Immuno-neutralization of maternal plasma oestradiol stimulates fetal growth in rats

On day 12 of pregnancy, 7 rats were injected with 2 ml of an anti-oestradiol antiserum a quantity capable of binding 2.4 micrograms oestradiol. Seven further (control) rats were injected with an antiserum raised against human serum globulin. After sacrifice on day 21 of pregnancy, the fetuses from treated rats showed an increase in both placental weight (0.851 +/- 0.023 g, n = 98 vs 0.752 +/- 0.019 g, n = 97) and fetal weight (4.446 +/- 0.426 g, n = 98 vs 3.403 +/- 0.211 g, n = 97). There was no significant difference in protein, DNA and RNA contents between the fetuses from treated mothers and those from control mothers. This experiment confirms that oestrogens may play a role in fetal weight gain.