Just found this on internet...
How often should we have sex?
Conceptions can occur up to seven days after intercourse, however, there is a significant decrease in the conception rate if intercourse occurs more than four days prior to ovulation. Optimal timing is every 36 hours around the time of ovulation, which is cycle day 14 or 15 for most women. In general, you should try to have intercourse every two to four days beginning on cycle day 10 extending through cycle day 18. In addition, it is beneficial to stay in bed for 30 minutes after intercourse. Semen coagulates immediately and dissolves 20 to 30 minutes thereafter releasing sperm. If the majority of this coagulum is expelled from the vagina prior to the sperm being released then there might not be enough sperm to allow fertilization. If your womb is retroflexed (flipped backwards), it may help for you to rest in a back up, knee to chest position after intercourse.
Could anyone please help me understand part in bold? Thanks!