|National Birth Defects Prevention Study (NBDPS) Notable Studies 2007–2012
Obesity as a Risk Factor for Birth Defects
Background: Persons are obese if their weight is greater than what is generally considered to be healthy for their height. Whether or not someone is obese is determined using their height and weight in a calculation called body mass index (BMI). In the United States, more than half of women aged 20 to 39 years are overweight (BMI from 25 to 29.9) or obese (BMI 30 or more). Previous studies have suggested that a woman’s BMI before pregnancy might affect her risk of having a baby with certain birth defects. NBDPS researchers looked at whether a mother’s weight before pregnancy was linked with an increased risk for 16 categories of major birth defects.
• This study confirmed that obese mothers are about twice as likely to have a baby affected by spina bifida than mothers who are a healthy weight (BMI between 18.5 and 24.9) at the start of pregnancy.
• Overweight and obese mothers also are at a slightly higher risk of having a baby affected by a congenital heart defect than mothers who are a healthy weight.
• Reaching and maintaining a healthy weight can help reduce these risks.
Waller DK, Shaw GM, Rasmussen SA, Hobbs CA, Canfield MA, Siega-Riz AM, Gallaway MS, Correa A. Prepregnancy obesity as a risk factor for structural birth defects. Archives of Pediatrics & Adolescent Medicine. 2007; 161(8):745-750.
Antidepressant Medications and Birth Defects
Background: Depression in women is most common during childbearing years. Selective serotonin-reuptake inhibitors, or SSRIs, are increasingly used to treat depression in pregnant women. Examples of medicines that are SSRIs include Prozac (fluoxetine), Zoloft (sertraline), and Paxil (paroxetine). We don’t know whether it is safe for pregnant women to use SSRIs, so NBDPS researchers looked for a possible link between taking these medicines during pregnancy and birth defects.
• SSRI use during pregnancy did not increase the risk for most birth defects studied, including heart defects. Overall, these results were reassuring.
• SSRIs were linked to a small increase in risk for three birth defects: anencephaly , craniosynostosis , and omphalocele , but these findings have not been confirmed in other studies.
• Women should talk with their doctor about the best options for management of their depression during pregnancy.
Alwan S, Reefhuis J, Rasmussen SA, Olney RS, Friedman JM. Use of selective serotonin-reuptake inhibitors in pregnancy and the risk of birth defects. New England Journal of Medicine. 2007; 356(26):2684-92.
Diet Quality and Neural Tube Defects (NTDs) and Orofacial Clefts
Background: In the past, single nutrients (such as the amount of each vitamin in the diet) have been studied to see if they affect a woman’s risk of having a child born with a birth defect. To expand beyond looking only at one vitamin or nutrient at a time, NBDPS researchers studied whether the overall quality of a woman’s diet is linked to a lower risk of some birth defects. For example, researchers scored women’s diet quality by looking at those who followed a Mediterranean diet consisting of a lot of fish, beans, and vegetables as well as those who followed the U.S. food guide pyramid.
Findings: Women with a healthier diet (women who received better scores in their diet quality) in the year before pregnancy had a lower risk of having a baby with either a neural tube defect (NTD), such as anencephaly and spina bifida, or cleft lip (with or without cleft palate).
Carmichael SL, Yang W, Feldkamp ML, Munger RG, Siega-Riz AM, Botto LD, Shaw G. Reduced Risks of Neural Tube Defects and Orofacial Clefts With Higher Diet Quality. Archives of Pediatrics and Adolescent Medicine. 2012; 166(2):121-126.
Cooking and Grilling By-Products as a Risk Factor for Gastroschisis
Background: Polycyclic aromatic hydrocarbons (PAHs) are chemicals that are released when fuel is burned or when meat is cooked or grilled. A link between exposure to PAHs during pregnancy and having babies born with gastroschisis has been found in animal studies, but not in studies of humans. Therefore, NBDPS researchers looked at this potential link in humans.
• Exposure at work to PAHs might increase the risk of having a baby with gastroschisis among mothers older than 20 years.
• Further study of this exposure and its potential link to birth defects is needed to confirm or refute this preliminary finding.
Lupo PJ, Langlois PH, Reefhuis J, Lawson CC, Symanski E, Desrosiers TA, Khodr ZG, Agopian AJ, Waters MA, Duwe KN, Finnell RH, Mitchell LE, Moore CA, Romitti PA, Shaw GM. Maternal occupational exposure to polycyclic aromatic hydrocarbons: effects on gastroschisis among offspring in the National Birth Defects Prevention Study. Environmental Health Perspectives. 2012; 120(6):910-915.
