Patient's question:
NoDoctor's answer:
Placenta previa, also known as placenta previa. The normal attachment site of the placenta is on the posterior, anterior, or lateral wall of the uterine body. If the placenta is attached to the lower segment of the uterus or covers the internal cervical os, and its position is lower than the presenting part of the fetus, it is called placenta previa. Placenta previa is one of the main causes of bleeding in late pregnancy and a serious complication of pregnancy. If not properly managed, it can endanger the life safety of both the mother and the fetus. Its incidence rate is 1:55 to 1:200, and it is more common in multiparous women, especially those with multiple births.### I. Etiology
The exact cause has not yet been clearly identified. It may be related to the following factors:
① Incomplete endometrium. Postpartum infection, multiple births, IUD insertion, multiple curettage procedures, and cesarean sections can lead to endometritis, endometrial defects, and insufficient blood supply. To obtain sufficient nutrients, the placenta compensatorily expands in area and extends to the lower segment of the uterus.
② Delayed development of the fertilized egg. When it reaches the uterine cavity, the trophoblast has not yet developed to the stage capable of implantation, and it continues to migrate downward into the lower segment of the uterus.
③ Excessive placental area. In cases of multiple gestations, the placenta often extends to the lower segment of the uterus, leading to placenta previa.
### II. Classification
Based on the relationship between the placental margin and the cervical os, placenta previa is classified into three types:
⑴ Complete placenta previa (or central placenta previa), where the entire internal cervical os is covered by placental tissue.
⑵ Partial placenta previa, where part of the internal cervical os is covered by placental tissue.
⑶ Marginal placenta previa, where the placenta is attached to the lower segment of the uterus, with its margin close to but not extending beyond the cervical os.
The relationship between the placental margin and the cervical os may change as the cervical canal disappears and the cervical os gradually dilates. In principle, the relationship at the time of admission is used as the standard for diagnosing the type of placenta previa, which facilitates the formulation of a treatment plan.
### III. Prevention
Promoting contraception and family planning, preventing multiple births, and avoiding multiple curettage procedures or intrauterine infections can help prevent endometrial damage or endometritis. Strengthening prenatal examinations and education is essential. Any bleeding during pregnancy, regardless of the amount, should be treated promptly to achieve early diagnosis and proper management.
### IV. Management
The principle of managing placenta previa is to control bleeding, correct anemia, prevent infection, and select the appropriate time and method for delivery. The priority is the safety of the mother, and under this condition, efforts should be made to avoid premature birth to reduce mortality.
#### (a) Expectant Management
If the pregnancy is less than 36 weeks, the fetal weight is less than 2500g, vaginal bleeding is minimal, the mother is in good general condition, and the fetus is viable, expectant management can be adopted.
1. Absolute bed rest, with sedatives such as phenobarbital 0.03, chlordiazepoxide 10mg, or diazepam 5mg, taken orally three times daily.
2. Inhibition of uterine contractions with salbutamol 2.4-4.8mg, every 4-6 hours, followed by a maintenance dose after contractions cease.
3. Correction of anemia with ferrous sulfate 0.3, taken orally three times daily, with blood transfusions if necessary.
4. Antibiotics to prevent infection.
5. Dexamethasone 10mg, administered intramuscularly or intravenously once daily for three consecutive days to promote fetal lung maturity.
6. Close monitoring of the condition, along with relevant auxiliary examinations such as ultrasound and fetal maturity assessments. If there is heavy or recurrent bleeding, or if labor begins, delivery should be terminated as appropriate.