In spontaneous abortion, hemorrhage into the decidua basalis often occurs. Necrosis and inflammation appear in the area of implantation. The pregnancy becomes partially or entirely detached. Uterine contractions and dilatation of the cervix result in expulsion of most or all of the products of conception.
A. Threatened Abortion
At least 20% of pregnant women have some first trimester bleeding. In most cases, this is thought to represent an implantation bleed. The cervix remains closed and slight bleeding with or without cramping may be noted.
B. Inevitable Abortion
Abdominal or back pain and bleeding with an open cervix indicate impending abortion. Abortion is inevitable when cervical effacement, cervical dilatation, and/or rupture of the membranes is noted.
C. Incomplete Abortion (
In incomplete abortion the products of conception have partially passed from the uterine cavity. In gestations of less than 10 weeks’ duration, the fetus and placenta are usually passed together. After 10 weeks, they may be passed separately with a portion of the products retained in the uterine cavity. Cramps are usually present. Bleeding generally is persistent and is often severe.
D. Complete Abortion (
Complete abortion is identified by passage of the entire conceptus. Slight bleeding may continue for a short time, although pain usually ceases.
E. Missed Abortion
Missed abortion implies that the pregnancy has been retained following death of the fetus. It is not known why the pregnancy is not expelled. It is possible that normal progestogen production by the placenta continues while the estrogen levels fall, which may reduce uterine contractility.
F. Blighted Ovum
Blighted ovum or anembryonic pregnancy represents a failed development of the embryo, so that only a gestational sac, with or without a yolk sac, is present.
Revision date: June 11, 2011
Last revised: by Janet A. Staessen, MD, PhD