I know a little only because a friend and neighbor had a small herd of registered minnies and stallion. When it was time , the stallion was introduced to a mare once or twice during the heat cycle. Then everyone was separated until the next cycling period.
Breeding is one of those areas that seem especially complex to me with so many variables!
I haven’t been on the pregnancy and foaling thread, but perhaps your question posted there would be seen by those who do breed?