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Several birth defects surveillance systems have shown an upward trend in the birth prevalence of several congenital cardiovascular malformations. Improvements in clinical ascertainment have been suggested as an explanation for this increase. For several decades, 40-50% of infants with Down's syndrome have been reported to have cardiac defects associated with the unbalanced genotype. Therefore, secular changes in the frequency of ascertained cardiovascular malformations among infants with Down's syndrome in surveillance systems could shed light on improvements in the ascertainment of these defects. The authors examined changes in the frequency of ascertained cardiovascular malformations among 532 cases of Down's syndrome recorded in the Metropolitan Atlanta Congenital Defects Program from 1968 through 1989. Overall, 33% of the cases have reported cardiovascular malformations. However, the frequency of these defects in Down's syndrome infants increased dramatically from about 20% in the early 1970s to more than 50% in the late 1980s (p = 0.0001). This upward trend was seen for all major categories of cardiac defects and persisted after the cases were stratified by race, sex, maternal age, hospital of birth, birth weight, and gestational age. These results show improvement in the ascertainment of cardiovascular malformations among Down's syndrome infants in a surveillance population. They are also consistent with the hypothesis that the increasing rates of cardiac defects are related, at least in part, to improved ascertainment of these defects in the population.

Health care workers may be occupationally exposed to known and suspected teratogens including viruses, anesthetic gases, sterilants, mercury, and x-radiation. To assess the risk of congenital defects among offspring of health care workers, we analyzed parental occupational histories for 4,915 case babies with congenital defects, registered during the years 1968–1980 by the Metropolitan Atlanta Congenital Defects Program (MACDP) registry, and for 3,027 control babies born without defects during the same period. Offspring of mothers employed in a nursing occupation during the periconceptional period had a modest excess risk of having at least one congenital defect (relative risk [RR] = 1.42; 95% confidence interval [CI] 1.06–1.88); the offspring were at statistically significant increased risk of having anencephaly or spina bifida (RR = 2.00; 95% CI 1.01–4.30), coarctation of the aorta (RR = 2.06; 95% CI 1.10–3.82), genital system defects (RR = 1.61; 95% CI 1.03–2.53), and urinary system defects (RR = 3.43; 95% CI 1.41–8.34). These associations were not confounded by maternal age, education, or alcohol consumption. Offspring of mothers employed in administrative or clerical jobs in the health care industry also had a modest excess risk of defects (RR = 1.35; 95% CI 0.96–1.90), including a statistically significant excess risk of limb defects. We also found associations between neural tube defects and potential exposure to anesthetic gases and to x-radiation, but each association was based on only three case babies of potentially exposed parents. We found no associations between defects and paternal health care employment, except for a few individual defects, and these were based on small numbers of exposed subjects. Only one of five previous studies reviewed found an increased risk of congenital defects among offspring of nurses, but three of the four negative studies had substantially smaller sample sizes than the present study. Detection bias may be a possible explanation for the apparent excess risk of certain defects among offspring of nurses. © 1993 Wiley-Liss, Inc.1

Vitamins are essential to good health, yet the consumption of excessive amounts of some vitamins, particularly A and D, can lead to toxicity. In this issue of the Journal, Rothman et al.1 add to a body of evidence suggesting that the consumption of too much vitamin A by pregnant women may cause birth defects. On the other hand, the Public Health Service recommends that all women capable of becoming pregnant should consume 0.4 mg of folic acid daily to prevent the serious and common birth defects spina bifida and anencephaly.2–4 It is important for women and their physicians not . . .

