Plasma FSH was also elevated; however, there was no effect on pituitary FSH. These unequivocal results are likely due to the pulsatile secretion of LH and FSH. More meaningful results would require sequential blood sampling for LH and FSH.
Serova and Denisova reported that rats mated in hypogravity during spaceflight, indicating that female rats ovulated and cycled normally; however, no births resulted. Postflight laparotomies suggested that the fetuses were resorbed, but there is no clear indication of whether conception or implantation can proceed in the space environment. No systematic studies have examined the effect of spaceflight on early pregnancy. However, several spaceflight missions have included rat dams for varying durations between Days 9 and 19 of the 22-day gestation period.
The first spaceflight mission carrying pregnant mammals reported a reduction in pregnancy weight gain, prolonged parturition, lower birth weights, and increased perinatal mortality. Increased neonate mortality persisted into the F2 generation. Diet, housing, and other environmental conditions peculiar to this flight may have contributed to the adverse pregnancy outcomes. Another factor may have been stress; prenatal stress is associated with increased fetal mortality, abnormal nursing behavior, and increased postnatal mortality. However, subsequent spaceflight studies have yielded no evidence that pregnant rats are stressed during spaceflight.