Abortion: Types and Incidence

Abortion

• Abortion is the expulsion of a fetus from the uterus before it reaches viability (around 20th week of gestation).

Spontaneous Abortion

• Spontaneous abortion is a termination of pregnancy without any action taken by the woman or another person.
• Incidence of spontaneous abortion is approximately 18% to 31% of all pregnancies.
• Most pregnancies (50% to 70%) are lost during the first trimester, many of which may occur before implantation or during the first month after the last menstrual period.

Causes of Spontaneous Abortion

• Chromosomal abnormalities (50%-60%) resulting in anembyonic pregnancies.
• Maternal infections such as Syphilis, Listeriosis, Toxoplasmosis, Brucellosis, Rubella, and Cytomegalic Virus.
• Maternal endocrine disorders such as Hypothyroidism, Diabetes, and decreased Progesterone.
• Anatomic defects of the uterus, uterine septum, or cervical incompetence.
• Heavy alcohol consumption and heavy smoking may contribute to spontaneous abortion.
• Teratogen drugs and radiation (cancer chemotherapy) can also cause spontaneous abortion.

Pathophysiology of Spontaneous Abortion

• Embryonic death occurs, leading to a decrease in human chorionic gonadotropin (hCG) and progesterone and estrogen levels.
• The uterine decidua is sloughed off, resulting in vaginal bleeding, and the embryo/fetus is expelled.

Classification of Spontaneous Abortion

• Threatened Abortion: unexplained bleeding, cramping, or backache indicating that the fetus may be in jeopardy, with bleeding persisting for days and the cervix remaining closed.
• Inevitable Abortion: abortion is usually inevitable when membranes rupture and the cervix dilates, resulting in excessive bleeding or infection.
• Incomplete Abortion: some but not all of the products of conception are expelled from the uterus, with active uterine bleeding and severe abdominal cramping.
• Complete Abortion: all products of conception are expelled from the uterus, with uterine contractions and bleeding subsiding, and the cervix closing.
• Missed Abortion: the fetus dies in utero but is not expelled, resulting in uterine growth ceasing, breast changes regressing, and a negative pregnancy test.
• Recurrent or Habitual Abortion: abortion occurs consecutively in three or more pregnancies, with causes including genetic or chromosomal abnormalities, reproductive tract anomalies, and inadequate luteal phase.

Learn about the different types of abortion, including spontaneous abortion, and understand the incidence rates associated with these occurrences. Explore the etiology and factors influencing spontaneous abortions.