Swallowing

Science now knows that when pregnant women orally ingest the ejaculate of the father of the child she bears, she has a SIGNIFICANTLY reduced chance of developing preeclampsia. Further research has also found that the regular ingestion of the ejaculate of her partner can help a woman become pregnant in the first place. It introduces the partners proteins into her system as a whole, and gradually acclimates her system to the presence of his proteins, so that she is far less likely to have an immune response when the fertilized egg attempts to implant, increasing the chance of successful pregnancy.

Of course, I didn't fucking KNOW THIS ten years ago, or my wife's pregnancy would have been MUCH more fun for me. (She didn't actually have preecampsia, so the effect on her would have been minimal, but trying to prevent it would have been a blast. Health first!) :-)