Folic Acid and Diabetes Associated Birth Defects
Background: Diabetes is a condition in which a person’s body cannot use the sugars and starches(carbohydrates) contained in foods to make energy. Previous studies have shown that women with poor control of diabetes (high or low blood sugar) during pregnancy have a higher risk of having a baby with a birth defect or other health problems. There can also be serious complications for the mother. NBDPS researchers examined whether or not taking vitamins containing folic acid (one of the B vitamins) before and during early pregnancy changed the risk of having a baby with a birth defect among women who already had diabetes.
• Babies born to mothers with diabetes who did not take a vitamin containing folic acid might be at increased risk for birth defects compared with babies born to mothers with preexisting diabetes who did take a vitamin containing folic acid before and during early pregnancy – meaning, the vitamin containing folic acid seems to help lower the risk of birth defects for women with diabetes.
• The findings in this study are only preliminary because there was a relatively small number of mothers who had diabetes before pregnancy that did not use vitamins or supplements that contained folic acid. In addition, we did not have information on how well these women kept their blood sugar within the healthy range (their level of diabetes control), which is an important factor that affects the risk of birth defects.
Correa AF, Gilboa SM, Botto LD, Moore CA, Hobbs CA, Cleves MA, Riehle-Colarusso TJ, Waller DK, Reece EA. Lack of periconceptional vitamins or supplements that contain folic acid and diabetes mellitus-associated birth defects. American Journal of Obstetrics and Gynecology. 2012; 206(3):218.e1-218e.13..
Neural Tube Defects (NTDs) and Folate Intake among Pregnancies Conceived after Folic Acid Fortification in the United States
Background: Previous studies have shown that women with diets high in folate, the natural form of the B vitamin, folic acid, have a lower risk of having a baby with a neural tube defect. There are two easy ways to be sure to get enough folate each day: take a vitamin that has folic acid in it or eat cereal grain foods containing folic acid. The addition of folic acid to cereal grains (like breads and breakfast cereals), known as folic acid fortification, was fully implemented in the United States by 1998. Each year folic acid fortification prevents about 1,000 neural tube defects (NTDs). Therefore, the occurrence of NTDs has decreased since the United States began fortifying foods with folic acid. In this study, NBDPS researchers looked at whether women’s intake of folic acid from both vitamin pills/supplements and from their diet affected the risk of NTDs after fortification was required in the United States.
• During the time of the study (1998 – 2003), which was after fortification of U.S. foods with folic acid had started, a mother’s risk of having a baby with a neural tube defect was not linked with the mother’s folic acid intake from either vitamin pills/supplements or from her diet.
• One possible explanation is that folic acid fortification prevented the NTDs that would have otherwise been caused by a lack of folic acid.
• Although folic acid fortification appears to benefit the majority of pregnant women in the United States, there might be some sub-populations, such as obese women or Hispanic women, who still have an increased risk of having a baby with a folic acid-preventable NTD.
• Further research is needed to study these sub-populations that may still have an increased risk.
Mosley BS, Cleves MA, Siega-Riz AM, Shaw GM, Canfield MA, Waller DK, Werler MM, Hobbs CA. Neural tube defects and maternal folate intake among pregnancies conceived after folic acid fortification in the United States. American Journal of Epidemiology. 2009; 169(1):9-17.
Exposures during a Father’s Job and Birth Defects
Background: Most birth defects are thought to be due to things that a woman comes into contact with, like the food she eats or the medicine she takes, just before or during her pregnancy. However, some things that the father comes into contact with before a baby is conceived might also affect the risk of having a baby with a birth defect, particularly if the exposure (for example, pesticides or paint fumes) affect the father’s sperm or fertility. Recently, NBDPS researchers looked at different exposures during work that might increase the risk of fathers having a baby with a birth defect. Investigators grouped hundreds of job types into many categories.
• The strongest link was seen between working as an artist and birth defects of the mouth, eyes, ears, digestive system, limbs, and heart.
• A father’s job as a photographer, photo processor, or motor vehicle operator might increase the risk for certain eye defects.
• Working as a landscaper or groundskeeper was linked with certain birth defects of the digestive system.
• These increased risks for certain jobs were relatively small and were based on small numbers.
• More studies are needed to understand which exposures for fathers might increase the risk of birth defects in their babies.
Carter TC, Olney RS, Mitchell AA, Romitti PA, Bell EM, Druschel CM, and the National Birth Defects Prevention Study. Maternal self-reported genital tract infections during pregnancy and the risk of selected birth defects. Birth Defects Res A Clin Mol Teratol. 2011 Feb;91(2):108-16.