Old Molly – Breeding

Tools and insight from covering to foaling — linked to Stable book.

Gestation calculator

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Chapter 1Day 0–19

A fertilised egg, smaller than a grain of sand, travels to the uterus and looks for its place.

Day 0–6
Conception & the journey to the uterus
Pregnancy begins. The egg is fertilised in the oviduct and the embryo reaches the uterus after 5–6 days.
Foetus size: about < 1 mm
Day 14–17
The embryo fixes & first scan
The embryo fixes in the uterus. This is the best window for the first ultrasound to confirm pregnancy and catch twins (which should be dealt with at once).
Day 16–19
Recommended first check
An important interval for catching problems early. The vet looks for uterine cysts that can be mistaken for the embryo.

Chapter 2Day 20–27

The embryo has settled and the placenta begins to form, ready to nourish it for eleven months.

Day 25
The placenta starts to form
Around day 25 the placenta begins to form so it can later nourish the foetus.

Chapter 3Day 28–39

A tiny, pulsing heart is now visible on the ultrasound. The embryo is about one centimetre long.

Day 28–30
Second pregnancy check
Time for a follow-up scan to see that the embryo is developing and that the heart is beating.
Foetus size: about 1 cm
Day 35
The umbilical cord forms
The foetus attaches to the uterine wall. Nutrients and oxygen now pass directly through the blood.
Day 36
Endometrial cups form
These produce the hormone eCG that helps maintain the pregnancy. It can be measured with a blood test (eCG test) between days 40–100.

Chapter 4Day 40–89

All major organs are in place and the most sensitive period is coming to an end.

Day 40
From embryo to foetus
The little one is now called a foetus. All the major organs are laid down.
Day 40–60
Risk of early embryonic loss eases
The most critical period is over, but stay alert. Stress and infection are common causes of problems.
ImportantFoetus size: about 7 cm

Chapter 5Day 90–179

Hooves, ears and sex take shape. The foetus grows from the size of a palm to a small cat.

Day 90
Third pregnancy check & the hooves
A recommended check. The hooves start to show on the foetus. It is now safe to take out foetal insurance.
Day 100–300
Oestrone sulphate test possible
A very reliable blood test. A positive result means the foetus is alive.
Day 120
Sex organs visible
You can often tell whether it will be a filly or a colt (with a skilled vet and scanner). The foetus is about the size of a small cat.
Foetus size: about 20 cm
Day 150
Risk of abortion
After day 150, loss of the foetus is called abortion. About 2–5% are affected. Watch for premature udder development.
Important

Chapter 6Day 180–329

The coat appears, and almost all growth happens in the final months. The mare needs more energy and protein.

Day 180
Halfway!
The foetus grows steadily. Keep up normal hoof care and sensible exercise.
Foetus size: about 60 cm
Day 210
Virus abortion (EHV-1) vaccination?
Many vaccinate in months 5, 7 and 9. Check with your vet what applies to you.
Day 240
The big growth spurt is near
The foetus is now about 80 cm long.
Foetus size: about 80 cm
Day 270
Increase the feed!
The greatest growth happens in the last four months. Raise energy and especially protein to avoid muscle loss in the mare and weak foals.
Day 300
About one month to go
The foetus is now large, about 120 cm. Start preparing the box, add straw and check cameras.
Foetus size: about 120 cm

Chapter 7Day 330–345

Most mares foal between day 330 and 345. The foal is often on its own legs within an hour.

Day 330
Foaling time
Most mares foal between days 330 and 345. The foal is now about 150 cm (nose to tail) and ready to meet the world!
Foetus size: about 150 cm

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Breeding

Tools and insight from covering to foaling — linked to Stable book.

Enter the covering date to build a detailed timeline for your mare.

When was the mare covered?