First, they should consider their own age and career stage. It's best to wait until they have finished university and are at a good point in their careers to take parental leave. On the other hand, women's fertility declines through their 30s and there is some evidence that older fathers are correlated with a higher rate of birth defects. Next, the couple should have been together for long enough to ensure the relationship is stable and be committed to staying together until the children reach university. Next, both parents should have genetic testing to avoid passing on hereditary diseases