Condottiere has mentioned everything (and more) that I have implemented in my campaign:
All team members were informed in advance that no children would be allowed to be born during the trip and everyone agreed to abide by this by signing their contract. Of course, everyone had the option of freezing sperm or eggs before departure.
On board, all crew members take contraceptives to rule out conception. In addition, there are routine monthly medical checks where pregnancy would be detected. If a pregnancy is detected, the embryo is removed and frozen. The mission guidelines state that such a child definitely will be born, but not during the mission.
However, the journey is not without its dangers and certainly there will be couples who would like to start a family afterwards. For these couples, there is the possibility that they can freeze a child, an embryo. Thanks to the latest genetic prediagnostics, the parents-to-be have the chance to have the later appearance of their child extrapolated on the basis of its genetic profile. This way, the parents can already build up a relationship with the child, even if it will be a long time before it can be born. There is a database on board where children are stored with their names and appearance. Should the parents die during the mission, the child is entitled to the pay that the parent saved up during the voyage.
Since everyone on my ship who wants to has access to anagathics, the chances of the crew members still being young enough to take on their parental role after the voyage are pretty good.
