What causes placenta previa

Mar 21, 2025 Source: Cainiu Health

Dr. Zhang Lu

Introduction

Under normal circumstances, placenta previa is caused by factors such as excessive placental size, delayed development of the fertilized egg's trophoblast, endometritis, endometrial injury or lesions, uterine septum, and others. When the placenta is excessively large, as in twin pregnancies or with a succenturiate lobe, the placenta tends to extend into the lower segment of the uterus, thus forming placenta previa. Prenatal examinations should be strengthened, and vaginal bleeding should be closely monitored.

Generally, placenta previa is caused by an overly large placental area, delayed development of the fertilized egg's trophoblast, endometritis, endometrial injury or lesions, uterine septum, and other factors. The solution depends on the specific cause and requires prompt medical attention and treatment according to medical advice. Details are as follows:

1. Large placental area: When the placenta is excessively large, such as in twin pregnancies or with a succenturiate lobe, the placenta may extend into the lower segment of the uterus, resulting in placenta previa. Prenatal checkups should be intensified, and vaginal bleeding should be closely monitored. During expectant management, nutrition should be enhanced, and anemia corrected.

2. Delayed development of the fertilized egg's trophoblast: When the fertilized egg reaches the uterine cavity before the trophoblast has developed sufficiently for implantation, it continues to move downward and implants in the lower uterine segment, resulting in placenta previa. Pregnant women should maintain a pleasant mood, avoid anxiety and stress, and undergo regular prenatal examinations to monitor fetal growth and development.

3. Endometritis: Endometritis can affect the implantation and development of the fertilized egg, leading to abnormal placental positioning and placenta previa. It may also cause lower abdominal pain. Anti-inflammatory treatment should be administered as directed by a physician, including medications such as Roxithromycin Capsules, Cefuroxime Axetil Granules, and Azithromycin Tablets.

4. Endometrial injury or lesions: Endometrial damage or disease can impair the endometrium and lead to poor formation of decidual blood vessels, causing insufficient placental blood supply. To obtain adequate nutrition, the placenta enlarges and extends into the lower uterine segment, resulting in placenta previa, which may also be accompanied by anemia. Treatment should be guided by a physician using medications such as Salbutamol Sulfate Tablets, Magnesium Sulfate Injection, and Nifedipine Sustained-Release Tablets.

5. Uterine septum: A uterine septum can interfere with normal placental attachment, causing the placenta to extend toward or even cover the cervix, resulting in placenta previa. In addition to the bleeding symptoms of placenta previa, patients may also experience abdominal discomfort. Treatment should follow medical advice and may involve hysteroscopic surgical resection, which can reduce the risk of miscarriage and improve live birth rates.

Pregnant women with high-risk factors should rest adequately during pregnancy, avoid strenuous exercise and sexual activity, and undergo regular prenatal checkups to detect and manage placenta previa promptly.

References:

[1] Xie Xing, Kong Beihua, Duan Tao. Obstetrics and Gynecology (9th Edition) [M]. Beijing: People's Medical Publishing House, 2018.

[2] Obstetrics Group, Chinese Society of Obstetrics and Gynecology, Chinese Medical Association. Clinical Diagnosis and Management Guidelines for Placenta Previa (2020 Edition) [J]. Chinese Journal of Obstetrics and Gynecology, 2020.

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