Retained Products of Conception: What You Need to Know

The term retained products of conception refers to a situation in which tissue related to pregnancy, such as fetal membranes or parts of the placenta, remains in uterus after delivery. The situation also can occur after spontaneous abortion (miscarriage), termination of pregnancy (elective abortion), and other situations, such as missed abortion, incomplete abortion, and stillbirth. Just to remind you of the meaning of all of these terms, a continuum of situations, consisting of threatened abortion, inevitable abortion, complete abortion, incomplete abortion, and missed abortion, all fall within the realm of spontaneous abortion, which applies to pregnancy loss occurring prior to a gestational age of 20 weeks, the halfway point of pregnancy. Beyond 20 weeks, pregnancy loss is called a stillbirth, yet often the colloquial miscarriage is applied to pregnancy loss beyond 20 weeks, at least through the second trimester, which ends at the close of the 26th gestational week. threatened abortion. This part of the spectrum technically is not a kind of pregnancy loss, because it only means that a spontaneous abortion is gearing up to occur but may not. There is a threat that it may occur because there are symptoms (pain and/or bleeding) and on ultrasound it looks as though the uterus is getting ready to expel the products of conception. But there is time to intervene with the possibility of preventing the expulsion, because the cervical os, the passageway between the uterus and the vagina, remains closed.

Next on the spectrum is an inevitable abortion, which we can include within the realm of pregnancy loss, since inevitable means that the abortion will happen no matter what, because the cervical os is open.

Missed abortion means that the embryo or fetus is no longer viable, but the uterus forgot to expel it. An incomplete abortion is when the embryo or fetus becomes non-viable and is only partly expelled. Pieces are retained, but even in the case of complete spontaneous abortion, bits of pregnancy related tissue may remain in the uterus, just as bits of pregnancy-related tissue can remain in the uterus after a normal birth, after a stillbirth, or after an elective abortion. In all of these cases, the retained products of conception can cause an infection of the uterus, such as endometritis. If the products of conception do not come out on their own soon, doctors need to intervene, medically or surgically, to remove them. An abortion that causes an infection is called a septic abortion (term that can apply either to a spontaneous abortion or an induced abortion, as either can become infected).

One major factor putting a pregnant woman at risk for retained products of conception is placenta accreta. This is a condition in which the placenta is attached too deeply into the uterus, making it difficult to separate from the uterine wall after delivery. Normally, the placenta is attached only through the endometrium, the innermost layer of uterus. In placenta accreta, however, the placenta reaches through the endometrium and is up against the myometrium (the muscular layer of the uterus) or penetrates the myometrium. The condition is subcategorized based on how deep the penetration goes. During and following delivery of the baby, placenta accreta can cause severe bleeding, while also elevating the risk of uterine rupture. This is because, when the placenta does finally separate from the placenta, it can take parts of the myometrium with it. Risk factors for placenta accreta include a previous placenta accreta, previous cesarean delivery, uterine surgery, and multiple gestation. Typically, the condition is diagnosed through ultrasound and in such cases, doctors will plan for a cesarean birth. In cases of hemorrhage, the mother can be treated with medications to control bleeding, intravenous fluids, and, if needed, transfusion of blood products. In severe cases, doctors may need to perform a cesarean hysterectomy, meaning that the baby is delivered surgically, and the uterus is removed.

Even when a pregnant woman suffers no symptoms suggestive of retained products of conception, such products may remain within her uterus. The condition can present with vaginal bleeding that does not improve over time, pelvic or lower abnormal pain, vaginal discharges, and fever, if the condition causes infection. While your obstetrician may suspect retained products of conception, the diagnosis may be confirmed with ultrasound examination.

Management of retained products of conception usually consists of surgical removal of the retained products. This is done usually by way of what doctors call dilation and curettage. This means dilating the cervix, so that the doctor can pull out the products through the cervix, usually with a vacuum aspiration and curettage. Typically, this procedure will be performed under general anesthesia. Two potential complications of the procedure are endometritis (infection of the endometrium) and Asherman syndrome, in which adhesions (scar tissue) form in the uterus. Curettage of the endometrium also can damage the basal layer of the endometrium, causing adhesions when the damaged tissue heals. The adhesions can connect different parts of the uterus together that are not supposed to be connected. These parts can include walls of the uterus attaching together or the inner lining of the cervix, causing the cervix to close. This can lead to amenorrhea and infertility.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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