Spontaneous Abortion

Essentials of Diagnosis

• Suprapubic pain, uterine cramping, and/or back pain.
  
• Vaginal bleeding.
  
• Cervical dilatation.
  
• Extrusion of products of conception.
  
• Disappearance of symptoms and signs of pregnancy.
  
• Negative pregnancy test or quantitative β-hCG that is not properly increasing.
  
• Abnormal ultrasound findings (eg, empty gestational sac, fetal disorganization, lack of fetal growth).

General Considerations

Spontaneous abortion is the most common complication of pregnancy. It is defined as delivery occurring before the 20th completed week of gestation. It implies delivery of all or any part of the products of conception, with or without a fetus weighing less than 500 grams. Threatened abortion is bleeding of intrauterine origin occurring before the 20th completed week, with or without uterine contractions, without dilatation of the cervix, and without expulsion of the products of conception. Complete abortion is the expulsion of all of the products of conception before the 20th completed week of gestation, while incomplete abortion is the expulsion of some, but not all, of the products of conception. Inevitable abortion refers to bleeding of intrauterine origin before the 20th completed week, with dilatation of the cervix without expulsion of the products of conception. In missed abortion, the embryo or fetus dies in utero, but the products of conception are retained in utero. In septic abortion, infection of the uterus and sometimes surrounding structures occur.

Incidence

Although the true incidence of spontaneous abortion is unknown, approximately 15% of clinically evident pregnancies and 60% of chemically evident pregnancies end in spontaneous abortion. Eighty percent of spontaneous abortions occur prior to 12 weeks' gestation.

The incidence of abortion is influenced by the age of the mother and by a number of pregnancy-related factors, including whether a previous full-term normal pregnancy has occurred, the number of previous spontaneous abortions, whether there has been a previous stillbirth, and whether a previous infant was born with malformations or known genetic defects. Additionally, parental influences, including balanced translocation carriers and medical complications, may influence the rate of spontaneous abortion.