Puerperium - Anatomy & Physiology

Introduction

• Immediately following parturition, the female enters a period of reproductive repair called the puerperium and begins lactation. For a period of time these two processes overlap.
• During the puerperium uterine involution and return to ovarian function occurs.
  • Involution is the reduction in size and remodelling of the endometrium so that the uterus can initiate and sustain another pregnancy.
• The time required for complete uterine involution and ovarian activity to resume varies among species.
• In many polyoestrous animals, the shortest possible puerperium is desirable because eligibility for a subsequent pregnancy is of high economic importance.

Myometrial Contraction and Expulsion of Lochia

• Myometrium undergoes strong, repeated contractions.
• The purpose of these contractions is:
  • Facilitate discharge of fluids and tissue debris from the uterus.
  • Compress the uterine vasculature and help minimize possibility of haemorrhage.
  • Reduce the overall size of the uterus.

• In most species, frequent post-partum suckling occurs and oxytocin is secreted.
• In suckled animals, uterine contractions occur on a frequent basis.
  • In dairy cows, the calf is usually removed 24 hours after parturition and milking takes place only 2-3 times a day.
    • Oxytocin episodes are reduced.
    • Myometrial contractions not as frequent
    • Delayed uterine involution
    • Delayed uterine involution limits fertility.

Reduction in Uterine Volume

• Immediately after parturition, the uterus undergoes rapid but highly coordinated atrophy.
• Uterine mass rapidly reduced to non-pregnant size.
• All species: marked size reduction in the first several days after parturition.
• Most species: myometrial contractions occur in 3-4 minute intervals for the first several postpartum days.
• Strong myometrial contractions subside within several days.

Lochia

• Shortly after parturition, a discharge called lochia is expelled from the vulva.
  • Lochia is a blood- tinged fluid containing remnants of the foetal placenta and endometrial tissue.
• Lochial discharge is normal in all species.
  • In dairy cows, lochial discharge occurs at day 2-9 postpartum.
    • Increase in blood and tissue debris in the lochia is normal, occurs day 5-10.
      • Due to sloughing of caruncular surfaces that leaves vascular 'stubs' that leak blood.
• Reduction of lochia in the uterus with myometrial contractions occuring for the first 7-10 days.
  • In dairy cows, up to 2000ml is expelled from the uterus in the first 2-3 days after parturition.
    • By 14-18 days, locial discharge is almost non-existent in most cows.