Up to 15% of all pregnancies and about 30% of all first pregnancies end in spontaneous abortion (miscarriage). At least 75% of miscarriages occur during the first trimester.
Causes
Spontaneous abortion may result from fetal, placental, or maternal factors.
Spontaneous abortion may result from fetal, placental, or maternal factors.
Fetal factors usually cause abortions before the 12th week of gestation and include:
- defective embryologic development resulting from abnormal chromosome division (most common cause of fetal death)
- faulty implantation of the fertilized ovum
- failure of the endometrium to accept the fertilized ovum.
- premature separation of the normally implanted placenta
- abnormal placental implantation.
- maternal infection, severe malnutrition, and abnormalities of the reproductive organs (especially an incompetent cervix, in which the cervix dilates painlessly and bloodlessly in the second trimester)
- endocrine problems, such as thyroid dysfunction or a luteal phase defect
- trauma, including any surgery that requires manipulation of the pelvic organs
- phospholipid antibody disorder
- blood group incompatibility
- drug ingestion.
Signs and symptoms
Prodromal signs of spontaneous abortion include a pink discharge for several days or a scant brown discharge for several weeks before the onset of cramps and increased vaginal bleeding. For a few hours, the cramps intensify and occur more frequently; then the cervix dilates to expel uterine contents. If the entire contents are expelled, cramps and bleeding subside. However, if any contents remain, cramps and bleeding continue.
Prodromal signs of spontaneous abortion include a pink discharge for several days or a scant brown discharge for several weeks before the onset of cramps and increased vaginal bleeding. For a few hours, the cramps intensify and occur more frequently; then the cervix dilates to expel uterine contents. If the entire contents are expelled, cramps and bleeding subside. However, if any contents remain, cramps and bleeding continue.
Diagnosis
Diagnosis of spontaneous abortion is based on clinical evidence of expulsion of uterine contents, pelvic examination, and laboratory studies. Human chorionic gonadotropin in the blood or urine confirms pregnancy.
Diagnosis of spontaneous abortion is based on clinical evidence of expulsion of uterine contents, pelvic examination, and laboratory studies. Human chorionic gonadotropin in the blood or urine confirms pregnancy.
Pelvic examination determines the size of the uterus and whether this size is consistent with the length of the pregnancy. Tissue pathology indicates evidence of products of conception. Blood loss is rarely significant enough to decrease hemoglobin levels.
Treatment
An accurate evaluation of uterine contents is necessary before a plan of treatment can be formulated. The progression of spontaneous abortion can’t be prevented. If bleeding is severe, a transfusion with packed red blood cells or whole blood is required. Initially, I.V. administration of oxytocin stimulates uterine contractions. If any remnants remain in the uterus, dilatation and curettage or dilatation and evacuation should be performed.
Dilation and evacuation is also performed in first- and second-trimester therapeutic abortions. Medical abortion, using mifepristone (RU-486) and misoprostol (a prostaglandin) is also effective (90% to 97%) for pregnancy termination less than 49 days from the last menses.
An accurate evaluation of uterine contents is necessary before a plan of treatment can be formulated. The progression of spontaneous abortion can’t be prevented. If bleeding is severe, a transfusion with packed red blood cells or whole blood is required. Initially, I.V. administration of oxytocin stimulates uterine contractions. If any remnants remain in the uterus, dilatation and curettage or dilatation and evacuation should be performed.
Dilation and evacuation is also performed in first- and second-trimester therapeutic abortions. Medical abortion, using mifepristone (RU-486) and misoprostol (a prostaglandin) is also effective (90% to 97%) for pregnancy termination less than 49 days from the last menses.
After an abortion, spontaneous or induced, an Rh-negative female with a normal indirect Coombs’ test result should receive Rho(D) immune globulin (human) to prevent further Rh isoimmunization.
In a patient who has suffered from habitual abortion, spontaneous abortion can result from an incompetent cervix. Treatment involves bed rest and, in some situations, surgical reinforcement of the cervix 12 to 14 weeks after the last menses. A few weeks before the estimated delivery date, the sutures are removed and the patient awaits the onset of labor. An alternative procedure, especially for a woman who wants to have more children, is to leave the sutures in place and to deliver the infant by cesarean birth.
In a patient who has suffered from habitual abortion, spontaneous abortion can result from an incompetent cervix. Treatment involves bed rest and, in some situations, surgical reinforcement of the cervix 12 to 14 weeks after the last menses. A few weeks before the estimated delivery date, the sutures are removed and the patient awaits the onset of labor. An alternative procedure, especially for a woman who wants to have more children, is to leave the sutures in place and to deliver the infant by cesarean birth.
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