Classification and Differential Diagnosis of Spontaneous Abortions
Because the differential diagnosis of bleeding in the first trimester of pregnancy includes a wide range of possibili-ties, such as ectopic pregnancy, hydatidiform mole, cervi-cal polyps, cervicitis, and neoplasm, the patient should be examined whenever there is bleeding in early pregnancy.
Threatened abortion is characterized by bleeding in thefirst trimester without loss of fluid or tissue. About half of women with a threatened abortion proceed to spontaneous abortion. Those who carry to viability a pregnancy compli-cated by threatened abortion are at greater risk for preterm delivery and an infant of low birth weight. There does not, however, appear to be a higher incidence of congenital malformations in these newborns. Some patients describe bleeding at the time of their expected menses, sometimes referred to as implantation bleeding, which may be re-lated to implantation of the embryo in the endometrium.
In cases of miscarriage, bleeding usually begins first, and cramping abdominal pain follows a few hours to several days later. The pain may present as anterior and clearly rhythmic cramps; as a persistent low backache, as-sociated with a feeling of pelvic pressure; or as a dull, mid-line, suprapubic discomfort. The combination of bleeding and pain usually indicates a poor prognosis for pregnancy continuation.
Ectopic pregnancy should always be considered in the differ-ential diagnosis of threatened abortion.
An inevitable abortion is the gross rupture of the membranes in the presence of cervical dilation. Typically, uterine contractions begin promptly, resulting in expul-sion of the products of conception. It is unusual for a preg-nancy to successfully reach viability in this circumstance. Conservative management of these patients significantly increases the risk of maternal infection.
During an incomplete abortion, the internal cervical os opens and allows passage of blood. The products of con-ception may remain entirely in utero or may partially ex-trude through the dilated os. Before 10 weeks, the fetus and placenta are commonly expelled together, but later they are delivered separately. In many cases, retained placental tis-sue remains in the cervical canal, allowing easy extraction from an exposed external os with ring forceps. If unsuccess-ful, a suction curettage effectively evacuates the uterus.
Complete abortion refers to a documented preg-nancy that spontaneously passes all of the products of con-ception. Before 10 weeks, the fetus and placenta are often expelled in toto.
missed abortion is the retention of a failed intra-uterine pregnancy for an extended period, usually defined as more than two menstrual cycles. These patients have an absence of uterine growth and may have lost some of the early symptoms of pregnancy.
Many women have no symptoms during this period except persistent amenorrhea. If the missed abortion ter-minates spontaneously, and most do, the process of expul-sion is the same as in any abortion.
Recurrent pregnancy loss is a term used when a patienthas had more than two consecutive pregnancy losses. The timing of the pregnancy losses may provide a clue to their cause. Genetic factors most frequently result in early em-bryonic losses, whereas autoimmune or anatomic abnor-malities are more likely to result in second-trimester losses. Karyotyping is recommended for both parents when re-current early abortion occurs, because there is a 3% chance that one parent is a symptomless carrier of a genetically balanced chromosomal translocation.
When recurrent pregnancy losses occur later than the first trimester of pregnancy, they can be caused by maternal medical conditions or anatomic anomalies, which may be treatable. Uterine anomalies, such as septate uteri, can be related to fetal wastage. In these cases, management includ-ing hysterography, operative hysteroscopy, or laparoscopy may be required to correct the problem. Intrauterine synechiae associated with Asherman syndrome may occur after a curettage procedure has denuded the endometrium past the layer of the basalis, so that webs of scar tissue de-velop across the uterine cavity (the synechiae). Asherman syndrome is associated with amenorrhea or irregular menses, infertility, and recurrent pregnancy loss. The diag-nosis is confirmed by a hysterogram that shows the charac-teristic webbed pattern or by hysteroscopy. Treatment involves lysis of the synechiae and postoperative treatment with high doses of estrogen to facilitate endometrial prolif-eration, leading to the reestablishment of a normal endome-trial layer.
Much attention has focused on the immune system and its role in recurrent pregnancy loss. Antiphospho-lipid antibodies are a family of autoantibodies that bindto negatively charged phospholipids. Lupus anticoagulant and anticardiolipin antibody have been linked with exces-sive pregnancy wastage. Treatment may include low-dose aspirin along with unfractionated heparin This therapy, begun when pregnancy is diagnosed, may be continued until delivery. Other immunologic defects associated with recurrent miscarriage are factor V Leiden defect and pro-thrombin gene mutation.