['To investigate effects of a 5-day oral misoprostol regimen recommended for use in horses as a gastrointestinal mucosal cytoprotectant during colic on mid-gestation pregnancies.', 'To monitor cervical tone, ultrasonographic characteristics of the uterus, cervix and conceptus, as well as serum progesterone and oestrone sulphate concentrations, and observations of general health, behaviour and comfort of mid-gestation mares given a 5-day course of misoprostol or control treatment.', 'Eleven light horse and pony mares with known breeding dates were administered 5 µg/kg bwt misoprostol orally, twice daily for 5 days. General health and pregnancy status were monitored daily during treatment via general physical examination, as well as palpation and ultrasonography per rectum of the uterus, cervix and conceptus. Jugular serum was obtained during and for 5 days following treatment for assay of progesterone and oestrone sulphate concentrations. Additionally, daily 12 h video samples of the mares were obtained to evaluate behaviour and comfort.', 'All findings, including cervical tone, ultrasonographic characteristics of the uterus, cervix and conceptus, as well as progesterone and oestrone sulphate concentrations, and observations of general health, behaviour and comfort, were similar during misoprostol and control treatment.'] Is mid-gestation pregnancy disrupted by a 5-day gastrointestinal mucosal cytoprotectant oral regimen of misoprostol?