Reproductive factors, subfertility, and risk of neural tube defects: a case-control study based on the Oxford Record Linkage Study Register.

Periconceptual exposure to subfertility treatments is increasingly common, raising concerns about the possibility of malformations in the offspring. The authors conducted a case-control study to determine whether subfertility or its treatment was associated with increased risk of neural tube defects (NTDs). Cases were 694 women diagnosed with an NTD-affected pregnancy in Oxfordshire or West Berkshire, England, between 1970 and 1987. Cases were individually matched on maternal year of birth and year of index pregnancy to controls randomly selected from a computerized database. Data on demographic, reproductive, and obstetric factors were abstracted from patient hospital records. Overall, the period prevalences of subfertility and of subfertility treatment were 7% and 3%, respectively, No evidence was found that the risk of NTD-affected pregnancies was increased by either subfertility (odds ratio (OR) = 1.2, 95% confidence interval (CI): 0.7, 2.1) or its treatment (OR = 0.9, 95% CI: 0.4, 2.0). After adjustment, NTD-affected pregnancies were associated with female offspring (OR = 2.3, 95% CI: 1.8, 3.1), multiple birth (OR = 4.8, 95% CI: 1.2, 18.8), and higher numbers of pregnancies (p for trend = 0.005). The findings from this large, population-based study were wholly consistent with those from smaller studies that found no increased risk of NTD associated with exposure to fertility treatments but reported associations with various pregnancy outcomes.