This work aimed to study the effects of klimadynon® and 17β-estradiol administration on maternal rats and their postnatal day 21 young females in order to compare hormonal stimulation from each substance. Klimadynon® is a rhizome dry extract of Cimicifuga racemosa (CR BNO 1055 extract), the common name of this plant is black cohosh. The present study was carried out on eighteen pregnant rats weighing 170-250 gm and aged 16 weeks. The pregnant rats were arranged into three groups: control group, klimadynon group and 17β-estradiol. The klimadynon group was given daily oral dose of 33mg/rat/day,17β-estradiol group was given daily oral dose of 12.5 µg/rat/day, for an experimental period from 7 day of gestation and during lactation to postnatal day 21. The uteri of control and the two treatment groups of both mothers and their postnatal day 21 young were processed for histological examination, as well as morphometric analysis. The uterus sections of klimadynon group of mothers and their offspring showed no histological or morphometric changes. More severe lesions were apparent in uterus sections of rats treated with 17β-estradiol in the form of increase of  uterine layers thickness, extremely hypertrophy and hyperplasia of luminal epithelium cells, cellular anomalies, squamous metaplasia, cystic dilatation of endometrial glands, increase the thickness of uterine layers, increase in the number of endometrial glands and formation of papillary Endometrioid adenocarcinoma.