During vaginal intercourse. A woman usually has to be "fertile" in order for her ovaries to be more accepting for a man's sperm. It's only when the man ejaculates you have the most likely chance of pregnancy occurring while he is inside of the woman. The spermicide "swim" in a sense towards her eggs. Not many get in at a time, usually only one or two at the most. But like most, spermicide can only survive in the female reproductive system for up to seven days, then they die out. The one[s] that got into the woman's ovary/ovaries will survive via the nutrients provided to them by her body. The rest of the nutrients will continue as the pregnancy progresses and the spermicide develops into fetuses/embryo.
I'm not sure this is 100% accurately worded, but this is what I remember from my text books during my Anatomy and Physiology courses. I hope this explained it to you!
I'm not sure this is 100% accurately worded, but this is what I remember from my text books during my Anatomy and Physiology courses. I hope this explained it to you!