Obesity and Birth Defects

Worries about birth defects in the past have usually been directed at alcohol, drug abuse, medications (thalidomide in the late 1950s, acne drug Accutane in the -90s) and environmental pollutants. Its clear to most pregnant mothers that substances which have little to no effect on adults are able to inflict devastating alterations on a fetus.

But recently, the scientists at the University of Texas sounded the alarm bells about something else: in an interview reliant study (1) they found that mothers who were considered obese at the time of conception were at heightened risk for giving birth to infants suffering from the birth defect known as spina bifida.

In addition to the foregoing, other birth defects affecting the male genitalia as well as the intestinal tracts of both genders were also noted. In some cases there were visible signs of abnormality, such as a marked decrease of digit length with respect to fingers but also toes.

Cause and Effect?

Researchers are very careful, however, to point out that causation for the birth defects could not readily be identified; instead, the only fact that could be proven was the relationship between a heightened risk of birth defects in infants born to women who were obese at the onset or duration of the pregnancy. Questions caused by these findings abound, of course, and women are unsure just exactly what to do with this data.

Considering the firestorm of questions and the lack of answers, the researchers have made tentative guesses as to the relationship that exists between obesity and the presentation of birth defects:

 Obesity and Birth Defects

1. First and foremost was the suggestion that obese mothers may not be making healthy food choices. In other words, failure to ingest a healthy diet that takes a balanced approach to the intake of proteins, carbohydrates, fats, fiber and a host of other nutrients may quite possibly be to blame for the birth defects which are being seen. It is well known that spina bifida (2) is directly related to a lack of folic acid in the diet, and while this may be supplemented once a pregnancy is diagnosed, the sad reality dictates that the first few weeks and months which are the most crucial in the development of the fetus usually go by without the woman even realizing she is pregnant and needs to supplement her diet. Thus, when folic acid is finally supplemented, it might be too little too late.

2. Obesity is quite often the springboard for a host of other health issues, many of which may remain undiagnosed for a long period of time. If an expectant mother is obese and this condition has led to the development of diabetes, the possibility of the undiagnosed and untreated condition affecting the fetus is present.

3. Unhealthy habits of obese women are legion, but perhaps the most dangerous ones relate to diet efforts (3). How many overweight women will purchase over the counter diet pills and Internet prescription knock-offs for sometimes dangerous diet materials? How many binge and purge? These behaviors, when they occur during pregnancy, are not only endangering the mothers health but also the childs. If you consider that a pregnancy usually is not noticed for a few weeks, it is not surprising to note that for the first few weeks of life, the fetus is subjected to the chemicals the mother is ingesting in an effort to lose weight. Birth defects are a serious danger in this situation.

Greater Risk of Hyperactive Children

Another study adding to the evidence that obesity and pregnancy do not mix well is a study (4) from Uppsala University in Sweden, which found that if a woman is overweight when she becomes pregnant, there is a much greater that her child will have ADHD-like symptoms when he/she reaches school age.

More than 12,500 children in Sweden, Finland, and Denmark were monitored from their time in the womb up to school age, when their teachers were asked to answer a questionnaire about the childs behavior. Roughly one out of ten children had marked difficulties with their attention span and with hyperactivity.

The correlation between mothers body mass index and child symptoms was found not only in those cases where the mother suffered from pronounced obesity but also in cases where the women were moderately overweight.

Expectant mothers who were already overweight and moreover gained a considerable amount of weight during the course of the pregnancy ran a greater risk of having a child who would later show signs of ADHD than did women of normal weight who experienced the same weight gain during pregnancy.

“It is important that women start off pregnancy at an optimal body weight. It has been well documented in recent years that mothers overweight is associated with increase risk for a number of complications both to herself and to her child. Our results could be yet another problem to add to the list. But it is not good to be extremely thin either,” says Alina Rodriguez, lead author of the study.


1. D. Kim Waller, Prepregnancy Obesity as a Risk Factor for Structural Birth Defects Arch Pediatr Adolesc Med. 2007;161:745-750. Full Text

2. Shaw GM, Velie EM, Schaffer D. Risk of neural tube defect-affected pregnancies among obese women. JAMA. 1996;275(14):1093-1096.

3. Carmichael SL, Shaw GM, Schaffer DM, Laurent C, Selvin S. Dieting behaviors and risk of neural tube defects. Am J Epidemiol. 2003;158(12):1127-1131 Full Text

4. A Rodriguez, J Miettunen, T B Henriksen, et. al. Maternal adiposity prior to pregnancy is associated with ADHD symptoms in offspring: evidence from three prospective pregnancy cohorts
International Journal of Obesity advance online publication 16 October 2007; doi: 10.1038/sj.ijo.0803741

Image. Chris Nurse, Wellcome Images Creative Commons.