The seasonal conception of lethal congenital malformations

Background. The objective of the study was to investigate the possibility o f the effect of seasonal temperature on the incidence of lethal congenital malformations in a retrospective study. Methods. At the National Institute of Perinatology in Mexico City, perinata l deaths due to congenital malformations were compared with the the remaind er of perinatal deaths over a period of 3 years in relation to the average temperature of the months in which the fifth week of gestation occurred. Results. The division between the average temperature of the individual mon ths was 18 degreesC, as there were no months with an average between 17.9 a nd 18.8 degreesC. An average of 0.86 perinatal deaths with lethal malformat ions had spent their embryonic life in a cold month, whereas an average of 1.54 had spent their embryonic life in a hot month; in contrast, an average of 10.24 perinatal deaths with lethal malformations had spent their embryo nic life in a cold month, and a smaller number (9.23) in a hot month. Conclusions. The perinatal deaths with lethal malformations therefore showe d a significant tendency to have spent their embryonic lives during the hot ter months in comparison with the other perinatal fetal deaths (p = 0.03). Further studies should be made with larger numbers of cases, maintaining ca reful attention to early perinatal data and local temperatures. (C) 2001 IM SS. Published by Elsevier Science Inc.