For a healthy couple, when the woman is younger than 30 years old, the chance for a healthy full-term pregnancy after well-timed sexual intercourse is no more than 15-20% each month. This is why, even for fertile couples, it could take up to 1 year of trying to get pregnant. Of course, about 30% of the couples achieve a pregnancy within 3 months of trying. These couples are considered the most fertile ones or the luckiest.
The basic steps to achieve a pregnancy are sperm production, oocyte production, the fertilization of the oocyte by the sperm, the formation of the embryo and the implantation of the embryo in the uterus.