Why didn't the others do more regarding their pregnant women?

Since they had their submarine, why didn't they evacuate the
women to the mainland as soon as their pregnancies had advanced enough for them to be in danger? Why didn't they import large quantities of contraception? Why weren't more couples avoiding penetrative sex, at least when the woman was at her most fertile? In cases of people who were absolutely certain that they never planned to leave the Island, why didn't they take permanent measures to prevent pregnancies?