Second Trimester Complications that May Cause Miscarriage: Incompetent Cervix, Placenta Abruption, and Prenatal Testing
© Mischele Lewis
After you pass the first trimester, the risk of miscarriage lessens but is not eliminated. Later miscarriages may result from an infection or an abnormality in the uterus or in the placenta.
An incompetent cervix is a cervix that is softer and weaker than normal. It may shorten and dilate as the weight of a growing baby puts pressure on it, causing second trimester miscarriage, premature rupture of the fetal membranes, or pre-term delivery.
Doctors have no foolproof method of diagnosing cervical incompetence; often, the only clues come from a patient's clinical history. You could have an increased risk of incompetent cervix if you've had a second trimester miscarriage or pre-term labor with minimal or no uterine contractions.
Watch carefully for increased vaginal discharge, spotting, pelvic pressure, or menstrual-like cramping or "heaviness." If you have any of these symptoms, contact your doctor immediately, because it could mean that your cervix is changing.
As treatment, your doctor may recommend a cerclage - a precautionary surgical procedure usually done in the late first or early second trimester. Under anesthesia, a doctor will place a strong stitch around the cervix in an attempt to reinforce it. Afterward, you may need to avoid strenuous activity or be on bedrest until the baby is full term.
Placenta Abruption
Another second trimester complication is placenta abruption, where the placenta separates from the uterus prematurely. It is more common in mothers-to-be who smoke, abuse drugs or alcohol, have had an accident, and in mothers who are older, have hypertension, or took aspirin late in pregnancy.
Bleeding is the main sign of placenta abruption, and it varies depending on the severity of the separation. Other signs include cramping and uterine tenderness.
There is no clear-cut cause of abruption. When the separation is minor, bedrest usually stops the bleeding. In severe cases where more than half the placenta separates, it can cause fetal demise and miscarriage if caught too late. If the separation occurs late in the second trimester or in the third, sometimes delivering the baby can prevent the loss of a child, but not always.
Prenatal Testing and Miscarriage
Unfortunately, two important prenatal tests - amniocentesis and chorionic villus sampling (CVS) - can raise your risk of miscarriage. Amniocentesis, usually performed at 15-18 weeks, causes one miscarriage in about every 200 women. CVS, done at 10-12 weeks, is twice as likely to result in miscarriage. These tests may be done if an Alpha Fetal Protein (AFP) blood test is abnormal and shows the potential for birth defects.
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