do as well as its other two near-neighbors. In Iowa, 44.6 percent of women began pregnancy in 2015 at a healthy weight, while in South Dakota 46.5 percent did.
Nationally, the results for the jurisdictions ranged from 37.7 percent in Mississippi to 52.2 percent in Washington, D.C.
Interestingly, New York City had a relatively high prevalence of women who started pregnancy in 2015 at a healthy weight (52.1 percent), but it also had a high prevalence of women who began their pregnancies underweight (5.4 percent). (In Minnesota, 2.2 percent of women who became pregnant in 2015 were underweight.)
Three states — Arkansas, Kentucky and West Virginia — had the “double burden” of both a high prevalence of women who were overweight when they became pregnant and a high prevalence of women who were underweight.
The report recommends that all women of reproductive age undergo BMI screening during routine doctor visits and that doctors use those opportunities to talk to the women about the importance of being at a healthy weight before becoming pregnant.
FMI: The CDC report was published online in the Jan. 5 issue of Morbidity and Mortality Weekly Report (MMWR), where it can be read in full. I also recommend the investigative report by ProPublica and NPR on the U.S. pregnancy and childbirth health crisis, which can be found on ProPublica’s website.