Whether they were "pagan women" inplies that they were grown and practicing some kind of religion that included idol worship before they were a part of Noah's family and I don't think that was true because of the mission God had planned out.
I think it is likely that Noah's sons were triplets.
GENESIS 5:
25 Methuselah lived one hundred and eighty-seven years, and begot Lamech. 26 After he begot Lamech, Methuselah lived seven hundred and eighty-two years, and had sons and daughters. 27 So all the days of Methuselah were nine hundred and sixty-nine years; and he died.
28 Lamech lived one hundred and eighty-two years, and had a son. 29 And he called his name Noah, saying, “This one will comfort us concerning our work and the toil of our hands, because of the ground which the LORD has cursed.” 30 After he begot Noah, Lamech lived five hundred and ninety-five years, and had sons and daughters. 31 So all the days of Lamech were seven hundred and seventy-seven years; and he died.
32 And Noah was five hundred years old, and Noah begot Shem, Ham, and Japheth.
The sons of Noah --
Japheth was the eldest -- Genesis 8:13.
Ham was the youngest -- Genesis 9:24.
This means Shem was the middle son.
Genesis 11:10 says Shem reached the age of 100 before he had his own son,
Arphaxad. That occurred two years after the Flood ended. Japheth was
born when Noah was 500. Shem was 100 years two years after the Flood
meaning he was born when Noah was 502 (round figures here). Ham was the
youngest. He came along sometime later.
Bob Schimmel