One in every 33 newborns in the United States is affected by birth defects. However, a recent study conducted by the Centers for Disease Control and Prevention highlights strategies to mitigate this risk.

The study identifies five key risk factors that can be addressed by public health officials or, in certain instances, by the women themselves: obesity, diabetes, exposure to smoking, food insecurity, and insufficient levels of folate, a crucial vitamin necessary for cell production.

The study reveals that 66% of women between the ages of 12 and 49 have at least one of these risk factors, with 10% having three or more. These findings by the CDC, shared in the American Journal of Preventive Medicine on Tuesday, draw from the responses of 5,374 women who took part in the National Health and Nutrition Examination Survey from 2007 to 2020.

“Highlighting these risk factors is vital to encouraging women to consult healthcare professionals if they have concerns or questions prior to pregnancy,” stated Arick Wang, a CDC health scientist and lead author of the study, in an email.

She further mentioned that risks can be reduced by actions like consuming the advised 400 micrograms (mcg) of folic acid daily, following a healthy diet and exercise routine, and regulating blood sugar levels.

According to CDC statistics, birth defects are the top cause of infant mortality. The risk factors often become significant before some women realize they are pregnant. While the precise causes of birth defects remain largely unknown, there is a consensus among scientists that they result from the interplay of genetic, environmental, and lifestyle factors.

“This should be a wake up call to all of us,” said Dr. Michael Warren, chief medical and health officer of March of Dimes, a nonprofit research and advocacy group focused on maternal and infant health.

“We want to make sure that people have access to nutritious foods,” said Warren, who wasn’t involved in the study. “We want to make sure that people have safe places to be physically active.”

People with food insecurity can be deficient in nutrients that are vital for a fetus’ organs to develop properly, including folate. For instance, low concentrations of folate in the blood are associated with neural tube defects — brain or spine defects that develop in the first month of pregnancy. Doctors recommend that people who are pregnant or trying to get pregnant take folic acid, the synthetic version of folate.

Since 1998, the Food and Drug ministration has required that enriched cereal-grain products be fortified with folic acid. Wang, the CDC scientist, said in a press release that the policy likely prevents more than 1,300 babies each year from being born without neural tube defects.

“The vast majority of birth defects that occur, we still don’t know why they occur,” Nembhard said. “Even when women do everything right — they don’t smoke, they don’t drink during pregnancy, they monitor caffeine intake, they exercise — you can still have an outcome that is not what you wanted.”

Warren, who until June served as associate administrator of HHS’ Maternal and Child Health Bureau, said many women might not be aware that conditions like obesity and food insecurity are also risk factors.

Obesity, which affected roughly one-third of the women surveyed, was the most common modifiable risk factor in the CDC study. Scientists aren’t exactly clear on why it’s linked to birth defects, but they suspect it has something to do with changes to a woman’s metabolism — such as the way her body manages insulin and glucose — that may lead to abnormal development in the fetus.

“When [our] cells are growing and forming organs, we really rely on everything to be working just as it should. And when you disrupt those processes, things can go awry,” Warren said.

High blood sugar from diabetes may also lead to abnormal organ development, he said. And some of the chemicals in cigarette smoke, including nicotine, can reduce the supply of oxygen to the fetus.

Warren said there’s more to be done. He pointed to Mississippi, which declared a public health emergency last week over its high infant mortality rates and pledged to eliminate “care deserts,” where women don’t have access to obstetricians.

Outside researchers lauded the study’s release amid layoffs and proposed funding cuts to the agency.

“We’re delighted that this study has been ongoing. There were some questions about whether or not it would continue,” said Wendy Nembhard, director of the Arkansas Center for Birth Defects Research and Prevention at the University of Arkansas for Medical Sciences.

The Department of Health and Human Services in March announced the termination of 2,400 CDC employees. However, a federal judge issued a preliminary ruling on Aug. 12 that blocked the layoffs for certain CDC programs, including the National Center on Birth Defects and Developmental Disabilities — the group behind the new study. At least 600 CDC employees are still expected to receive permanent termination notices.