From: Rabbi Moshe Sofer
To: Rabbi Avraham
A husband sought to claim a shtar chatzi zachar from his father-in-law's estate, arguing his son had inherited it from his mother before dying within thirty days. The Chasam Sofer rules that since the infant was never examined for signs of viability, it is a safek nefel, and the grandfather's heirs retain their chezkas mamon. He rejects the Pri Megadim's position that the majority principle (most births are viable) can be used to extract money, holding that this majority is weakened by the common occurrence of non-viable births and is in any case undermined by the child's actual death.
Source: Shu"t Chasam Sofer EH II §161