How many times during ovulation can increase the chances of conception? What are the conditions for female conception?

How often should intercourse take place during ovulation for high pregnancy rates? We know that once an egg is released, it can only survive for 12 to 24 hours and sperm can only live for 1 to 3 days. Therefore, in order to successfully conceive, having intercourse every 2 days within a week before ovulation increases the chances of pregnancy.

What conditions must be met for a woman to conceive?
1. A mature and normal sperm and egg;
2. Unobstructed reproductive tracts;
3. Appropriate environment for conception with a normal endometrium inside the uterus;
4. Timing of fertilization of the egg must be appropriate.

Reasons why women cannot get pregnant during ovulation?
1. It might be due to cervical diseases which are important causes of infertility accounting for 10-20% of infertility cases. Chronic cervicitis or low levels of estrogen could make cervical mucus sticky or contain excessive amounts of white blood cells, thus hindering the activity and passage of sperms and affecting pregnancy rate. Besides, cervical polyps or muscle tumors could obstruct cervical canal which makes it difficult for sperms to pass through narrow cervix outlets also causing infertility.
2. It might be caused by local ovarian factors such as congenital absence of ovary or immature ovary, early ovarian failure, polycystic ovaries, some ovarian tumors such as granulosa-theca cell tumor and ovarian stromal cell tumor that could affect hormone secretion and ovulation respectively.
3. It might be due to systemic disease in women or lack of certain nutritional factors in diet which could affect ovarian function resulting in infertility.
4. It could be caused by mental factors such as mental tension and anxiety that inhibit ovulation thus leading to inability to conceive as well.
5abnormalities in genital organs: Congenital abnormalities or postnatal lesions can block the reproductive channels from external vulva to fallopian tube thus hindering meeting between sperms and eggs resulting in infertility .
6Antibodies against male sperms: There may exist antibodies against male sperms either in female reproduction tract or serum which aggregate male sperms causing death or losing vitality thereby resulting in infertility or sterility .
7Low quality sperm from men: Low quality sperm from men such as no sperm , weak sperm etc., may influence conception rate too .