Description

• Miscarriage, also known as early pregnancy loss (EPL) or spontaneous abortion (SAb), is the failure or loss of a pregnancy before 13 weeks’ gestational age (WGA).
• Related terms
  • Anembryonic gestation: gestational sac on ultrasound (US) without visible embryo after 6 WGA
  • Complete abortion: entire contents of uterus expelled
  • Ectopic pregnancy: pregnancy outside the uterus
  • Embryonic or fetal demise: cervix closed; embryo or fetus present in the uterus without cardiac activity
  • Incomplete abortion: abortion with retained products of conception, generally placental tissue
  • Induced or therapeutic abortion: evacuation of uterine contents or products of conception medically or surgically
  • Inevitable abortion: cervical dilatation or rupture of membranes in the presence of vaginal bleeding
  • Recurrent abortion: three or more consecutive pregnancy losses at <15 WGA
  • Threatened abortion: vaginal bleeding in the 1st trimester of pregnancy
  • Septic abortion: a spontaneous or therapeutic abortion complicated by pelvic infection; common complication of illegally performed induced abortions
• Synonym(s): SAb
  • Missed abortion and blighted ovum are used less frequently in favor of terms representing the sonographic diagnosis.

Epidemiology

Predominant age: increases with advancing age, especially >35 years; at age 40 years, the loss rate is twice that of age 20 years.

Incidence

• Threatened abortion (1st-trimester bleeding) occurs in 20–25% of clinical pregnancies.
• Between 10% and 15% of all clinically recognized pregnancies end in EPL, with 80% of these occurring within 12 weeks after last menstrual period (LMP) (1).
• When both clinical and biochemical (β-hCG detected) pregnancies are considered, about 30% of pregnancies end in EPL.
• One in four people with a uterus will have an EPL during their lifetime (1).

Etiology and Pathophysiology

Chromosomal anomalies (50% of cases), congenital anomalies, trauma, maternal factors: uterine abnormalities, infection (toxoplasma, other viruses, rubella, cytomegalovirus, herpesvirus), maternal endocrine disorders, hypercoagulable state

Genetics
Approximately 50% of 1st-trimester EPLs have significant chromosomal anomalies, with 50% of these being autosomal trisomies and the remainder being triploidy, tetraploidy, or 45X monosomies.

Risk Factors

Most cases of EPL occur in patients without identifiable risk factors; however, risk factors include the following: chromosomal abnormalities, advancing maternal age, uterine abnormalities, and maternal chronic disease (antiphospholipid antibodies, uncontrolled diabetes mellitus, polycystic ovarian syndrome, obesity, hypertension, thyroid disease, renal disease); other possible contributing factors include smoking, alcohol intake, cocaine use, infection, and luteal phase defect.

General Prevention

• Insufficient evidence supports the use of aspirin and/or other anticoagulants, bed rest, hCG, immunotherapy, uterine muscle relaxants, or vitamins for general prevention of EPL, before or after threatened abortion is diagnosed.
• By the time the hemorrhage begins, half of pregnancies complicated by threatened abortion already have no fetal cardiac activity.
• In threatened abortion, oral progestogens may reduce the risk of EPL (RR 0.73, 95% CI 0.59–0.92) and possibly increase the rate of live birth (RR 1.07, 95% CI 1–1.15).
• Antiphospholipid syndrome: The combination of unfractionated heparin and aspirin reduces risk of EPL in women with antiphospholipid antibodies and a history of recurrent abortion.