Dear Doctors: Can you please talk about placenta accreta? It happened to my sister, and she had serious medical issues when she had her baby. How can you know that you have it? Does it run in families? My husband and I are ready to start our own family, but this has me scared.
Dear Reader: Let's begin with the placenta, which is a temporary organ that forms in the uterus over the course of a pregnancy. It serves as the medium through which oxygen and nutrients pass from the mother to the developing baby. The placenta also performs a wide range of complex functions that, once the baby is born, will be carried out by other organs and structures. These include the lungs, liver, gastrointestinal tract, kidneys and endocrine system.
During the first trimester of pregnancy, the placenta forms gradually. In the second trimester, its growth parallels that of the baby. Although it continues to develop in the third trimester, its growth slows significantly. By the time the baby reaches full term, the placenta is a spongy disc of tissue 8 to 10 inches in diameter, about an inch thick and weighs about 18 ounces. In order for a pregnancy to be successful, and to result in a safe delivery, proper development of the placenta is essential. This includes not only the physiological structure of the organ, but also its position and placement within the uterus.
The term placenta accreta refers to a serious pregnancy complication in which the placenta becomes too deeply attached to the wall of the uterus. This can lead to a preterm delivery, and it can cause excessive bleeding during pregnancy, labor and following the birth. The degree of penetration into the lining of the uterine wall can prevent the smooth separation of the organ that occurs during delivery in a normal pregnancy.
A hysterectomy is often required to save the mother's life. Risk factors include previous cesarean section, previous uterine surgery and older maternal age. There is no evidence of a genetic component, or that the condition runs in families.
Placenta accreta often occurs without symptoms. In some cases, it can cause certain changes to maternal blood profiles, but these are not reliable indicators. A study published in 2020 suggests there may a biomarker associated with the condition. However, more research is needed for this to be developed into a test. As a result, there is no blood test for the condition at this time. It can sometimes be spotted in the course of imaging studies, most often with an ultrasound.
Due to the cycle of placental growth that we described, diagnosis commonly takes place in the second or third trimester of pregnancy. When the condition is discovered, a planned C-section is often recommended. If someone is at risk of placenta accreta, it is recommended they seek care with an OB-GYN with experience in the condition and plan delivery in a facility with a robust blood bank. For women at risk, the National Accreta Foundation (preventaccreta.org) is a good resource.
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