The last several decades have seen women move into a huge variety of leadership positions - taking their places as strong forces in commerce and other fields. As women have furthered their education and pursued their careers, they've left off having a family in return. Then, once they hit their mid-to-late 30s and 40s, they realize that unless they have a baby soon, they won't have a baby at all. Many of these women end up relying on assisted reproduction therapies because they are unable to conceive.
It All Ages Together
Part of the reason conception is so difficult for older women is that their eggs have aged along with the rest of them. When it comes to reproduction, one of the strongest determinants for the probability of conception is the age of the female egg. So, what often happens is a woman at the age of 45 wants to have a baby and, for her age, the eggs she has in reserve in her ovaries are good. But, are they good enough to produce a normal, healthy, baby? The fact is that egg quality and quantity declines when a woman hits her mid-30s and it goes downhill from that point.
At present, there is no way to tell exactly how many eggs a woman has in reserve, nor how good they are. There are screening tests available, but they are less than perfect. These tests are often referred to as tests of ovarian reserve where they are testing the supply of eggs that remain in the ovaries. What are they testing for? With these tests, the quantity of the eggs can be determined, but there is little information about the quality of the eggs. Age is the best test that is available at present to determine the quality of the eggs.
Determining Quantity of Eggs
A 3-day FSH (follicle stimulating hormone) and an E2 (estradiol) test can sometimes give an indication that a woman is closer to menopause than not and has fewer eggs - and the quality of the eggs is reduced as well. There are several ways fertility specialists can determine the quantity of eggs in the ovarian reserve as part of fertility testing and procedures. One such way that fertility specialists evaluate ovarian reserve is with blood levels of the hormone AMH. Drugs (synthetic hormones) are used to challenge the ovaries and determine whether they have responded appropriately in order to tell which women have good egg reserves and which don't.
Older women (sorry, women over 35 are considered to be "older") have an increased risk for miscarriage because of the increase in chromosomal abnormalities in their eggs. There are two general types of chromosomal abnormalities:
Numerical abnormalities - there are an abnormal number of chromosomes
either a missing (monosomy) or an extra (trisomy) chromosome
Turner Syndrome, Down Syndrome, Edward's Syndrome
Structural Abnormalities - there is a problem with the structure of the chromosome
Translocations, duplication and deletion of part of the chromosome
As females age, it is aneuploid eggs and embryos that are responsible for the decline in fertility. They are also responsible for the low pregnancy success rates for women over the age of 40.
Increased Number of Faulty Eggs
Although the reason for the increase in the number of eggs with chromosomal abnormalities in older women is not fully known, research has provided a clarification of some of the issues involved.
One of the critical components of organizing the chromosome pairs in eggs so they divide properly is the meiotic spindle. If the spindle is abnormal, it can predispose to the development of chromosomally abnormal eggs. A study published in the medical journal "Human Reproduction" in October of 1996 investigated how the maternal age on the meiotic spindle was influenced un the assembly of human eggs. The findings showed that:
· chromosomally abnormal eggs are more common in older women
· 17% of eggs from women 20-25 years of age had an abnormal spindle appearance and at least one chromosome was displaced from proper alignment
· 79% of eggs from women 40-45 years of age had an abnormal spindle appearance and at least one chromosome displaced from proper alignment
When the chromosomes line up properly on the spindle in the egg, the division process is thought to proceed normally so the egg ends up with 23 pairs of chromosomes. When the arrangement is disordered on an abnormal spindle, the division process is uneven and results in unbalanced chromosomes in the egg. Older eggs are much more likely to have abnormally functioning spindles that cause an increased rate of chromosomal problems in the mature eggs.
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