Januari 4, 2008
Synonyms and related keywords: miscarriage, blighted ovum, anembryonic pregnancy, fetal demise, spontaneous abortion, missed abortion, threatened abortion, complete abortion, incomplete abortion, inevitable abortion, pregnancy loss, utero death of the embryo, utero death of the fetus, chromosomal anomalies, septate uterus, luteal phase insufficiency, hypothyroidism, hypoprolactinemia, polycystic ovarian syndrome, anembryonic pregnancy, subchorionic hematoma, subchorionic hemorrhage, subchorionic bleeding, endovaginal ultrasound, transabdominal ultrasounds
Background: The most common complication of pregnancy is spontaneous abortion. Spontaneous abortion is categorized as threatened, inevitable, incomplete, complete, or missed. Abortion can be categorized further as sporadic or recurrent. By definition, a missed abortion is in utero death of the embryo or fetus before the 20th week of gestation with retained products of conception. Missed abortions also may be referred to as blighted ovum, anembryonic pregnancy, or fetal demise.
Pathophysiology: The timing of a spontaneous abortion suggests its pathophysiology. Genetic anomalies (trisomies); hormonal abnormalities; and infectious, immunologic, and environmental factors usually result in first-trimester loss. Anatomic factors usually are associated with second-trimester loss.
- In the US: Many pregnancies are not viable, with an estimated loss of 50% before the first missed menstrual period. These pregnancies usually are not clinically recognized. Classic spontaneous abortion is defined as a clinically recognized (ie, by blood test, ultrasound) pregnancy loss before the 20th week of gestation. Estimates place frequency at 10-15% of pregnancies.
- Internationally: A report from the United Kingdom by Pandya utilizing ultrasound screening at 10-13 weeks of gestation revealed 2.8% of pregnancy failure with 62.5% missed abortions and 37.5% anembryonic pregnancies. The prevalence was higher in women with a history of vaginal bleeding.
Mortality/Morbidity: Surveillance data of pregnancy-related deaths from 1987 through 1990 revealed a total of 1459 deaths in the US. Of these deaths, spontaneous and induced abortions accounted for 5.6%.
Race: Surveillance data for pregnancy-related deaths (1987-1990) demonstrated more deaths followed ectopic pregnancy and spontaneous and induced abortion among African American women than among Caucasian women. Fourteen percent of pregnancy-related deaths among black women were due to ectopic pregnancies; 7% were due to abortions. Among white women, data showed that 8% of pregnancy-related deaths were due to ectopic pregnancies; 4% were due to abortions.
- Age and increased parity affect a woman’s risk of miscarriage. In women younger than 20 years, miscarriage occurs in an estimated 12% of pregnancies. In women older than 20 years, miscarriage occurs in an estimated 26% of pregnancies.
- Age primarily affects the oocyte. When oocytes from young women are used to create embryos for transfer to older recipients, implantation rates and pregnancy rates mimic those seen in younger women; the number of miscarriages and chromosomal anomalies decreases, suggesting that the uterus is not responsible for poor outcomes in women of advanced reproductive age
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