Is my mare overdue?

By Jos Mottershead

One of the most commonly asked questions of the foaling season is "Is my mare overdue?". This is often precipitated by the misbelief that 340 or 341 days of pregnancy duration represent a "due date". Not so!

The average duration of gestation is anywhere between 320 and 370 days - so that mare which is at 345 days is not "overdue", but well within the normal range! The foaling date is picked by the foal who dictates that he or she is sufficiently developed and ready to be born, not by the mare who is watching the calendar on the wall!

Note too that the terms "premature", "dysmature" and "postmature" refer to the condition of the foal at birth and not to the gestational duration.

Here are some important facts to consider about gestational lengths: Some other important points for consideration:

It should be noted that if the mare is displaying severe signs of discomfort, she should be evaluated by a veterinarian. "Severe signs of discomfort" are not represented by a mare looking miserable, but rather by colic-like symptoms or extreme depression (no interest in feed, turnout, other animals etc.).

Induction of foaling simply because it is convenient for the mare owner, manager or veterinarian and not because of the presence of a medical problem with the foal or mare should be a crime that carries a mandatory life sentence! Induction of foaling results in a higher-than-normal number of dystocias (presentation problems), premature foals, and premature placental separations ("red bag" deliveries) than are seen with regular presentations. Do not induce foaling except in the face of a very clearly defined medical need, and only under strict veterinary supervision.

It is also important to note that while mammary gland development may be indicative of impending foaling (note that "waxing" is not a reliable indicator across the board, and other methods of prediction such as the one described in the article available by clicking here should be used), an absence of mammary development when in concert with prolonged gestation may be indicative of a problem with endophyte-infected fescue toxicity, and immediate veterinary involvement should be sought, as drug therapy (Domperidone) and other protocols (removal of the animal from the endophyte source) can be used to reverse the symptoms. Just to confuse the issue however, some mares do not show mammary development prior to foaling, and yet have not been exposed to endophyte-infected fescue!

Horses are not humans! They have different needs, and while the gestational period for humans is quite closely defined, there is a wide range of "normal" for the equine! Consequently, if you are reading this as a result of being concerned about your mares pregnancy duration, while we certainly encourage you to consult with your veterinarian to be on the safe side, you are, in all probability, merely losing sleep and worrying for no reason!
What was the duration in days of your mare's live-foal producing pregnancy?
Survey commenced in 2008 foaling season
Results © Equine-Reproduction.com

            319 Days or fewer
            320-326 Days
            327-332 Days
            333-338 Days
            339-344 Days
            345-350 Days
            351-356 Days
            357-362 Days
            363-370 Days
            371 Days or greater


© 2003 Jos Mottershead and Equine-Reproduction.com
Use of article permitted only upon receipt of required permission and with necessary accreditation.
Please contact us for further details of article use requirements. Other conditions may apply.

RETURN TO EQUINE REPRODUCTION ARTICLES MENU

1830364