CONTRACEPTION, BARRIER METHODS OF
C
prevent
ovulation
in the woman; others
stop
sperm
from meeting an
ovum
in the
fallopian tube
(preventing
fertilization
) ,
or
prevent
a
fertilized
ovum
from
implanting in the
uterus
.
Some contraceptive methods involve
changes in sexual activity; such methods
include total or periodic abstinence from
intercourse
(see
contraception,
natural
methods of
)
and
coitus interruptus
,
in
which
sexual
intercourse
is
stopped
before ejaculation occurs. Other meth-
ods,
known as barrier methods
(see
contraception, barrier methods of
) ,
involve
the use of condoms to prevent sperm
from coming into contact with eggs.
Hormonal methods, including the use
of
oral contraceptives
,
implants,
and
injections (see
contraceptives, injectable
) ,
prevent conception by altering the hor-
mone balance in a woman’s body Further
forms of contraception include the use of
intrauterine devices (see
lUDs
) ;
postcoital
methods (see
contraception, emergency
) ;
or
sterilization of the male (see
vasectomy
)
or female (see
sterilization, female
) .
contraception, barrier methods of
The use of a device and/or a chemical
that w ill physically stop
sperm
from
reaching an
ovum
,
thus preventing
fertil-
ization
and pregnancy. Barrier methods
and
spermicides
(preparations that kill
sperm), when used together correctly,
can be highly effective in preventing
conception. Barrier methods of contra-
ception also help to prevent the sexual
transmission of diseases such as
HIV
,
genital herpes (see
herpes, genital
), and
viral hepatitis (see
hepatitis, viral
).
The male
condom
,
a latex sheath that
covers the penis, is one of the most
widely used barrier contraceptives. The
female condom
(see
condom, female
) ,
w hich lines the vagina, is sim ilar to the
male condom but is larger.
Other barrier methods that are used
by women include the diaphragm and
the cap. The diaphragm (see
diaphragm,
contraceptive
) is a hemispherical dome
of thin rubber with a metal spring in
the rim to hold it in place against the
vaginal wall, blocking the entrance to
the
cervix
.
It is used with a spermicide.
A cervical cap (see
cap, cervical
)
is an
alternative to the diaphragm.
Spermicides, in the form of aerosol
foams, creams, gels, and pessaries, are
placed in the vagina as close as possible
to
the
cervix
shortly
before
sexual
intercourse. Although some condoms
are precoated with spermicide, not all
types of spermicide should be used
with rubber barrier devices. (See also
the illustrated box on previous page.)
contraception, emergency
Measures to avoid
pregnancy
following
unprotected
sexual intercourse
.
There are
two main methods: hormonal and phys-
ical. In the first,
oral contraceptives
(the
“morning after” pill) should be taken in
a high dose as soon as possible after
unprotected sexual intercourse: prefer-
ably w ithin
12
hours, but no later than
72 hours afterwards. The pills contain a
high dose of the hormone
progesterone
.
In the physical method, an
IUD
is inserted
by a doctor within five days of unpro-
tected sex. Both methods are thought to
work by preventing a fertilized egg
from implanting in the uterus. (See also
the illustrated box on previous page.)
contraception, hormonal
methods of
The use by women of synthetic
pro-
gestogen drugs
,
often combined with
synthetic
oestrogens
,
to prevent concep-
tion.
The
combined
pill
(see
oral
contraceptives
) ,
the best-known form of
hormonal contraception, contains both
an oestrogen and a progestogen; it acts
by suppressing
ovulation
(the release of
an egg from an ovary). Progestogen
drugs make cervical mucus thick and
impenetrable to sperm. They also cause
thinning of the
endometrium
(lining of
the uterus), w hich reduces the chance
of a fertilized egg implanting success-
fully. Progestogens can be given as pills,
as
contraceptive implants
under the skin,
or by injection (see
contraceptives, inject-
able
), or they can be released into the
uterus by some
lUDs
.
(See also the illus-
trated box on previous page.)
contraception, natural methods of
Methods of avoiding conception that
do not involve the use of any contra-
ceptive
hormones
or
devices. These
methods are based on attempts to p in-
point a woman’s fertile period around
the time of
ovulation
,
so that sexual
intercourse
can be avoided at this time.
The
calendar method
is based on the
assumption that ovulation takes place
around 14 days before menstruation.
Due to its high failure rate, it has been
largely superseded by other methods.
The
temperature method
is based on
the normal rise of a woman’s body
temperature in the second half of the
menstrual
cycle,
after
ovulation
has
occurred. The woman takes her temp-
erature each day using an ovulation
thermometer. Sex is considered to be
safe only after there has been a rise in
temperature lasting at least three days.
The
cervical mucus method
involves
attempting to pinpoint the fertile per-
iod by charting the appearance and
amount of cervical mucus during the
menstrual
cycle.
Certain
recognized
changes in the mucus occur before and
often at ovulation. The
symptothermal
method
is a combination of the temper-
ature and mucus methods. (See also the
illustrated box on previous page.)
contraception, postcoital
See
contraception, emergency
.
contraception, withdrawal
method of
See
coitus interruptus.
contraceptive
Any agent that reduces the likelihood of
conception
.
(See also
contraception
. )
contraceptive implant
A hormonal method of
contraception
in
w hich a long-acting
progestogen drug
is
inserted
under
the
skin
inside
the
upper arm. An implant consists of a
small, flexible rod that steadily releases
the drug into the bloodstream. It func-
tions continually for several years.
contraceptives, injectable
A hormonal method of
contraception
in
which long-acting
progestogen drugs
are
injected
every
two
to
three
months.
Injectable contraceptives are very effec-
tive,
but
they
may
cause
menstrual
disturbances, weight gain, headaches, and
nausea, especially in the first few months.
contractions, uterine
Rhythmic, squeezing muscular spasms
that occur in the walls of the
uterus
before and during
childbirth
in order to
expel the baby from the uterus. Regular
contractions indicate the start of
labour
and increase in strength and frequency
throughout the first stage.
(See also
Braxton Hicks’ contractions.
)
contracture
A deformity that is caused by shrinkage
of tissue in an area of skin, muscle, or
a tendon and that may restrict the
movement of a joint. Skin contractures
commonly occur as a result of scarring
following
extensive
burns
or
other
194
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