When Does the Luteal Phase Start?
The luteal phase occurs during the second half of the menstrual cycle, after ovulation has occurred.
It starts after ovulation, on day 15 of your cycle.
How Long is the Luteal Phase?
While the follicular phase, or first half, of the menstrual cycle can vary in length, in most women, the luteal phase is consistently about 14 days long.
Some women experience a shorter luteal phase, known as luteal phase deficiency (LPD), which is the result of decreased progesterone levels that result in inadequate development of the uterine lining. The significance of LPD is controversial. LPD is diagnosed based on a biopsy of the lining of the uterus. It has been found in women who experience infertility, as well as fertile women, which makes it challenging to interpret the findings of this testing.
What Happens During the Luteal Phase?
During the Luteal Phase, the follicle that burst and released the egg (during ovulation) develops into a small yellow structure, or cyst, called the corpus luteum.
The corpus luteum secretes progesterone and estrogen that cause the uterine lining, or endometrium, to thicken and be able to nourish a fertilized egg.
When sperm fertilizes an egg, the resulting embryo travels down the fallopian tube and implants in the uterus several days after ovulation.
The early embryo begins to make human chorionic gonadotropin (HCG), which maintains the corpus luteum and progesterone production. The corpus luteum will sustain the uterine lining and pregnancy until the placenta develops.
If the egg is not fertilized and an embryo does not implant, the corpus luteum deteriorates, and progesterone levels will fall. Without progesterone, the endometrium isn’t maintained and the uterus will start to shed its lining, resulting in menstruation.
Dr. Sydney Chang is a Fellow in Reproductive Endocrinology and Infertility at the Icahn School of Medicine at Mount Sinai/Reproductive Medicine Associates of New York. She earned her Bachelor of Arts in Human Biology at Stanford University, where she graduated with Honors and Distinction. She went on to complete her medical school education at Duke University School of Medicine. She completed her residency in Obstetrics, Gynecology, and Women’s Health at the Albert Einstein College of Medicine, where she served as an administrative chief resident.