Source : Varahahora and others.
1. The ovulation and menstrual cycles are caused by moon and mars. Moon is a watery planet and Mars is fiery by nature. Their combination makes pittha the rajas (ovum).
2. When the transit moon is placed in an upachaya rasi from the chandra rasi of the woman the uterus is unclean and insemination at that time will not yield pregnancy.
3. The moon placed in a non upachaya rasi should also be aspected by mars.
4. The man should have a transit moon placed in an upachaya rasi aspected by a benefic male planet (Guru).
5. The woman must be in her rutu period (ie:- 16 days form the first day of the menstrual cycle.)
6. Pregnancy occurs under the above circumstances if there is no hindrance due to past karma and the man's and woman's reproductive health is fine. The above are the conditions for normal conception.
7. If there is a problem in ovulation or menstruation due to prarabdha karma chandra and mars should be essentially propitiated.
8. If the problem does not have its roots in past karma it should be treated with medicine.
9. This makes 3 clear points. The ovum not getting fertilized during a cycle can be due to -
1. Unfavourable positions of moon and/or mars.
2. Past karma.
3. Health grounds.