Looked at the Lutalyse label instructions.
The only thing it says is that if givien to a pregnant cow may cause abortion, (which is what one would want to do if he didn't want the cows bred). However, it also says that depending on the stage of the gestation amount of dosage required may vary. And in another part recommends not to give to animals over 100 days pregnant.
From past experiences, if an animal is pregnant and aborts, on occasion could be some retainage of the placenta.
Lutalyse is a good product, but as with anything there is that occasional risk, and one should use his own judgement.