Since there isn’t a baby yet by week 1, your body is getting ready for pregnancy by preparing an egg for fertilization. The egg is the largest single cell in the female body, and it starts maturing at the beginning of each cycle so that it can be released during ovulation. This process is called the ovarian cycle.
You are in the follicular phase. The beginning of this phase coincides with the start of your period. At first, a hormone called FSH, or follicle-stimulating hormone, causes many immature follicles to begin preparing for ovulation.
But by day 5-7 of your cycle, one follicle, containing one egg, has become dominant. The dominant follicle usually has a stronger blood supply and produces more estrogen.
During the follicular phase, the egg within this dominant follicle matures and then waits for ovulation. So, it’s a race of eggs. The winner will burst out of the follicle (a tiny cystic structure where the egg grows)to travel through one of your tubes –but not quite yet.
There isn’t an exact answer to why one follicle becomes dominant and not others, but it is established that once the dominant, the follicle will release estrogen then suppress the other follicles. These other follicles then wither away and disappear into the ovary. Estrogen will also stimulate the thickening of the uterine lining.
Having a healthy pregnancy largely depends on the quality of the egg and sperm cells, which typically contain 23 chromosomes each. These chromosomes contain all of your and your partner’s genetic information, which is combined during fertilization.