Previous study made with Rosmarinus officinalis Linné aqueous extract (rosemary) demonstrated that 130 mgkg-1 dose, commonly used as abortive by women, given to pregnant rats during preimplantation period may interfere with embryo implantation, but not disrupt the normal development of conceptus when this extract was given after implantation. The objetive of this study was to verify the mechanism by which a rosemary aqueous extract influences embryo implantation, by correlating its ingestion with possible alterations in embryo development.

Pregnant wistar rats were randomly distribuited to 3 groups:

one control (water) and 2 experimental groups.

The rosemary extract was administered in 2 doses:

260 and 1040 mgkg-1, p.o., to females from GD1 (gestation day 1) to GD4, once daily. Then, each groups was subdivided and killed at 2 different moments: half of the animals at GD5 and the other at GD21, respectively for evaluation of the blastocysts before implantation, and for fetal evaluation. The treatment with 260 mgkg-1 caused a significant increase in the number of anomalous embryos collected in the uterus at GD5, presenting an embryotoxic effect. However, the embryos that managed to implant presented normal development when observed at term of pregnancy due to the absence of anomalies in the fetuses and no increase in the postimplantation loss rate. The administration of 1040 mgkg-1 of the extract did not present any embryotoxic effect. Nevertheless, at GD5, a decrease of 40 percent in the number of blastocysts present in the uterus was observed. This fact suggest that the treatment with the highest dose caused a longer embyo retention in the oviduct. Therefore, further studies are needed to determine the constituents of rosemary that are responsible for its embryotoxic effect and delayed embryo arrival at the uterus. Since rosemary is widely used in food preparations, it is important to realize more studies to determine the constituents that are responsible for the effects of rosemary aqueous extract.