Subchorionic Hematoma and Pregnancy Risks

Condition Characterized by Partial Placental Detachment

Pregnant African American mother holding her stomach in bed
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A subchorionic hematoma is the abnormal accumulation of blood between the placenta and the wall of the uterus. Scientists do not know exactly why this occurs, but, in some cases, it may be caused the physical disruption of placental tissues or the abnormal attachment of the fertilized egg during implantation.

While a condition like this could understandably cause alarm, it shouldn't suggest that you will lose your baby.

In fact, if the hematoma is small, develops during early pregnancy, and is otherwise symptom-free, the chance of carrying your baby to term is good.

A subchorionic hematoma is not an entirely uncommon situation, with some studies suggesting rates as high as 22 percent among all pregnancies while others peg it as low as 0.5 percent.

Symptoms of Subchorionic Hematoma

A woman with a subchorionic hematoma may experience bleeding, ranging from light spotting to a heavy flow with clots. Cramping is also common. Others, meanwhile, will have no symptoms. In fact, many subchorionic hematomas are only found during a routine ultrasound test.

Vaginal bleeding is estimated to affect as many as one in four women during the first half of a pregnancy and is a common reason for first-trimester ultrasonography.

Risk of Complications

A subchorionic hematoma can increase the risk of pregnancy complications like miscarriage, preterm labor, placental abruption, and the premature rupture of membranes.

The risk is largely related to the size of the hematoma, the gestational age of the fetus, and the mother's age.

By and large, hematomas found during the early part of the first trimester are less problematic than those discovered later in the first or second trimester. Not all hematoma will grow in size (and some even regress) but those that do may partially strip away the placenta from its attachment site on the uterus.

If it strips away more than 30 percent, the hematoma can grow even larger, causing the premature rupture of membranes and leading to a spontaneous abortion.

Generally speaking, small hematomas on the surface of the placenta are far less concerning than those that develop under the placenta or behind the fetal membrane.

From a statistical standpoint, a subchorionic hematoma is associated with a relatively low risk of preterm birth compared to women without a hematoma. By contrast, a hematoma can increase the risk of the premature rupture of membranes by 61 percent and placental abruption by more than 300 percent, according to research from the Department of Obstetrics and Gynecology at Washington University in St. Louis.

Treatment Options

Sadly, there is not much one can do if a subchorionic hematoma is diagnosed. Depending on the location and size of the hematoma, a doctor may advise you to come in for regular follow-ups but to otherwise avoid strenuous activity, heavy lifting, or excessive exercise. Rest is usually recommended to avoid increases in blood pressure, while ample hydration can help prevent constipation and the subsequent straining that can increase bleeding.

Less commonly, a doctor may recommend the use of blood thinners to bleed the clot out.

If the chances of miscarriage are high, some doctor will use estrogen and progesterone therapy to slow or prevent further hemorrhaging.

Sources:

Palatnik, A. and Grobman, W. "The relationship between first-trimester subchorionic hematoma, cervical length, and preterm birth." Am J Obstet Gynecol. 2015; 213(3):403.e1-4. DOI: 10.1016/j.ajog.2015.05.019.

Tuuli, M.; Norman, S.; Odibo, A. et al. "Perinatal outcomes in women with subchorionic hematoma: a systematic review and meta-analysis." Obstet Gynecol, 2011; 117(5):1205-12. DOI: 10.1097/AOG.0b013e31821568de.