Ovarian aging versus chronological aging in the menopause transition
Posted by: Jeannie Merrick W.H.C.N.P, Women’s Health care Nurse Practitioner in Primary Care
Feb 21, 2012
Most women know that menopause is marked by their last menstrual period and signifies the end of their fertility. What about fertility from the time the menstrual cycles begin to change to the time of menopause? This is called the menopause transition and fertility during this time is significantly reduced.
The menopause transition, sometimes called the peri-menopause, starts when menstrual cycles begin to change and ends with the final menstrual period (recognized only after 12 consecutive months of no menses). Ninety percent of women experience four to eight years of menstrual changes before their natural menopause.
Age can't predict menopause onset
In the United States, natural menopause occurs at an average age of 51.4 years but is considered normal any time between the ages of 40 to 60. Because women vary widely in the timing of their menopause transition, age alone is an inaccurate predictor of a woman's reproductive age.
If a woman is destined to have her last menstrual period at age 42, she will likely experience difficulty trying to conceive by the age of 34 to 37. The decrease in fertility depends on the quality of her eggs and to some extent, the declining number of eggs.
How egg loss happens
During a woman's fetal development she will have 1 to 2 million oocytes (eggs) in her ovaries. Follicular loss begins in utero and by the time she is born, she will have approximately 600,000. While that is still a huge number, many women wonder how we lose so many eggs so quickly.
Most follicular loss occurs through a process called apoptosis or atresia and not by ovulation. As a woman goes through her monthly menstrual cycle, she will recruit or "awaken" a number of follicles all vying to become the follicle of the month. Most of these awakened follicles will die off, leaving only one that continues to grow and ovulate. At age 17, a woman may awaken as many as 20 to 40 eggs each month. By age 30, that number can drop to 10 or 15 and by age 40 she will likely recruit only two to four follicles.
This oocyte die-off is continuous and occurs even if a woman is on birth control medication. For most women, the process begins to accelerate around the age of 37 until menopause.
For more information
If a woman has not completed her family and is interested in knowing her ovarian "reproductive age" there is testing available. Contact me, Jeannie Merrick, R.N., W.H.C.N.P., at Oak Street Medical for an appointment.
