Talk:Abnormal Development - Anencephaly

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Cite this page: Hill, M.A. (2020, January 25) Embryology Abnormal Development - Anencephaly. Retrieved from


Neural tube defects: Sex ratio changes after fortification with folic acid

PLoS One. 2018 Mar 14;13(3):e0193127. doi: 10.1371/journal.pone.0193127. eCollection 2018.

Poletta FA1,2, Rittler M3, Saleme C4, Campaña H1, Gili JA1, Pawluk MS1, Gimenez LG1, Cosentino VR1, Castilla EE1,2, López-Camelo JS1,2.


BACKGROUND: Historically, neural tube defects (NTDs) have predominated in female infants but the reasons remain unclear. In South America, the pre- folic acid fortification (FAF) rates of NTDs were around 18/10,000 births for females and 12/10,000 births for males, with an estimated sex ratio (male/female) of 0.67. During the post- FAF period, unpublished routine reports have indicated changes in the sex ratio for these defects while some descriptive reports are controversial. To date and to our knowledge, however, no studies specifically focusing on these changes to test this hypothesis directly have been undertaken. The aim of this study was to analyze changes in the sex ratio of infants with NTDs after FAF in South American countries. MATERIALS AND METHODS: With a descriptive cross-sectional study design, 2,597 infants with isolated NTDs born between 1990 and 2013 in 3 countries participating in the Latin American Collaborative Study of Congenital Malformations (ECLAMC) network were included: (Chile N = 521 and Argentina N = 1,619 [with FAF policies]; Venezuela N = 457 [without FAF policies; used as control]; total births = 2,229,561). The differences-in-differences method and Poisson regressions were used to evaluate the sex ratio shift from female to male before vs. after FAF, and to assess whether these differences were related to the fortification. RESULTS AND CONCLUSIONS: In Chile and Argentina the prevalence of NTDs, particularly anencephaly and cervico-thoracic spina bifida, showed a greater reduction rate in females than in males after FAF, resulting in a change of the sex ratio of infants with NTDs. Some mechanisms possibly involved in this differential reduction are proposed which might be useful to identify the pathogenesis of NTDs as a whole and specifically of those susceptible to the protective effect of folic acid. PMID: 29538416 PMCID: PMC5851584 DOI: 10.1371/journal.pone.0193127


Sex ratios among infants with birth defects, National Birth Defects Prevention Study, 1997-2009

Am J Med Genet A. 2015 May;167A(5):1071-81. doi: 10.1002/ajmg.a.36865. Epub 2015 Feb 25.

Michalski AM1, Richardson SD, Browne ML, Carmichael SL, Canfield MA, VanZutphen AR, Anderka MT, Marshall EG, Druschel CM.


A small number of population-based studies have examined sex differences among infants with birth defects. This study presents estimates of sex ratio for both isolated cases and those with multiple congenital anomalies, as well as by race/ethnicity. Male-female sex ratios and their 95% confidence intervals were calculated for 25,952 clinically reviewed case infants included in the National Birth Defects Prevention Study (1997-2009), a large population-based case-control study of birth defects. The highest elevations in sex ratios (i.e., male preponderance) among isolated non-cardiac defects were for craniosynostosis (2.12), cleft lip with cleft palate (2.01), and cleft lip without cleft palate (1.78); the lowest sex ratios (female preponderance) were for choanal atresia (0.45), cloacal exstrophy (0.46), and holoprosencephaly (0.64). Among isolated cardiac defects, the highest sex ratios were for aortic stenosis (2.88), coarctation of the aorta (2.51), and d-transposition of the great arteries (2.34); the lowest were multiple ventricular septal defects (0.52), truncus arteriosus (0.63), and heterotaxia with congenital heart defect (0.64). Differences were observed by race/ethnicity for some but not for most types of birth defects. The sex differences we observed for specific defects, between those with isolated versus multiple defects, as well as by race/ethnicity, demonstrate patterns that may suggest etiology and improve classification. KEYWORDS: birth defects; race/ethnicity; sex ratio PMID: 25711982 DOI: 10.1002/ajmg.a.36865