Though a woman retains fertility for as long as
she ovulates and has menstrual cycles (even if
irregular), her fertility diminishes as she
approaches menopause. Menstrual cycles and
ovulation often become irregular in timing, and
anovulatory cycles (menstrual cycles without ovu-
lation) become more common. Other factors that
influence fertility in women include
- oral contraceptives (birth control pills), which
override the body’s hormonal regulation of the
menstrual cycle, or estrogen suppression ther-
apy, such as to treat severe uterine fibroids or
ENDOMETRIOSIS
•TURNER’S SYNDROME
- PREMATURE OVARIAN FAILURE(POF), in which the
OVARIES stop functioning before natural
menopause - TUBAL LIGATION(surgery to “tie” or cut the FAL-
LOPIAN TUBESas a permanent form of CONTRACEP-
TION) - HYSTERECTOMY(surgery to remove the uterus)
- chronic PELVIC INFLAMMATORY DISEASE(PID), which
may SCARand block the fallopian tubes - CHEMOTHERAPYor RADIATION THERAPYto treat can-
cer anywhere in the body
Male Fertility and Conception
Male fertility relies on the motility (movement
and thrust), morphology (physiologic form), and
volume of sperm present in the ejaculate (SEMEN
that leaves the man’s PENISwith EJACULATION). Lab-
oratory examination of a sperm sample measures
these and other factors; there are no home tests
for sperm viability. Sperm can live about 72 hours
in the woman’s reproductive tract, though the
environment of the VAGINAis particularly hostile,
and about half of the 500 million or so sperm typi-
cally present in a fertile man’s ejaculate die during
their passage through the it. However, dead and
dying sperm are important to fertility because they
provide protection and support for living, motile
sperm. Dead sperm help form a protective barrier
around surviving sperm. The movement of dying
sperm helps propel onward the cluster of sperm
that remain viable.
One healthy, functioning testicle is adequate to
produce enough sperm for fertility. Though a man
remains fertile all his life the quality of his sperm
(motility, morphology, and other characteristics)
tends to decline in his later years (age 70 and
older). This may become an issue in regard to fer-
tility if the woman’s fertility is marginal. Other
factors that influence male fertility include- inflammatory damage to the TESTICLESdue to
bacterial or viral INFECTION - RETROGRADE EJACULATION(semen enters the BLAD-
DERinstead of leaving the penis during ejacula-
tion) - PROSTATECTOMY(surgery to remove the PROSTATE
GLAND) - VASECTOMY(surgery to clip or cut the VAS DEFER-
ENSas a means of permanent contraception) or
ORCHIECTOMY(surgery to remove a testicle) - CRYPTORCHIDISM(undescended testicle), particu-
larly bilateral or delayed diagnosis - ERECTILE DYSFUNCTION
- chemotherapy or radiation therapy for cancer
anywhere in the body
- chemotherapy or radiation therapy for cancer
Body temperature also affects male fertility.
Normally the SCROTUM(saclike structure that con-
tains the testicles) rises and lowers to maintain
ideal temperature for spermatogenesis (production
of new sperm). FEVER, sitting in a hot tub, and
wearing clothing that holds the scrotum tight
against the body are factors that can raise the tem-
perature in the testicles to one at which sperm
cannot survive. Though these often are temporary
factors, they may be permanent.
See also AGING, REPRODUCTIVE AND SEXUAL
CHANGES THAT OCCUR WITH; ASSISTED REPRODUCTIVE
TECHNOLOGY(ART); STILLBIRTH.fetus The stage of prebirth development from
nine weeks of gestation to birth. The organ sys-
tems and major structures take form during the
EMBRYOstage, which encompasses the second to
the eighth weeks of gestation. During the fetal
stage, which is 32 weeks in a full-term PREGNANCY,
the systems, organs, and structures grow and
develop further sophistication in preparation for
independent life. The fetus reaches viability (possi-
bility of surviving on its own) at around 24 weeks
of gestation.fetus 283