The fertility cycle is broken into two parts. The first half of the fertility cycle is when the follicle-stimulating hormone stimulates maturation of an egg. As the egg is maturing, estrogen levels rise causing the luteinizing hormone to increase. The luteinizing hormone forces the egg out of the follicle where maturation occurs.
After ovulation, the egg moves down the fallopian tube on the way to the uterus. Corpus luteum is left over in the fallopian tube. The corpus luteum signals a progesterone increase which leads to a thickening of uterine walls. These thick walls are perfect for the implantation of a fertilized egg. Corpus luteum is present in the fallopian tube for up to 14 days after ovulation. If it is not stimulated by human chorionic gonadotropin, progesterone and estrogen levels fall back to normal.
During the 14 days after ovulation, the body is prepared for egg fertilization and implantation.
When progesterone levels dive, the uterus gets the signal to start shedding that thicker layer. This shedding is when a normal menstrual period begins. Some women have periods that last just three days and others last seven days or more. Once all the uterine lining is shed, the menstrual cycle stops and the new fertility cycle begins.
Post ovulation is called the luteal phase and typically lasts between 12 and 14 days. Some women have a short luteal phase lasting less than 12 days. This makes the time frame for conception shorter.
Progesterone is key
If the corpus luteum dies off before the 12-day mark after ovulation and conception has already occurred, there may not be sufficient progesterone to sustain the pregnancy. In this case, a miscarriage could occur, but it may appear to be a heavier than normal menstrual cycle if a pregnancy test has not revealed pregnancy.
During the 14 days after ovulation, the body is prepared for egg fertilization and implantation. The uterine lining is thick and estrogen and progesterone levels are peaked. If fertilization occurs after ovulation, HCG levels will start to increase and the uterine lining will not receive the signal to shed. Most women are about one to two weeks pregnant when they miss their first menstrual cycle, though the pregnancy countdown is typically started from the last day of your last period.