What you see. The starting point for addressing any equine health related issue is your observation.


Udder Enlarged in Pregnant Mare, Seems too Early


Udder enlargement is the result of hormonal signaling from the maturing fetus and placenta, toward the end of gestation. If this signaling occurs too soon, then udder enlargement will be premature. In most cases, udder enlargement begins about 4-6 weeks prior to the predicted foaling date, or at about 280 days.

Different mares have different patterns of udder development, but generally, the udder begins to enlarge at about 4-6 weeks prior to the foaling date. In most mares, the udder gradually enlarges up until about 2 weeks prior to birth. Usually there is a significant increase in size of the udder then, followed by a final increase right before foaling.

In the final days before foaling, the teats become tight and swollen with fluid. At no time should there be significant dripping of milk from the teats. Premature lactation is a potential emergency because it indicates impending foaling. For normal immunity, the foal will need every bit of colostrum (first milk) that the mare has produced.

If udder development occurs too early (before 270 days gestation) or this is accompanied by dripping of milk it may be an indication of a problem with the fetus or placenta and impending foaling. So this is an emergency.

  • Code Red

    Call Your Vet Immediately, Even Outside Business Hours
    • If the results of the Whole Horse Exam (WHE) in the resting horse indicate fever (Temp>101F/38.3C) or heart rate greater than 48 BPM.
    • Milk is dripping from the teats, in addition to this sign.
  • Code Orange

    Call Your Vet at Their First Available Office Hours
    • If the results of the Whole Horse Exam (WHE) suggest the horse is otherwise normal.

your role


What To Do

Assess the horse's general health using the Whole Horse Exam (WHE) on the Late-Term Pregnant Mare, paying particular attention to the presence or absence of vaginal discharge or dripping milk. Consider the mare's attitude, appetite and rectal temperature.

Double check the mare's breeding dates before you call your vet. Then contact your vet with these dates, as well as your findings and concerns.

your vet's role

Your vet might recommend that they examine the mare in attempt to identify the problem and give you the options for managing it. This involves physical exam, and assessment of the pregnancy, fetus and placenta.
Questions Your Vet Might Ask:
  • What were the mare's breeding dates?
  • Have you noticed vaginal discharge?
  • Does the udder have milk in it?
  • What are the results of the Whole Horse Exam (WHE)?

further reading & resources

Author: Doug Thal DVM Dipl. ABVP