What happens during the luteal phase?
The luteal phase includes several important events that prepare the body for pregnancy. Let’s take a closer look at what happens during this phase and what it means if this phase is longer or shorter than normal.
The luteal phase is the second half of your menstrual cycle. It starts after ovulation and ends with the first day of your period.
Once the follicle has released its egg, the egg travels down the fallopian tube, where it may meet sperm and be fertilized. The follicle itself then changes. The empty sac closes off, turns yellow, and transforms into a new structure called the corpus luteum.
The corpus luteum releases progesterone and some oestrogen. Progesterone thickens the lining of your uterus so that a fertilized egg can implant. Blood vessels grow inside the lining. These vessels will supply oxygen and nutrients to the developing embryo.
If you get pregnant, your body will also start to produce human gonadotropin (hCG). This hormone maintains the corpus luteum.
HCG enables the corpus luteum to keep producing progesterone until around the 10th week of your pregnancy. Then the placenta takes over progesterone production.
Progesterone levels rise throughout your pregnancy. Here’s a general guide:
- first trimester: 10 to 44 nanograms per millilitre (ng/mL) of progesterone
- second trimester: 19 to 82 ng/mL
- third trimester: 65 to 290 ng/mL
If you don’t get pregnant during this phase, the corpus luteum will shrink and die into a tiny piece of scar tissue. Your progesterone levels will drop. The uterine lining will shed during your period. Then the entire cycle will repeat.
Luteal phase length
A normal luteal phase can last anywhere from 11 to 17 days. In most women, the luteal phase lasts 12 to 14 days.
Your luteal phase is considered to be short if it lasts less than 10 days. In other words, you have a short luteal phase if you get your period 10 days or less after you ovulate. A short luteal phase doesn’t give the uterine lining a chance to grow and develop enough to support a growing baby. As a result, it can be harder to get pregnant or it might take you longer to conceive.
A long luteal phase may be due to a hormone imbalance like polycystic ovary syndrome (PCOS). Or, a long lapse since you ovulated could mean that you’re pregnant and you just haven’t realized it yet. The length of your luteal phase shouldn’t change as you age. But your progesterone levels during this phase may drop as you get closer to menopause.
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