Preparation Calf rotates to upright position. Uterine contractions begin. Cervix begins to dilate, allowing water sac to protrude. 2 to 6 hours 2. Fetal Expulsion Cow usually lies down and fetal contractions begin.
Fetus enters birth canal.
Front feet and head protrude first. Calf is delivered. 1 hour or less 3. Uterine contractions expel membranes. Correct positioning of the calf as it enters the birth canal stimulates contractions of the diaphragm and straining of the abdominal muscles, which presses the head and feet of the calf against the cervix, causing it to relax and open.