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What is a Miscarriage?
Miscarriage is the loss of a pregnancy without obvious cause
before the 20th week. About 15% of known pregnancies end in
miscarriage, according to the American College of Obstetricians and
Gynecologists (ACOG). But the actual number is probably much higher
because many miscarriages occur so early in pregnancy that a woman
doesn't even know she's pregnant.
Most miscarriages occur before the 12th week of pregnancy. Signs
and symptoms include:
- Vaginal spotting or bleeding
- Pain or cramping in your abdomen or lower back
- Fluid or tissue passing from your vagina
Keep in mind that spotting or bleeding in early pregnancy is
fairly common. In most cases, women who experience light bleeding in
the first trimester go on to have successful pregnancies. Sometimes
even heavier bleeding doesn't result in miscarriage.
What Causes Miscarriage?
Most miscarriages occur because the fetus isn't developing
normally. Problems with the baby's genes or chromosomes are
typically the result of errors that occur by chance as the embryo
divides and grows — not problems inherited from the parents.
In a few cases, a mother's health condition — such as
uncontrolled diabetes, thyroid disease, infections, blood-clotting
problems, or problems with the uterus or cervix — may lead to
miscarriage.
Routine activities — such as exercising, having sex, working or
lifting heavy objects — can't provoke a miscarriage. Nausea and
vomiting in early pregnancy, even if it's severe, won't cause a
miscarriage. And a fall or other injury is unlikely to cause a
miscarriage, unless the injury is serious enough to threaten your
own life.
What Increases the Risk of Miscarriage?
Various circumstances increase the risk of miscarriage,
including:
- Age. Women older than age
35 have a higher risk of miscarriage than do younger women.
Paternal age also may play a role. In a 2006 study, women whose
partners were age 40 or older had a higher risk of miscarriage
than did women whose partners were younger than age 25.
- Previous miscarriages.
The risk of miscarriage is higher in women with a history of two
or more previous miscarriages. After one miscarriage, your risk of
miscarriage is the same as that of a woman who's never had a
miscarriage.
- Chronic conditions. Women
with certain chronic conditions, such as diabetes or thyroid
disease, have a higher risk of miscarriage.
- Uterine or cervical problems.
Certain uterine abnormalities or a weak or unusually short cervix
may increase the risk of miscarriage.
- Smoking, alcohol and illicit
drugs. Women who smoke or drink alcohol during pregnancy
have a greater risk of miscarriage than do nonsmokers and women
who avoid alcohol during pregnancy. Illicit drug use also
increases the risk of miscarriage.
- Caffeine. The evidence
linking caffeine consumption and miscarriage is inconclusive.
Because of the unknowns, your doctor may recommend limiting
caffeine intake to less than 200 milligrams a day.
- Invasive prenatal tests.
Some prenatal genetic tests, such as chorionic villus sampling and
amniocentesis, carry a slight risk of miscarriage.
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Maternal Excessive
Clotting: Thrombophilia
Known as Thrombophilia
is another Factor to Consider in Cases of Recurrent Pregnancy Loss
Recurrent pregnancy loss takes a
devastating emotional toll on our patients. Each miscarriage brings
with it a profound sense of loss and frustration. While hormonal,
uterine, immune system, and chromosomal abnormalities are widely
accepted as possible causes of repeat miscarriages, the latest
studies point to a new area of investigation - inherited blood
clotting factors.
When a patient has a tendency to form blood clots, the
condition is called thrombophilia. Thrombophilia can be a
life-threatening event if the clots restrict blood flow.
Thrombophilia can be an inherited disorder, but can also be caused
by external events such as surgery, obesity, pregnancy, use of oral
contraceptives, antiphospholipid syndrome, or long periods of
immobility.
Even though men and women can have
clotting disorders, these conditions pose added difficulties for
women because of their relationship to reproductive issues. Women
with these disorders can develop serious complications during
pregnancy leading to miscarriage. Pregnancy, oral contraceptives and
post-menopausal hormone replacement therapy are all triggering
events for DVT in women with thrombophilia (DVT or Deep Vein
Thrombosis is a blood clot that develops in a deep vein, usually in
the lower leg. Deep vein thrombosis can cause pain in the leg and
can potentially lead to complications).
In some individuals, excessive clotting in the
blood vessels never occurs until they have problems with placental
blood flow in a pregnancy. Under these circumstances, the blood
supply in the placenta (that is, the primary site of nutrition and
gas exchange between the mother and fetus) will be interrupted due
to clotting and this leads to a decrease in blood flow to the
developing fetus. As a result the fetus grows more slowly and is
smaller than expected (this is called intrauterine growth
restriction) and in severe cases, this may lead to late pregnancy
loss
Recent research indicates that patients who experience recurrent
miscarriage may have one or more of these markers for thrombophilia.
Recommended Tests for Patients with Recurrent Miscarriage
Ongoing research has uncovered new clues about possible reasons for
recurrent pregnancy loss. Because many of these conditions are
easily treated, physicians owe it to their patients to conduct
thorough evaluations. This is especially true considering these new
findings. We recommend that in addition to the usual infertility
panel (which would include testing for antiphospholipid antibodies,
lupus anticoagulant, and anticardiolipin antibodies), patients with
recurrent miscarriages should be tested for genetic markers of
thrombophilia, including:
Abnormal results on any of these tests may indicate an increased
risk of forming placental blood clots, deep vein thrombosis, and
potentially fatal pulmonary embolism during pregnancy. Because of
this, therapy should be strongly considered.
Because inherited thrombophilia has been shown to be a major
cause of recurrent miscarriage, patients with recurrent fetal loss
should be evaluated for clotting disorders, even in the absence of
clinical signs. This is especially true if the loss occurred after a
heartbeat was detected. When lab results show a clotting disorder,
consult your physician for appropriate treatments and follow-ups.
Can Miscarriage be Prevented?
In the vast majority of cases, there's nothing you can do to
prevent a miscarriage. Simply focus on taking good care of yourself
and your baby. Seek regular prenatal care, and avoid known risk
factors — such as smoking and drinking alcohol. If you have a
chronic condition, work with your health care team to keep it under
control.
Preliminary research suggests that treatment with aspirin or
another blood thinner to prevent blood clots may improve the chances
of a successful pregnancy for women with unexplained recurrent
miscarriages. If you've had three or more miscarriages without an
identifiable cause, ask your doctor if this might be an option for
you.
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