Prevalence of neural tube defects in England prior to the mandatory fortification of non-wholemeal wheat flour with folic acid: a population-based cohort study.

Objectives: To determine the baseline trends in the total birth prevalence of neural tube defects (NTDs) in England (2000-2019) to enable the impact of folic acid fortification of non-wholemeal wheat flour to be monitored.
Design: Population-based, observational study using congenital anomaly (CA) registration data for England curated by the National Congenital Anomaly and Rare Disease Registration Service (NCARDRS).
Setting: Regions of England with active registration in the time period.
Participants: Babies that were liveborn or stillborn and pregnancies that resulted in a termination of pregnancy or a late miscarriage (20-23 weeks' gestation) with an NTD.
Main Outcome Measures: Total birth prevalence of anencephaly, spina bifida and all NTDs in England. Poisson regression analysis was used to evaluate time trends with regional register as a random effect. The progress of national registration across England was assessed.
Results: There were 4541 NTD pregnancies out of 3 637 842 births in England; 1982 anencephaly and 2127 spina bifida. NTD prevalence was 12.5 (95% CI 12.1 to 12.9) per 10 000 total births. NTD prevalence per 10 000 total births was significantly higher in 2015-2019 (13.6, 95% CI 12.9 to 14.4) compared with 2010-2014 (12.1, 95% CI 11.7 to 12.5). An increasing trend in NTDs overall was detected (incidence rate ratio (IRR) 1.01, 1.00 to 1.02), although further analysis determined this effect was confined to 2015-2019 (compared against 2000-2004, IRR 1.14, 1.04 to 1.24). The birth prevalence of anencephaly reflected this pattern. The prevalence of spina bifida remained relatively stable over time.
Conclusions: Baseline NTD prevalence for England has been established. National and standardised CA registration is in place, facilitating the systematic and consistent monitoring of pre-fortification and post-fortification NTD trends and evaluating the impact of fortification on NTD prevalence.
Competing Interests: Competing interests: None declared.
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