Use of prostaglandin E1 analog (misoprostol) to aid cervical dilation in birth induction (a case report)

Abstract

The cervix is a barrier between the environment and the uterus, composed of longitudinal folds that continue along the uterine folds. Cervical dilation is associated with increased synthesis of prostaglandin E2 (PGE2). Dilatation may fail due to congenital malformations or adhesions of the cervix caused, for example, by previous dystocia or by failure of any mechanisms that regulate cervical relaxation including a reduction in collagen and glycosaminoglycans and an increase in water content and metalloproteinases. Labor induction often requires the ripening of the cervix mechanically or pharmacologically. Oxytocin success may be reduced if the cervix is not favorable or responsive. Misoprostol, a synthetic prostaglandin E1 analog, is widely used in reproduction in cases of oviduct obstruction. It also promotes cervical softening by the dissolution of extracellular collagen. A 17-year-old mixed-breed mare from a private farm in the Middle East presented with abdominal discomfort and signs of imminent delivery, 10th months after embryo transfer. A slight thickening of the uterus-placental junction (7.12mm) was observed during transrectal ultrasound evaluation, but there was no placental detachment. On transabdominal imaging, the absence of a fetal heartbeat, fetal movements, and torsion of the umbilical cord were observed. Imaging evaluations were performed with an ultrasound machine DCS - MyLab™25 GOLD, 5Hzfrequency. Hematological analysis of the mare showed results within normal ranges. Flunixin Meglumine (10mL i.v., Finadyne, 50mg/mL, MSD) was administered before the abortion procedure. After confirmation of fetal death and dystocia in the mare, the cervix dilation process began with a local application of 1mg of misoprostol 200mcg diluted in lubricating gel and mechanical massage. Then, intravenous oxytocin (Syntocin, 10UI/mL, Illium) was started gradually every 5 minutes (5IU, 5IU, 10IU, 10IU). Mild sedation and analgesia was achieved with detomidine (0.6mL i.v., Dormiun V, 10mg/mL, Agener Uniao) and butorphanol (1mL i.v., Torbugesic, 14,58mg/mL, Zoetis). The mare showed signs of delivery before the mechanical rupture of the allantochorion. The position of the fetus (head back and right shoulder flexion) was corrected transvaginally by mechanical maneuver. After removing the fetus, 5 mg of dinoprost (i.m., Lutalyse, 6.71mg/mL, Zoetis) was administered to aid uterine contractility and clearance. The placenta did not have macroscopic changes. The fetus showed an absence of the right posterior limb's first, second, and third phalanges. During fetal necropsy, no other changes were observed. Uterine lavage was performed 24h and 48h after the procedure, using Ringer Lactate Solution (LRS), with 10% iodine (20mL/5L LRS) followed by 20IU oxytocin every eight hours for two consecutive days.