| Recent Findings
NBDPS researchers have over 200 project ideas and new topics are being added often. In 2009, 29 papers were published in medical and health journals. The results of some of these papers are discussed below.
Antibiotics and Birth Defects
During pregnancy, women can get more infections – germs that cause disease – because of all the changes in their bodies. So we were not surprised that the use of antibiotics – drugs that fight infections – goes up during pregnancy. Antibiotics were most often used during the fourth month of pregnancy.
We also looked at the link between antibiotics and birth defects. Antibiotics most used were penicillins, erythromycins, and cephalosporins. Generally, women who used these drugs did not show greater risk for birth defects. But we did see some links between the drugs sulfonamides (such as Bactrim) and nitrofurantoins (such as Macrobid) and birth defects. Women most often use these drugs for urinary tract infections. But we cannot be sure that the drugs caused the birth defects. It is very important to treat infections. Women should talk to their doctors about which antibiotics are safest to use during pregnancy.
Crider KS, Cleves, MA, Reefhuis, J, Berry, RJ, Hobbs, CA, Hu, DJ. Antibacterial medication use during pregnancy and risk of birth defects. Arch Pediatr Adolesc Med 2009;163(11):978-985.
Body Mass Index and Heart Defects
Body mass index (BMI) is a measure of body fat based on a person’s weight and height. Someone with a BMI reading of 25 or greater is considered “overweight” and someone with a BMI of 30 or greater is “obese.” In this study we looked at women who had a high BMI before becoming pregnant to see if they were at greater risk of having a baby with heart defects.
We found that women who were overweight or obese before becoming pregnant were at an increased risk for all types of heart defects. This link was strongest among women who also had gestational diabetes. This type of diabetes is first diagnosed in a pregnant woman. These findings stress the importance of being at a healthy weight before pregnancy.
Gilboa, SM, Correa, A, Botto, LD, Rasmussen, SA, Waller, KD, Hobbs, CA, Cleves, MA, Riehle-Colarusso, TJ. Association between prepregnancy body mass index and congenital heart defects. Am J Obstet Gynecol 2009 Sep 29. [Epub ahead of print]
Birth Defects and Sugar Intake
A mother’s nutrition plays a role in the complex causes of neural tube defects (NTDs), (birth defects of the brain and spinal cord). Much of the research has looked at folic acid intake, obesity, and diabetes. But other factors, such as eating a lot of sugar, may affect the risk for NTDs. When someone eats too much sugar, the glucose level, or the sugar in the body’s blood, becomes too high. The body makes insulin to take away some of that sugar. This is called “glycemic control.” Foods are given a “glycemic index value,” which shows how fast a food causes sugar levels in the blood to rise. A candy bar would have a much higher glycemic index value than broccoli.
We wanted to see if women who had diets high in sugar and foods with high glycemic index values were more likely to have babies with NTDs. An earlier study was done in California that showed a greater risk for NTDs in pregnant women who had this type of diet. However, our study using NBDPS data found there was no added risk of NTDs in babies whose mothers had a similar diet during pregnancy. More research needs to be done to find out why the California study and the NBDPS study did not have the same results.
Shaw GM, Carmichael SL, Laurent C, Siega-Riz AM. Periconceptional glycaemic load and intake of sugars and their association with neural tube defects in offspring. Paediatr Perinat Epidemiol 2008;22(6):514-9.
Craniosynostosis and Smoking
Craniosynostosis is a birth defect where some of the bones in a baby’s skull close too early. This changes the growth and shape of the head and face, and sometimes the brain. About 4 out of every 10,000 babies are born with this condition, and they often need surgery. Several studies suggested greater risk for this condition among babies born to women who smoked.
Using NBDPS data, we found that mothers who were heavy smokers during pregnancy (15 or more cigarettes per day) had an increased risk of having a baby with craniosynostosis. This risk is not seen when women quit smoking by early pregnancy. Also, we saw that women who did not smoke but were around cigarette smoke at home had an increased risk. This study adds to what we know about the effects of smoking during pregnancy.
Carmichael SL, Ma C, Rasmussen SA, Honein MA, Lammer EJ, Shaw GM. Craniosynostosis and maternal smoking. Birth Defects Res A Clin Mol Teratol 2008;82(2):78-85.
Genitourinary Infections and Gastroschisis
Genitourinary (reproductive and urinary organ) infections are common among sexually active women under 25. These include urinary tract and sexually transmitted infections. Chlamydia is a common infection and seems to be rising for these women. We also see a growing trend of babies born with gastroschisis to women 20 and younger.
We looked at the data to see if genitourinary infections increase the risk of having babies born with gastroschisis. Women who had these infections just before and during early pregnancy were 4 times more likely to have a baby with gastroschisis. Among the mothers who had babies with birth defects, 43% said chlamydia was the cause of their infection, compared to only 18% among the mothers who babies did not have birth defects. It is important for women to talk to their doctors and ask for a chlamydia test. (Chlamydia infections often do not show up on pap smears.) If the test result is positive, women should get proper treatment.
Feldkamp ML, Reefhuis J, Kucik J, et al. Case-control study of self reported genitourinary infections and risk of gastroschisis: findings from the national birth defects prevention study, 1997-2003. BMJ (Clinical research ed 2008;336(7658):1420-3.
Diabetes and Birth Defects
Women with diabetes are at increased risk for having a baby born with a birth defect. Women can have pre-existing (type 1 or type 2) diabetes or gestational diabetes (diagnosed during pregnancy).
NBDPS researchers wanted to know which types of birth defects were more common among mothers with diabetes. We found that pre-existing diabetes was more common among mothers of babies born with a range of birth defects. These include anencephaly, hydrocephaly, cleft lip with or without cleft palate, absent kidney, limb deficiencies, and over 10 types of heart defects. Mothers with gestational diabetes were often not at increased risk of having a baby born with a birth defect. But if the mother was overweight or obese and had pregnancy diabetes, the risk seemed to go up.
Correa A, Gilboa SM, Besser LM, et al. Diabetes mellitus and birth defects. American journal of obstetrics and gynecology 2008; 199(3): 237.e1-9. Epub 2008 Jul 31.
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