OVARIAN RESERVE (FSH) TESTING
Normal ovarian aging begins when the female fetus is inside
her mother's uterus. The maximal number of eggs, approximately
six to seven million, are found inside the ovaries of a
female fetus at approximately five months of pregnancy.
Through the natural process of reproductive aging, only
one to two million eggs are left at the time a baby girl
is delivered. Several hundred thousand eggs remain when
a young woman enters puberty. Every month thereafter (even
during pregnancy and while taking birth control pills),
several hundred to one thousand eggs awaken from their hibernation
and are eligible to be ovulated Typically, only one egg
is released monthly. The other eggs are resorbed. The result
is that women are losing eggs at a fairly constant rate
throughout much of their reproductive life.
In a classic study published in the New England Journal
in 1982, French researchers demonstrated that the likelihood
of establishing a pregnancy did not decline until a woman
reached age twenty-five. There was a very mild drop in monthly
fertility from the age of twenty-five to thirty, which was
slightly accelerated between the ages of thirty and thirty-five.
Between the ages of thirty-five and forty, fertility rates
fell significantly. This decline was even more highly accelerated
after the age of forty. Worldwide experience with in
vitro fertilization has shown a similar decline in fertility
beginning in the mid thirties, with a more severe loss of
fertility after the age of forty. This reduced in fertility
appears entirely due to diminishing egg quality and quantity.
It has been known for approximately ten years that measuring
follicle
stimulating hormone (FSH)
levels on the second, third, or fourth day of a woman's
menstrual period is highly predictive of future fertility.
The FSH assay at Northern Fertility and Reproductive Associates
has been correlated with the largest data base known. An
FSH level > 14 IU/L is associated with a 5% chance of
achieving a pregnancy over several years time. Women with
elevated FSH levels have less than a 1% take home baby rate
from a cycle of in vitro fertilization. While it is true
that elevated FSH levels mostly affect women in their late
thirties and early forties, a young woman with an elevated
FSH level has a very poor prognosis for establishing a pregnancy
without the use of donor
eggs. Our donor egg program has a 70% per cycle pregnancy
rate. The role of ovulation
induction using medications like clomiphene
citrate and injectable FSH has not been well-studied in
women with diminished ovarian
reserve. We have had successful pregnancies using ovulation
induction medications in some women with diminished ovarian
reserve.
There are some women with a normal day three FSH level who
still have diminished ovarian reserve. Such women, typically
in their late thirties and early forties, or with prior
ovarian surgery, can be identified with the use of a clomiphene
citrate challenge test (CCCT). Clomiphene citrate (100
mg) is taken daily, starting on cycle day five for a total
of five days. On cycle day ten, an FSH level is again drawn.
FSH levels > 14 IU/L on day ten are also indicative of
diminished reserve. Though few studies exist, it appears
that a single elevated FSH level represents severely diminished
ovarian reserve and a poor prognosis for pregnancy, even
if FSH testing in subsequent months is normal. The use of
donor eggs is currently the only effective form of therapy
for women with elevated FSH testing.
