The Effect of a Single Dose of Stilboestrol on Cervical Dilation in Pregnant Sheep

Abstract

Radio telemetric recordings of intra-uterine pressure changes were carried out in ewes during the last 2 to 3 weeks of pregnancy. Observations were made on 6 normal ewes to add to the data from a control series reported previously. A single dose of 20 mg. stilboestrol was injected into 14 ewes, either in mid-pregnancy or within 2 weeks of term. Of these, 4 ewes developed a riug-womb-like condition and the cervix had to be dilated manually; 2 developed a genuine ring-womb and had to be sectioned. All had had labours of at least twice the control span and the intra-utcrine pressure waves recorded were indistinguishable from those in the control series. Sondes inserted through the cervix in 2 experimental ewes and in 13 clinical ring-womb cases after therupture of the amniotic sac are not considered to give a true refection of pressures impinging on the cervix to bring about dilation. It is concluded, tentatively, that ring-womb is primarily a disorder of the cervix and that the naturally occurring condition may be hormonal in origin.