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Currently, in the United States, about 20% of
couples struggle with infertility at any given time. Infertility has
increased as a problem over the last 30 years. Some studies pin the
blame for this increase on social phenomena, including the tendency
for marriage to occur at a later age, which means that couples are
trying to start families at a later age. It is well known that
fertility in women decreases with increasing age, as illustrated by
the following statistics:
- Infertility in married women ages 16-20=4.5%
- Infertility in married women ages 35-40=31.8%
- Infertility in married women over the age of 40=70%.
Nowadays, individuals often have multiple sexual
partners before they marry and try to have children. This increase
in numbers of sexual partners has led to an increase in sexually
transmitted diseases. Scarring from these infections, especially
from pelvic inflammatory disease (a serious infection of the female
reproductive organs, most commonly caused by gonorrhea) seems to be
in part responsible for the increase in infertility noted.
Furthermore, use of some forms of the contraceptive called the
intrauterine device (IUD) contributed to an increased rate of pelvic
inflammatory disease, with subsequent scarring. However, newer IUDs
do not lead to this increased rate of infection.
To understand issues of infertility, it is first
necessary to understand the basics of human reproduction.
Fertilization occurs when a sperm from the male merges with an egg (ovum)
from the female, creating a zygote that contains genetic material (DNA)
from both the father and the mother. If pregnancy is then
established, the zygote will develop into an embryo, then a fetus,
and ultimately a baby will be born.
The male contribution to fertilization and the
establishment of pregnancy is the sperm. Sperm are small cells which
carry the father's genetic material. This genetic material is
contained within the oval head of the sperm. The sperm are mixed
into a fluid called semen, which is discharged from the penis during
sexual intercourse. The whip-like tail of the sperm allows the sperm
to swim up the female reproductive tract, in search of the egg it
will try to fertilize.
The female makes many contributions to
fertilization and the establishment of pregnancy. The ovum is the
cell that carries the mother's genetic material. These ova develop
within the ovaries. Once a month, a single mature ovum is produced,
and leaves the ovary in a process called ovulation. This ovum enters
a tube leading to the uterus (the fallopian tube). The ovum needs to
meet up with the sperm in the fallopian tube if fertilization is to
occur.
When fertilization occurs, the resulting cell (which
now contains genetic material from both the mother and the father)
is called the zygote. This single cell will divide into multiple
other cells within the fallopian tube, and the resulting cluster of
cells (called a blastocyst) will then move into the womb (uterus).
The uterine lining (endometrium) has been preparing itself to
receive a pregnancy by growing thicker. If the blastocyst
successfully reaches the inside of the uterus and attaches itself to
the wall of the uterus, then implantation and pregnancy have been
achieved. |