Introduction: Achillea (Asteraceae) is a plant that in recent years its anti-oxidant, anti-inflammatory, anti-spasmodic and anti-microbial qualities have been reported. Its extracts can also be used as a male contraceptive combination that has reversible effects too. The aim of this study is to examine the effects of the extract of this plant on the placenta and fertility.
 
Materials & methods: In this study, 40 female pregnant wistar rats were randomly placed in four equal groups which included one control and three experimental groups. Control group animals were treated with distilled water over 6-16 days. The experimental groups received Achillea plant extract in 200, 400, and 600 mg/kg concentration in the same timetable. Tissue specimens were collected then stained with H&E method and studied under light microscopy.
 
Findings: Results showed that the 400 and 600 mg/kg Achillea extract lead to sever placental congestion, elevation in the thickness of spongium of placenta, an increase in the number of the glycogenic cells and giant cells, elevation in the thickness of LIM of placenta as well as desidual thickness. Anatomical results showed a significant increase in the placental weight, diameter, thickness, index and a significant decrease in the fetal weight and length in treated animals that received the 400 and 600 mg/kg plant extract, compared with the treated animals which received 200 mg/kg plant extract.
 
Discussion & conclusions: According to result of this study, the injection of 400 and 600 mg/kg Achillea extracts leads to histological and histomorphometrical changes in the placenta tissue.