Mortality rates (for blacks and whites only) in 24 cities with fluoridated and 22 with non-fluoridated water supplies in the United States were compared for the years 1969–1971. During these three years 570,671 deaths occurred in the cities with fluoridated water; the 1970 reference population in those cities was 15,972,817. The figures for the cities with non-fluoridated water were 351,053 and 11,106,746 respectively, so that the crude death rates for all causes were 1190.9 (fluoridated) and 1053.6 (non-fluoridated) per 100,000 person-years. Adjustments for age, sex and race reduced differences for some causes and removed them for others. Further correction, using analyses of covariance for city characteristics that influence mortality, gave adjusted death rates for all causes of 1123.9 and 1137.1, and for malignant neoplasms 195.3 and 196.9, in the cities with fluoridated and non-fluoridated water respectively. I found no evidence of a harmful effect of fluoridation. (N Engl J Med 298:1112–1116...

A retrospective epidemiological study of cleft lip and palate in King County, Washington, between 1956 and 1965 is reported. Multiple sources of ascertainment were employed, and particular attention was given to obtaining information concerning other associated malformations. Occurrences of cleft lip (CL), cleft lip and palate (CL + P), and cleft palate (CP) were analyzed by sepa rate categories, depending on the presence or absence of associated major or minor malformations. The results strongly indicated that clefts with associated malformations are different epidemiological entities from pure clefts. Sex-ratio reversals occurred for some categories with associated malformations. In contrast to the usual male excess of CL ± P, there was a female excess of CL ± P with major associated malformations. In contrast to the usual female excess of CP, 49% of children with CP with associated malformations were male. No maternal-age effect was observed for any “pure” cleft category, but significant “U-shaped” maternal-age distributions were seen for CL + P with associated major malformations, CP with associated major malformations, and CP with all associated malformations. Increased frequency of low birth weight and infant mortality were confined to categories with associated malformations. No significant birth order, season, secular change, or time–space clustering effects were observed. The incidence rate for all clefts was 1.84/1000 live births.

Relative to the countries of northern Europe, the United States has a high crude infant mortality rate. We compared the United States' fetal and infant mortality rates with those of Norway, a nation that is internationally recognized for having a low infant mortality. Norwegian birth-weight-specific rates were applied to the US birth populations, yielding adjusted rates. The adjusted rates, which are the crude rates that would have resulted in the United States if the Norwegian birth-weight-specific rates had been in force, were generally higher than the US rates that were actually observed. Thus, the major reason for the United States' poor international rank is probably its unfavorable birth-weight distributions, and any major improvement in the United States' international standing will likely await a reduction in the proportion of high-risk, low-weight births. (JAMA1982;247:987-991)

Since its biochemical characterisation in 19911 and its genetic identification in 1995,2 677C>T allele (T allele) of the 5,10 methylenetetrahydrofolate reductase ( MTHFR ) gene has been a focus of increasing interest from researchers world wide. The expanding spectrum of common conditions linked with the 677C>T allele now includes certain adverse birth outcomes (including birth defects), pregnancy complications, cancers, adult cardiovascular diseases, and psychiatric disorders.3–8 Although several of these associations remain unconfirmed or controversial,4 their scope is such that it becomes of interest to explore the geographical and ethnic distribution of the allele and associated genotypes.9 Accurate information on such distribution can contribute to studies of gene-disease associations (by providing reference population data) and population genetics (by highlighting geographical and ethnic variations suggestive of evolutionary pressures),10 as well as help to evaluate health impact (by allowing estimates of population attributable fraction). Current population data, however, show gaps and even for some ethnic groups or large geographical areas (for example, China) few data are available.3 Our aim was to supplement the available data by collecting a large and diverse sample of newborns from different geographical areas and ethnic groups, and to examine international variations in the distribution of the 677C>T allele. We present findings relating to more than 7000 newborns from 16 areas around the world. The study was conducted under the auspices of the International Clearinghouse for Birth Defect Monitoring Systems (ICBDMS) and was coordinated through its head office, the International Center on Birth Defects (ICBD). ### Sample selection Participating programmes, in consultation with the coordinating group, identified a population sampling approach that would be simple yet minimise sampling bias with respect to the MTHFR genotype. We made an explicit attempt to sample systematically the newborn population. Details of each programme’s approach are listed below, and further …