A growing number of women in the United States start their pregnancies with unhealthy weight. In 2014, more than half of women were either overweight or obese prior to becoming pregnant.

In a new report published in the National Vital Statistics Reports on Aug. 5, statistician Amy Branum, from the National Center for Health Statistics of the U.S. Centers for Disease Control and Prevention (CDC), and colleagues reported that among American women who gave birth in 2014, more than half are heavier than normal prior to pregnancy.

Only 45.9 percent of the women were of normal weight, and 3.8 percent were underweight before becoming pregnant. More than 25 percent were overweight, and 24.8 percent were obese.

While women with Asian-American descent under 20 years old, with college degree, pregnant for the first time and those who paid for their own delivery were the least likely to be overweight before becoming pregnant. Older women age more than 40 years were more likely to be obese before pregnancy.

Obesity prior to pregnancy also tend to occur in black, Alaska Native, or American Indian women and those who do not have a college degree and likely to depend on Medicaid to cover the expense for their delivery.

"This report provides descriptive information on prepregnancy BMI for births in 47 states and D.C. (96% of all births) occurring in 2014 and shows that approximately one-half of women were overweight or had obesity prior to becoming pregnant," the researchers reported.

"The birth certificate data can be used to fill a vital gap in describing and tracking BMI, specifically among childbearing women in the United States."

The results of the survey pose concern given the health implications of being obese and overweight during pregnancy.

Pregnant women who are overweight and obese are at increased risk for high blood pressure and diabetes, conditions that can lead to problems such as premature delivery and necessity to go through a cesarean section, which can further cause complications for both mother and child.

Women who are obese also have elevated risk for miscarriage compared with their counterparts who have normal weight. Babies born to overweight women are likewise at increased risk of suffering from birth defects such as neural tube defects and heart problems.

"Losing weight before you become pregnant is the best way to decrease the risk of problems caused by obesity," advised experts from the American Congress of Obstetricians and Gynecologists (ACOG).

"Losing even a small amount of weight (5-7% of your current weight, or about 10-20 pounds) can improve your overall health and pave the way for a healthier pregnancy."