RECURRENT ABORTION
Recurrent abortion is the spontaneous loss of two consecutive, or three total, first-trimester pregnancies regardless of the outcome of other pregnancies. (Some definitions restrict this definition to three consecutive losses.) This is estimated to affect between 0.4% and 0.8% of reproductive-age women. Problems with the chromosomal makeup of the embryo, the hormonal environment of the pregnancy, or physical attributes of the uterus or endometrium may play a role in these losses. Risk factors for recurrent pregnancy loss are the same as those associated with single spontaneous abor- tion, including increasing maternal and paternal age, certain medical illnesses like uncontrolled diabetes mellitus and thrombophilias, and autoimmune disorders. In 40% of cases, no risk factor or cause will be identified. In general, about 70% of these patients will have a subsequent normal pregnancy without intervention.
When pregnancy losses occur early in gestation, there is a greater
likelihood that a chromosomal abnormality is the cause, whereas for later abortions,
a maternal cause such as a uterine anomaly is more likely. Although most
chromosomal abnormalities result from disorders of meiosis in gamete formation or
in mitosis after fertilization, 5% of couples that experience recur- rent abortion
have a detectable parental chromosomal balanced abnormality. For this reason, karyotyping
of both parents is recommended when recurrent early abortions have occurred. When
available, karyotyping of the abortus may be helpful but requires fresh tissue,
specialized transport media, and appropriate laboratory capabilities. Those with
parental chromosomal anomalies may be offered donor oocytes or artificial insemination with donor sperm to overcome the problem.
Two-thirds of recurrent abortions occur after 12 weeks’ gestation, which suggests
that maternal or environmental factors play a larger role in this process
than do genetic conditions. Surgically correctable uterine abnormalities, an incompetent
cervix, or intrauterine septa or synechiae are the most common uterine abnormalities
associated with early pregnancy loss. Indeed, uterine anomalies are found in 15%
to 25% of women with recurrent abortion. When uterine anomalies are suspected, hysteroscopy
is preferred for both diagnosis and therapy. Uterine anomalies or submucous fibroids
may be treated in this way, although care must be taken to recognize the possibility
of continued failure for other reasons and the possible impact on future delivery
options made by such treatment.
The possibility of systemic factors such as hypothyroidism, coagulopathy or
thrombophilia, or immunologic factors (e.g., lupus anticoagulant) as a cause of
recurrent losses should be evaluated when there is reason for clinical suspicion
or other evaluations have proven inconclusive. When immunologic factors are present,
the use of low-dose aspirin and subcutaneous heparin (5000 units twice daily) has
reduced the rate of subsequent loss.
The evaluation of patients with recurrent pregnancy losses starts with a history
and physical examination with an eye toward cervical incompetence, drug or
chemical exposures, gastrointestinal diseases, a family history of miscarriages,
birth defects, or thrombosis. The history and physical examination often direct
the appropriate laboratory evaluation, including studies of thyroid-stimulating
hormone and antithyroid antibodies, or a thrombophilia profile. If all these tests
are normal, an evaluation of the uterine cavity by sonohysterography or hysteroscopy
should be considered. It is not necessary to obtain endometrial bacteriologic cultures
or perform human leukocyte antigen typing of the woman or her partner.
Therapeutic intervention for recurrent pregnancy loss is always based on the underlying cause. Progesterone and thyroid supplements have not been shown to reduce the risk of pregnancy loss.
