Background: Achillea millefolium, (Asteraceae) is flowering plant which is popularly known as yarrow. It has been used in folk medicine to treat complaints such as inflammation, pain, wounds, hemorrhages and gastrointestinal disturbances. Objectives: To study the histological changes in uterus and reproductive hormones in female mice delivered to mothers treated with Achillea extract during pregnancy. Materials and Methods: Seventy pregnant female mice at age of six weeks were used as a model for this study. The animals were divided into two groups: control (C) (35), and experimental (G) (35) groups. The experimental group was given 1.5 mg/kg alcohol extract of Achillea millefolium dissolved in 1ml distilled water orally for the whole pregnancy, while the (C)was given distilled water only in the same amount and for the same period of time. The number and the body weight of the delivered offspring was recorded, in addition the endometrial thickness, the number and diameter of the uterine glands was measured in the histological sections at puberty. In addition evaluation of FSH, LH and E2 hormones levels were done. Results: The results of this study showed highly significant (p<0.01) decrease in the litter size of the experimental compared to the control group, as well as significant decrease (p<0.05) in the weight of the offspring, the endometrial thickness, the number and diameter of the uterine glands in the (G) compared to the (C). Conclusions: Consumption of low dose Achillea millefolium causes significant decrease in number and weight of the offspring, in addition to its effect on the uterus of the delivered female offspring.