Anembryonic Pregnancy

Excerpt

An anembryonic pregnancy is characterized by a gestational sac that forms and grows while an embryo fails to develop. Although the terms anembryonic pregnancy and blighted ovum are synonymous, the latter is falling out of favor with the more descriptive former term. Anembryonic pregnancy constitutes a significant but unknown proportion of miscarriages, with the American Pregnancy Association estimating anembryonic pregnancy to constitute half of all first-trimester miscarriages. Approximately 15% of all clinically recognized pregnancies end in first-trimester loss, with live births occurring in only 30% of all pregnancies. Many patients with early pregnancy loss (including anembryonic pregnancies) are unaware of their miscarriage, particularly when the loss occurs in the early stages of pregnancy.

Early Pregnancy Loss

In the first trimester, the terms early pregnancy loss, miscarriage, or spontaneous abortion are often used interchangeably. Early pregnancy loss is defined as the spontaneous loss of a pregnancy before 13 weeks of gestation.

Miscarriage

The World Health Organization (WHO) and the Centers for Disease Control and Prevention (CDC) define miscarriage as the loss of a pregnancy before 20 weeks of gestation or the ejection or removal of an embryo or fetus that weighs ≤500 g. This definition in the United States may vary based on state laws.

Biochemical Miscarriage

Biochemical miscarriage is a loss that occurs after a positive urine pregnancy test (hCG) or a raised serum beta-hCG before ultrasound or histological verification and confirmation.

Clinical Miscarriage

Clinical miscarriage is diagnosed when ultrasound examination or histologic evidence has confirmed the existence of an intrauterine pregnancy. Clinical miscarriage is classified as early (before 12 weeks of pregnancy) and late (12 to 20 weeks of pregnancy).