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.