The follicular phase explained

The follicular phase explained

The follicular phase starts on the first day of menstruation and continues until ovulation. During this time the ovaries and uterus prepare for a possible pregnancy. Follicles grow in the ovaries and the uterine lining builds up again.

What happens during this phase

At the start of the cycle FSH, follicle stimulating hormone, stimulates several follicles in the ovaries to grow. Each follicle contains an immature egg. One follicle becomes dominant and continues to mature. At the same time the uterine lining rebuilds under the influence of estrogen.

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The role of estrogen in this phase

As the follicles grow, they produce estrogen. Estrogen levels gradually rise duringthis phase. Estrogen causes the uterine lining to thicken and prepares it forpossible implantation.

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Transition to ovulation

When the dominant follicle has matured and estrogen levels are high enough, a rise in LH occurs. This rise leads to ovulation and marks the end of the follicular phase.

Why this phase is important

The follicular phase is the part of the menstrual cycle between menstruation and ovulation. During this time, the egg matures and the uterus is prepared.

Sources and references

Cleveland Clinic, Follicular phase https://my.clevelandclinic.org/health/body/23953-follicular-phase

NHS, Fertility in the menstrual cycle https://www.nhs.uk/conditions/periods/fertility-in-the-menstrual-cycle/