I think we have data for the amount of cosmic rays and other ionizing radiation flight crews are exposed to (
UNSCEAR 2000 report - Vol. II: Effects).
But how about actual statistics of birth rates (or if there's such a metric, problematic procreation like "can't get pregnant") in men and women of flight crews?
What guidance are you aware of? These days more and more women are seen in the cockpit, so I think the relative effects to men and to women are becoming more interesting.