About Fertility

What Is A Normal Menstrual Cycle?

What Is A Normal Menstrual Cycle?

The purpose of the menstrual cycle is to prepare the uterus for pregnancy. Understanding how your period affects your chances of pregnancy is an important part of understanding your fertility. Many patients ask what is a normal menstrual cycle? It depends on an orderly progression of hormonal signals and is simplistically divided into the following phases:

  1. Proliferative/ Follicular Phase
  2. Ovulatory Phase
  3. Secretory/Luteal Phase
  4. Menstrual Phase

When is Cycle Day 1?

Cycle Day #1 is defined as the start of vaginal bleeding generally defined as flow not spotting. This is also called by some the Menstrual Phase and usually lasts 2 to 6 days with the median being 4 days of duration. Bleeding is usually the heaviest on the first two days of your cycle. Once the bleeding ceases, the endometrium (uterine lining) begins the process of preparing for the possibility of pregnancy.

How Do I Figure Out My Cycle Length?

Cycle length is defined as Cycle Day #1 to Cycle Day #1 of your next period. In 90% of women, the cycle length is between 24 and 35 days with 15% having an idealized 28 day cycle.

The Proliferative / Follicular Phase

The Proliferative/Follicular Phase of the menstrual cycle is variable in length generally between 7 and 21 days. It includes the maturation of ovarian follicles to prepare one of them for release during ovulation. The follicular phase is also known as the “proliferative phase” because rising levels of estradiol (estrogen) levels cause the endometrial lining of the uterus to proliferate and thicken.

The Ovulatory Phase

The ovulatory phase occurs in the middle of your cycle, typically around day 14, and is followed by the Secretory/Luteal Phase generally lasting 12 or more days and is more constant than the Proliferative/Follicular Phase.

The Secretory / Luteal Phase

A Secretory/Luteal Phase occurs from day 14 to day 28 of the cycle. Progesterone stimulated by LH (luteinizing hormone) prepares the corpus luteum and the endometrium for possible implantation. A Secretory \ Luteal Phase that is less than 12 days is called Luteal Phase Insufficiency.

It was historically thought to be associated with infertility, however, a recent study by Crawford et al published online (FertilSterile Pub 2017Jan 5) found that a short luteal phase was not associated with infertility after 12 months of attempting pregnancy. After adjustment for age, women with a short luteal phase were less likely to become pregnant short-term but not long-term. A short luteal phase (<11 days including day of ovulation) was found in 18% of 1,635 cycles from 284 women aged 30 to 44 years. Significantly more women with a short luteal phase were smokers.

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We encourage patients to have a healthy lifestyle to have the best chances of conceiving. If you have more questions on what is a normal menstrual cycle or are having difficulty conceiving, please contact us to set up your consultation.

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