CONGENITAL DEFECTS IN GUINEA PIGS - PRENATAL RETARDATION OF BRAIN GROWTH OF GUINEA PIGS FOLLOWING HYPERTHERMIA DURING GESTATION

Hyperthermia was induced in pregnant guinea pigs for 1 hour on 2, 4, or 8 consecutive days between days 4 and 67 of gestation. Mean newborn brainweight was reduced substantially and incidence of micrencephaly increased following hyperthermia on 4 or 8 successive days during days 15 to 32, and apparently to a lesser degree following exposure on days 39 to 46, and 53 to 60 of gestation. Maternal hyperthermia at other than these periods was associated with little or no reduction in mean brainweight or increase in incidence of micrencephaly. Following hyperthermia on 2 successive days during days 14 to 31 of gestation the incidence of micrencephaly was increased and mean brainweight decreased in offspring from females heat stressed on days 16–17, 20–21, 22–23, and 24–25. The effects of hyperthermia on brain growth were most marked on days 20–21 or 22–23. Following 1 hour of maternal heat stress on day 21 of gestation, brainweight of newborn animals was reduced if maternal body temperature was elevated more than 2.5°C above normal. For each 1°C elevation in body temperature above this level brainweight was reduced by approximately 8.4% compared with control values. Copyright © 1969 Wiley‐Liss, Inc., A Wiley Company