Well there are different places in the uterus where the embryo can attach. Ideally, you want the attachment to occur in one of the horns. This is common and gives the best outcome for the foal.
Now that you are aware of difficult births, it's a good time to prepare for them.
Difficult births occur, on average, around 13% of the time. Although, individual studs can experience difficulties up to 50% of the time.
You know what problems/symptoms to look for; the signs of foaling and what to put in your foaling kit to help you for the big moment and you've delivered your foal. This is just the start. Now you need to...