NTD prevalences in central California before and after folic acid fortification.
BACKGROUND
In many regions, NTD prevalences were already declining prior to folic acid fortification. This study examined whether the declining prefortification (1989-1996) NTD prevalences continued into the postfortification period (1998-2003) in selected California counties.


METHODS
This population-based study used vital statistics data and birth defects registry data that were actively ascertained from medical records. The study population included all live births and stillbirths delivered in central California counties from 1989 to 2003. Cases included deliveries with NTDs during the same time period.


RESULTS
For all NTDs combined, the slopes indicated that NTD prevalence was decreasing by 7.5 (slope: -7.5; 95% CI: -12.4, -2.5) cases per 100,000 deliveries per year before fortification, whereas NTD prevalence was no longer decreasing after fortification. Comparison of the difference in the two slopes indicated that the postfortification slope exceeded the prefortification slope by 12.6 (95% CI: 2.6, 22.6) cases per 100,000 deliveries per year.


CONCLUSIONS
Annual NTD prevalences in central California did not continue to decrease after implementation of folic acid fortification.
Chen
Brian H
BH
March of Dimes Foundation, California Research Division, Oakland, California 94609, USA.
Carmichael
Suzan L
SL
Selvin
Steve
S
Abrams
Barbara
B
Shaw
Gary M
GM
D000328:Adult; D000757:Anencephaly / Q000453:epidemiology / Q000517:prevention & control; D002140:California; D005260:Female; D005492:Folic Acid / Q000627:therapeutic use*; D005500:Follow-Up Studies; D005527:Food, Fortified; D006801:Humans; D009436:Neural Tube Defects / Q000453:epidemiology* / Q000517:prevention & control*; D011247:Pregnancy; D011295:Prenatal Care / Q000379:methods; D015995:Prevalence; D016135:Spinal Dysraphism / Q000453:epidemiology / Q000517:prevention & control; D050497:Stillbirth / Q000453:epidemiology
D005492:Folic Acid