ביאור מונח "הזרעת הבעל"

Dear Sir:

I hope I am sending this inquiry to the right address. Please forward it elsewhere if I am sending it to the wrong address. I am conducting research into the question of a Shabbos bris for a child conceived through IVF or IUI, and I had a question related to the discussion in Nishmat Avraham v.3 (Chelek Even HaEzer) p.9. Dr. Avraham quotes R Shlomo Zalman, z"l, who deals with the question in light of Rabbeinu Chananel in Chagigah (16a). R Shlomo Zalman is trying to explain the basis for Rabbeinu Chananel's position, and he suggests that perhaps a woman who conceives in a bathtub doesn't fit the description 'tazria' because "eina mesaayat lehazra'at haba'al אינה מסייעת להזרעת הבעל". Does this mean that she does not participate in his releasing sperm (semen), or that she does not help him to inseminate her? In other words, is at that she is not with him at the beginning, when it leaves his body, or are we more concerned with her not bringing him to deliver the sperm into her? What is meant by the term 'hazra'at haba'al'?

Any and all assistance would be most appreciated.

Bivracha