Anencephalus, Spina Bifida, and Hydrocephalus: Incidence Related to Sex, Race, and Season of Birth, and Incidence in Siblings

Neural tube defects in Gauteng, South Africa: Recurrence risks and associated factors

“…[19,20] The malformations most commonly observed were renal and cardiovascular defects, but there was significant variation in anomalies reported by different studies. [19,21,22] Earlier studies of siblings of individuals with NTDs failed to demonstrate an increased risk of other malformations; [2,12,23] however, more recent studies have found significant increases in the occurrence of apparently unassociated congenital abnormalities in siblings, with a variety of malformations being recorded, particularly in siblings of NTD patients with high spina bifida lesions. [19,24] …”

A Study of Temporal Variations in the Risk of Fetal Malformation and Death

“…Where only the denominator of the ratios had to be estimated, the numerators being "raw" frequencies (see Early Fetal Mortality, p. 1680), the estimators would make too little allowance for any abrupt, shortlived changes in the numbers at risk, hence the total amount of variation in the monthly ratios would be too large. Ingalls, 1953) have suggested that a community with large Jewish representation might be expected to have a relatively low incidence of CNS malformations, and that the frequency of anencephalus in particular has been reported to show wide geographical variation (Penrose, 1957 (Coffey and Jessup, 1959) suggested that an attack by this virus during pregnancy could double the risk of fetal OCTOBER, 1962 malformations as a whole. If the same risk factor* had applied to the New York victims of this epidemic, some associated excess of malformations would have been likely to show up in the present analysis, provided that about a quarter or more of the women pregnant during the epidemic were attacked.…”

Anencephaly and Spina bifida aperta

“…Seasonal variations have been reported for both anencephaly and spina bifida aperta in high-and low-risk areas [11][12][13][14][15][16], The majority of studies reporting seasonal trends for either defect have observed that an excess of affected births occurs during the winter months [11,[17][18][19][20][21][22][23], When date of LMP is used, or a gestational adjustment is made, the months at highest risk for conceiving infants with these defects appear to fall between March and August [20,24], In the majority of North American studies seasonality has not been well demonstrated for either defect [25][26][27][28][29].…”