University of wisconsin-madison

Stage 1 - Myometrial Contractions

The initial stage of parturition has been referred to as the preparative stage and is when myometrial contractions are start. The behavioral signs are:

  • restlessness, may get up and down
  • pawing at the floor or nest building
  • adominal pain (mare looks at her flanks), raise and switch tail, urinate
  • sweat patches in the flanks or elbows

During this stage of parturition the uterine contractions of the myometrium increase with intensity and frequency. Cervical dilation will occur as the foal and outer placental membrane (chorioallantois) push up against the cervix.

Once a mare is determined to be in stage 1, the tail should be wrapped and the perineal area scrubbed and dried. As the mare progresses in stage 1 she will often lie down and roll from side to side, stand up and then repeat the process. It is thought that this helps in the repositioning of the foal. During this stage of parturition the foal is on its back initially and rotates its front limbs and head around so that hoofs will be facing down during birth and the head will be between the legs (see dystocia for diagrams). As myometrial contractions continue, the cervix continues to dialate further. Evenually, the chorioallantois pushes through the cervix and ruptures. This is what is know as breaking of the water. Gallons of fluid will be released at this time. If the chorioallantois does not rupture, it will protrude from the vulva and apear with a velvety-red surface. This indicates premature placental separation and must be manually broken as the foal with oxygen deprived if it is not.

The breaking of the chorioallantois signals the end of stage 1 of parturition. Stage 1 may last from 30 minutes to 4 hours. In general, first time mare will be on the longer end while mares with previous parturitions (multiparous) will be on the shorter end.

Contraction in a Mare in Stage 1 of Labor

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