Effects of hypothyroidism on pregnancy of rats

Adult female rats of approximately same age and weight were grouped and thyroidectomized before pregnancy and at different stages of gestation. While studying their pregnancy performances, it was observed that there was a significant (P less than 0.05) increase in the length of gestation in thyroidectomized animals as compared to intact controls. This is possibly due to the smaller litter size. The litter size and foetal weights were significantly (P less than 0.01) lower than the controls and were inversely proportional to the duration of the hypothyroidism during pregnancy. Hypothyroidism did not affect the implantation. The mammary gland growth was significantly (P less than 0.01) reduced in all the experimental groups. Hypothyroidism during pregnancy hardly affected the adrenal weight but significantly (P less than 0.01) decreased the ovarian weight possibly due to the disturbance in hypophysialgonadal axis.