Chernobyl fallout and outcome of pregnancy in Finland

Possible effects of Chernobly fallout on outcome of pregnancy in Finland we re evaluated in a nationwide follow-up study. The outcomes were the rate of live births and stillbirths, pregnancy loss, and induced abortions by muni cipality. Exposure was assessed based on nationwide surveys of radiation do se rare from the Chernobyl fallout, from both external and internal exposur es. Using these measurements, we estimated the monthly dose rate for each o f the 455 Finnish municipalities. On average, the dose rate from Chernobyl fallout reached 50 mu Sv per month in May 1986-a doubling of the natural ba ckground radiation. In the most heavily affected area, 4 times the normal b ackground dose rates were recorded. Given the underlying: regional differen ces in live birth, stillbirth, and abortion rates, we used longitudinal ana lysis comparing changes over time within municipalities. A temporary declin e in the live birth rate had already begun before 1986, with no clear relat ionship to the level of fallout. A statistically significant increase in sp ontaneous abortions with dose of radiation was observed. No marked changes in induced abortions or stillbirths were observed. The decrease in the live birth rate is probably not a biological effect of radiation, but more like ly related to public concerns of the fallout. The effect on spontaneous abo rtions should be interpreted with caution, because of potential bias or con founding. Further, there is little support in the epidemiologic literature on effects of very low doses of radiation on pregnancy outcome.