What does Day 21 testing include?
Here's a quick hormone lesson:
When you ovulate, a follicle in your ovary releases an egg into the fallopian tubes, where it then travels down into the uterus. After the egg is released, the follicle left behind in your ovary releases a large amount of progesterone.
Therefore, when you undergo testing on Day 21, approximately 7 days after ovulation, your clinician should see a surge in progesterone. A high Day 21 progesterone level indicates ovulation and the release of an egg. A low Day 21 progesterone level suggests the cycle was anovulatory (no egg was produced). If no egg is produced, pregnancy cannot be achieved.
Additionally, estradiol (E2) is included in the Day 21 testing. This is a form of estrogen that is released as your egg follicles grow in the ovary. It peaks at ovulation.
Serial estradiol (E2) levels are often measured for monitoring superovulation in intrauterine insemination (IUI) and in vitro fertilization (IVF) treatment cycles, as it indicates follicular growth. Superovulation is the controlled stimulation of the ovaries as they are medically manipulated to produce more than one egg each month (normal ovulation produces only one egg each month).
An ultrasound exam is also used to measure your uterine lining to determine if it is thick enough for a fertilized egg to implant.