Neural tube defects in Victoria, Australia: potential contributing factorsand public health implications

Objectives: To measure population prevalence and determine potential predic tors of neural tube defects. Method: Analysis of all births reported to a mandated collection of perinat al data, and terminations prior to 20 weeks' gestation that have been repor ted to a data collection of birth defects in Victoria from 1983 to 1997. Pr evalence at birth and risk ratios of infant and maternal characteristics as sociated with neural tube defects were calculated. Results: Prevalence of spina bifida has remained steady for 15 years and wa s 8.8/10,000 in 1997. Anencephaly increased to 7.9/10,000 in 1997. After ex clusion of pregnancy terminations, the 1997 birth prevalence was 4.5/10,000 for spina bifida and 2.4/10,000 for anencephaly. Neural tube defects are i dentified in 1 in 1600 fetuses, the risk being significantly higher for epi leptic women (Adjusted Odds Ratio (AOR) = 3.70, 95% Cl 2.25-6.07), multiple births (AOR = 4.56, 95%Cl 3.46-6.02), teenage mothers (AOR = 1.47, 95% Cl 1.09-2.00) compared with those aged 25-29, and women with three or more pre vious pregnancies (AOR=1.40, 95% Cl 1.10-1.78). The risk was lower for wome n of East Asian (AOR=0.70, 95% Cl 0.49-1.00) and Middle Eastern origin (AOR =0.60, 95% Cl 0.35-1.02) and these differences were approaching statistical significance. Conclusion Total prevalence of neural tube defects did not decline up to 19 97. Implications: It is unlikely that targeting 'at risk' groups identified in this study would make a difference to neural tube defect incidence. How ever, consideration could be given to identifying larger 'at risk' groups s uch as those with homocysteine metabolism defects.