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Overview
1 in 10 women and birthing people don't know their cycle length.1
Understanding your cycles and what happens throughout each phase in your cycle can help improve the chances of conception and identify when additional support may be needed.2
Despite most people focusing on ovulation for conception, nearly half of women and birthing people of child-bearing age (18 years and above) do not know what ovulation is, and over two thirds are not aware of the timing in their cycle for ovulation.3 However, there is a phase that follows ovulation that has a critical role for implantation and establishing early pregnancy, this is known as the luteal phase.4
The menstrual cycle
The menstrual cycle consists of two main phases:5
- The follicular phase
- And
- The luteal phase
Ovulation is a transitional event that occurs between these phases.5 The two phases reflect the body’s response to changing levels of reproductive hormones, primarily oestrogen and progesterone. It is this rise and fall in reproductive hormones which prepares the body for conception, establish and maintain a pregnancy, or where conception has not occurred, shed the uterine lining to prepare for another cycle.5
The Follicular phase
The start of each menstrual cycle, and the start of the follicular phase, is counted from the first day of menstruation (period). During this phase, a hormone known as the follicle-stimulating hormone (FSH) is released and prepares the growth of several ovarian follicles for egg release (ovulation).5
The length of the follicular phase varies between individuals. It is often around 14 days; however, it can be shorter or longer, typically ranging between 10 and 18 days long. These variations in follicular phase duration cause the differences found in the overall length of each menstrual cycle.5,6
Ovulation
Once FSH has prepared follicles in the ovary, levels of oestrogen increase to support the selection of a dominant follicle (the one that will release an egg).6 Oestrogen also triggers the production of the luteinizing hormone (LH).2,6 This sudden spike in LH is what releases the egg from the ovary (ovulation), and kick starts the luteal phase.6
Luteal phase
The luteal phase is the part of the cycle that follows ovulation. It typically lasts 12–14 days, but can vary between 11–17 days.4
After releasing the egg, the follicle transforms into the corpus luteum, a temporary hormone‑producing gland formed under the influence of LH. The corpus luteum produces progesterone, which:
- prepares the uterine lining for implantation
- maintains the lining in early pregnancy
- suppresses new follicle development
If pregnancy does not occur, the corpus luteum breaks down, progesterone levels fall, and menstruation begins. If implantation is successful, and a pregnancy is established, human chorionic gonadotropin (hCG), the hormone responsible for giving those two lines on a pregnancy test, is produced which helps to support the CL to continue producing progesterone to sustain the pregnancy.4
Why support the luteal phase?
When you understand what happens during the luteal phase of the menstrual cycle, you realise that progesterone is an essential detail in the conception process. If the luteal phase is too short or not working properly, the body may not make enough progesterone to maintain the uterine lining. This can make it difficult for a pregnancy to continue, even if an egg has been fertilised. This often leads to fertility difficulties and may result in miscarriage.2,4