Seasonal variation in spontaneous abortions.

Abstract

Using a national sample of hospital discharges, we found identical seasonal patterns for spontaneous abortions and conceptions but no significant seasonal variation in the rate of spontaneous abortions per 1,000 conceptions. The differences between our findings and those of previous investigators of spontaneous abortion may reflect our more comprehensive definition of spontaneous abortion, our more complete estimate of the monthly number of conceptions, and our more rigorous statistical analysis. The periodic regression analysis (PRA) reported in our study may be useful in other studies that monitor short-term trends.

Seasonal variation in conception and various pregnancy outcomes

“…Kaplan (1973) found a significant excess of spontaneous abortions during March through June. Warren et al (1980) found a significant seasonal pattern for the number of spontaneous abortions (above average from January through March and July and August), but the monthly rate of spontaneous abortions was not significant. In this study, we found no seasonal pattern for either the number or the rate of spontaneous abortions.…”

“…Kaplan (1973) and McDonald (1971) found an excess of spontaneous abortions in the spring (after controlling for conceptions) and suggested that infective agents that are epidemic in the spring may be the explanation. In contrast, Warren et al (1980) found no monthly excess of spontaneous abortions after controlling for conceptions. He and his colleagues concluded that the monthly number of spontaneous abortions is probably related to the seasonal pattern of conceptions.…”

“…He and his colleagues concluded that the monthly number of spontaneous abortions is probably related to the seasonal pattern of conceptions. In their analysis of induced abortion, Cohen and Bracken (1977) came to a conclusion similar to that of Warren et al (1980). The purpose of this study is to expand on the findings from these earlier studies by focusing on the question:…”

“…Several studies have suggested that in the United States conceptions have a seasonal pattern with the major peak in November and December (Kaplan, 1973;Cohen and Bracken, 1977;Warren, 1978;Warren et al, 1980;Seiver, 1985). Most of these studies make this point after analyzing the seasonality of live births (Warren, 1978;Seiver, 1985), live births and spontaneous abortions (Kaplan, 1973;Warren et al, 1980), or live births and induced abortions (Cohen and Bracken, 1977).…”

“…Most of these studies make this point after analyzing the seasonality of live births (Warren, 1978;Seiver, 1985), live births and spontaneous abortions (Kaplan, 1973;Warren et al, 1980), or live births and induced abortions (Cohen and Bracken, 1977). From these studies there is little question that conceptions follow a seasonal pattern; however, there is much debate as to the effect the conception pattern has on the individual seasonal patterns for various pregnancy outcomes.…”