A
spontaneous abortion is the loss of a fetus during pregnancy
due to natural causes. The term "miscarriage"
is the spontaneous termination of a pregnancy before fetal
development has reached 20 weeks. Pregnancy losses after
the 20th week are categorized as preterm deliveries.
The
term "spontaneous abortion" refers to naturally
occurring events, not elective or therapeutic abortion procedures.
Other
terms include:
-missed
abortion (a pregnancy demise where nothing is expelled)
-incomplete abortion (not all of the products of conception
are expelled)
-complete abortion (all of the products of conception are
expelled)
-threatened abortion (symptoms indicate a miscarriage is
possible)
-inevitable abortion (the symptoms cannot be stopped, and
a miscarriage will happen)
infected abortion
-Causes, incidence, and risk factors
The
cause of most spontaneous abortions is fetal death due to
fetal genetic abnormalities, usually unrelated to the mother.
Other possible causes for spontaneous abortion include infection,
physical problems the mother may have, hormonal factors,
immune responses, and serious systemic diseases of the mother
(such as diabetes or thyroid problems).
It
is estimated that up to 50% of all fertilized eggs die and
are lost (aborted) spontaneously, usually before the woman
knows she is pregnant. Among known pregnancies, the rate
of spontaneous abortion is approximately 10% and usually
occurs between the 7th and 12th weeks of pregnancy.
The
risk for spontaneous abortion is higher in women over age
35, in women with systemic diseases such as diabetes or
thyroid problems, and women with a history of three or more
prior spontaneous abortions.
Possible
symptoms include:
-Low-back
pain or abdominal pain that is dull, sharp, or cramping
-Vaginal bleeding, with or without abdominal cramps
-Tissue or clot-like material that passes from the vagina
-However, about 20% of pregnant women have some vaginal
bleeding during the first trimester. Approximately half
of these women have a spontaneous abortion.
During
a pelvic exam, your healthcare provider may see moderate
thinning of your cervix (effacement), increased cervical
dilation, and evidence of ruptured membranes.
The
following tests may be performed:
-HCG
(qualitative urine) or HCG (qualitative blood serum) to
confirm pregnancy
-HCG (quantitative) values drawn at intervals of days to
weeks
-CBC to determine the degree of blood loss
-WBC and differential to rule out infection
An abortion, especially if incomplete or missed, may also
alter the results of the following tests:
-Transvaginal
ultrasound
-Pregnancy ultrasound
-Estriol - urine
-Estriol - serum
-Serum progesterone
-Fibrin degradation products
The treatment for a threatened abortion varies from restricting
some forms of exercise to complete bed rest. Abstaining
from intercourse is usually recommended until the warning
signs have disappeared.
If
a spontaneous abortion occurs, the signs of pregnancy decrease,
the uterus begins shrinking to its original size, and a
brownish or reddish vaginal discharge is often experienced.
The tissue passed from the vagina should be examined to
determine the source (fetal vs. hydatidiform mole). It is
also important to determine whether any fetal tissue remains
in the uterus. This is called an incomplete spontaneous
abortion.
If
remaining tissue is not naturally aborted in a reasonable
amount of time (about 4 weeks), surgery (D and C or D and
E) or medication will be required to complete the abortion.
Medications include mifepristone, methotrexate, misoprostol,
or a combination of these medications. Most women who use
these medications do so because of a desire to avoid anesthesia
and surgery if at all possible.
Side
effects of the medication may include nausea, vomiting,
diarrhea, warmth or chills, headache, more visits to the
doctor’s office, prolonged vaginal bleeding, and being more
aware of cramping than with surgical abortion. With medication,
passage of the products of conception most likely will occur
at home, but some women may still require surgical evacuation
(D and E) to complete the abortion. The success rate has
been shown to be around 95%.
Once
the tissue is removed, the woman usually resumes her normal
menstrual cycle within a few weeks. Any further vaginal
bleeding should be carefully monitored. It is often possible
to become pregnant immediately, but the woman should usually
wait for 1 or 2 normal menstrual cycles before trying to
become pregnant again.
Complications
in the mother are rare. However, possible complications
include:
Retained
fetal tissue (an incomplete abortion) may cause an infection
and must be removed surgically.
An infection also may occur after a complete abortion. The
death of a second- or third-trimester pregnancy is addressed
differently than a first-trimester loss. If the fetus remains
in the uterus for too long, an abnormal activation of blood
clotting systems can develop. This can threaten the mother's
health.
Call
your health care provider if vaginal bleeding with or without
cramping occurs during pregnancy.
Call
your health care provider if you are pregnant and notice
tissue or clot-like material passed vaginally (any such
material should be collected and brought in for examination).
Many
spontaneous abortions that are caused by systemic diseases
can be prevented by detecting and treating the disease before
becoming pregnant.
Spontaneous
abortions are less likely with early, comprehensive prenatal
care and by avoiding environmental hazards (such as x-rays
and infectious diseases).
When
a mother's body is having difficulty sustaining a pregnancy,
signs (such as slight vaginal bleeding) may occur. This
is a threatened abortion, which means there is a possibility
of abortion, but it is not inevitable. A pregnant woman
who develops any signs or symptoms of threatened miscarriage
should contact her prenatal provider immediately.
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