THE INFLUENCE OF REMOVAL OF THE FETAL RAT BRAlN UPON INTRAUTERINE GROWTH OF THE FETUS AND THE PLACENTA AND ON GESTATION LENGTH

Abstract

Summary In order to study the influence of the fetal rat brain on the intrauterine growth of fetus and placenta, fetal and placental weights were first determined in control rats from day 17 up to day 21 of pregnancy; fetal weight appeared to increase in nearly linear fashion between days 17 and 21. Although placental weight increased steadily up to day 21, this increase was very small during the last days of pregnancy. Subsequently a simple technique was developed to aspirate the fetal rat brain in utero . A remarkable reduction of fetal growth was found on day 21 after fetal brain aspiration on day 18 or 19 of pregnancy. Placental weight appeared to remain static or even decreased after fetal brain aspiration on day 18 or day 19. The placental index increased after fetal brain aspiration. These effects, which appeared not to be caused by fetal blood loss, were similar to findings in pregnancies complicated by an anencephalic infant. Gestation length was not prolonged in rats treated by fetal brain aspiration, and the contraction phase started even earlier in rats who had fetal brain aspiration on day 19. Expulsion of the first fetus took place after the same gestation length in unaffected controls, sham‐operated rats and rats who had fetal brain aspiration.