18 Sep 2026

What to Expect When You're Expecting: The Horse Edition

Having a mare in foal is one of the most exciting times for a thoroughbred breeder. From that first positive scan through to the foal finding its feet, here's what to expect across a Thoroughbred mare's pregnancy and foaling.

The First Checkpoint

Getting that positive scan is the moment every breeder is waiting for. This may come a few weeks after covering as the vet will scan the mare again. Mares normally carry their foals for somewhere between 320 and 360 days. 

Early Pregnancy: The First Couple of Months

In the early weeks, there's not a great deal to see on the outside of the mare. Pregnancy is typically confirmed around 14-16 days after a mare has ovulated, when pregnancy is visible using an ultrasound scanner as a small circular vesicle about 15mm in diameter. This scan is important for detection of twins, which if undetected, may result in the mare not going to full term. A follow-up scan at 25-30 days checks for a heartbeat. At this stage, a healthy mare doesn't need any change in management - normal feeding and exercise routines can simply continue as before. 

Mid-Pregnancy: Months Four to Eight

As the pregnancy progresses into the middle months, you'll start to notice gradual weight gain and abdominal enlargement. This is an important time to keep vaccinations and worming on schedule – your vet may recommend cover for Equine Herpesvirus (in the fifth, seventh and ninth month) and Rotavirus (in the eighth, ninth and tenth month of pregnancy), alongside flu and tetanus boosters.

The Final Stretch 
 
In the last couple of months, the foal roughly doubles in size, so it's worth keeping a close eye out for the signs that foaling is approaching. Typically 2–6 weeks out, the udder will start to develop – often referred to as "bagging up." Then, in the final 24–48 hours before birth, mares usually "wax up," with small drops of dried colostrum appearing on the teats. You may also notice the mare's belly dropping and a general relaxation through her body as she nears her time. 
 
Foaling
 
When labour begins in earnest, it tends to move quickly - once hard labour starts, delivery is usually complete within 20–30 minutes. It's well worth having your vet's contact details close at hand in case anything doesn't go to plan. For more support on what to expect and how to help through the foaling process, take a look at the TB-Ed course here.
 
Post-Birth 
 

Once the foal has arrived, it should be standing and nursing within a couple of hours. Getting colostrum into the foal early is vital – this antibody-rich first milk gives the foal the immune protection it needs from day one. The foal should also pass meconium (faeces accumulated whilst in utero) within the first few hours of life.

The placenta should be passed within around three hours; if it's retained beyond this, it's considered a veterinary emergency and needs prompt attention. Your vet will typically want to check over both mare and foal within the first 12–24 hours to make sure all is well.

TB-Ed also has a handy foaling checklist within its course – well worth a look before your mare's due date arrives.

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