3
Understanding Ovulation and
the Menstrual Cycle
The Menstrual Cycle
• The menstrual cycle is the process during which your body prepares
for pregnancy. Hormone changes during the cycle trigger the ovaries
to release an egg.
• The eggs are contained within fluid-filled cavities called follicles. Both
ovaries have many follicles, each containing an egg. During the first
part of the menstrual cycle, one of the follicles prepares to release an
egg. This follicle produces increasing amounts of estrogen, which
causes the lining of the uterus to thicken and the cervix to produce
‘fertile mucus.’ This “fertile mucus” is important (refer to page 4). A
high estrogen level triggers the surge of another hormone,
luteinizing hormone (LH). Ovulation normally occurs 24 to 36 hours
after the LH surge, when the follicle ruptures, releasing an egg.
• The egg can be fertilized for up to 24 hours after ovulation. If
fertilization does not occur, estrogen levels will gradually fall. The
lining of the womb is shed and the menstrual flow begins, marking
the start of the next cycle.
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