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What did you look at during the initial investigation?
We compared information from prenatal records and hospital discharge records of women who had a pregnancy affected by a neural tube defect and women who had healthy pregnancies during the same time period. We looked at several risk factors for neural tube defects including, but not limited to, documentation of folic acid use (including prenatal vitamins), pre-pregnancy weight, family history of neural tube defects, and health risk behaviors of the mother during pregnancy. We also looked at the source of home drinking water.
What did you find?
We were unable to find any significant differences between women who had pregnancies affected by a neural tube defect and those with healthy pregnancies. We noted that all women in the investigation had low early pregnancy folic acid use. We used data we collect on recently pregnant women statewide to compare folic acid use in early pregnancy in this three-county area with the rest of the state. For 2009-2011, about 61 percent of survey respondents in the three-county area compared with about 50 percent of respondents from the rest of Washington did not take a multivitamin, prenatal vitamin, or folic acid vitamin at all in the month before they got pregnant.
Is it common not to find anything?
Unfortunately, in these types of investigations, it is common to find no particular risk factor that stands out as the most likely explanation for a high rate. Even though the rate of neural tube defects in the three-county area is high, the total number of cases is small in terms of numbers needed to identify causes of these birth defects.
What do the results mean?
Although the number of affected pregnancies was large for the three-county area, even larger numbers are often needed to identify potential causes. The investigation has been based on medical records review and medical records may not capture all the needed information. We continue tracking cases of neural tube defects in the area looking for reasons for the higher rate.
Did you look at anything besides medical records?
We determined the source of drinking water based on address. We found no differences between affected pregnancies and healthy pregnancies based on whether an address was served by a public water supply or private well; 77 percent of cases were on public water supplies.