Neural tube defects: is a decreasing prevalence associated with a decrease in severity?

OBJECTIVE

Severe neural tube defects (NTDs) tend to occur with disproportionate frequency in areas of high prevalence. The objective of our study was to determine the birth prevalence of NTDs during a 25-year period at a single institution based in an area of high prevalence for NTDs and to investigate if a decreasing prevalence resulted in a change in the type of NTDs.

STUDY

DESIGN

All cases of NTD affected births born at the Coombe Women's Hospital during the interval 1975-1999 were reviewed. There were 171,260 births at the Coombe Women's Hospital between 1975 and 1999. During this interval, there were 522 NTD affected births.

RESULTS

From 1975 until 1999 the prevalence of NTDs significantly decreased (P < 0.0001). This transition from high to low prevalence was associated with a significant decrease in severe forms of NTDs (P < 0.0001). This decreasing trend in rate and severity of NTD affected births was most dramatic prior to either food fortification or periconceptual folic acid supplementation.

CONCLUSIONS

Our transition from high to low prevalence for NTDs has been associated with a significant decrease in severe forms of NTDs.