From the Guidelines
Placenta previa is a pregnancy complication where the placenta attaches too low in the uterus, partially or completely covering the cervix, posing significant risks to both maternal and fetal health through uncontrolled vaginal bleeding. This condition is diagnosed in the third trimester when the placenta overlies the internal cervical os, and it is common in the first half of pregnancy, but often resolves by 28 weeks 1. However, 0.4% of all pregnancies are diagnosed with placenta previa in the third trimester, which can lead to spontaneous labor and requires careful management.
Key Characteristics of Placenta Previa
- Placenta previa is classified into three types: complete, partial, and marginal, depending on the extent of cervical coverage.
- Risk factors for placenta previa include previous cesarean deliveries, prior uterine surgeries, multiple pregnancies, advanced maternal age, and smoking 1.
- The incidence of placenta previa increases with the number of previous cesarean deliveries, occurring in 9,17, and 30 per 1,000 women with one, two, and three or more cesarean deliveries, respectively 1.
Management and Recommendations
- Women diagnosed with placenta previa after 28 weeks' gestation should avoid moderate-to-vigorous physical activity (MVPA) to minimize the risk of spontaneous labor and vaginal bleeding 1.
- However, these women should maintain their activities of daily living and low-intensity activity, such as walking, to promote overall health and well-being 1.
- Management typically involves pelvic rest, monitoring, and planned cesarean delivery, usually around 36-37 weeks of pregnancy, to ensure the best possible outcomes for both mother and baby.
From the Research
Definition of Placenta Previa
- Placenta previa (PP) is characterized by abnormal placental placement in the lower uterine segment, obstructing the cervical opening 2.
- It can lead to placenta accreta spectrum (PAS), where the placenta adheres abnormally to the uterine wall, complicating separation 2.
Types of Placenta Previa
- Placenta previa totalis (PPT) occurs when the placenta completely covers the internal cervical os 2.
- Partial previa is used to describe cases where the placenta partially covers the os, but this term may be restricted to cases with cervical dilatation 3.
- Low-lying placenta is preferred when the placenta implants in the lower uterine segment but does not reach the cervix 3.
Risk Factors and Diagnosis
- Risk factors for placenta previa include prior cesarean delivery, pregnancy termination, intrauterine surgery, smoking, multifetal gestation, increasing parity, and maternal age 4.
- The diagnostic modality of choice for placenta previa is transvaginal ultrasonography 4.
- The location of the placenta should always be examined with ultrasonography to allow better preoperative planning 5.
Management and Complications
- Women with a complete placenta previa should be delivered by cesarean 4.
- Small studies suggest that, when the placenta to cervical os distance is greater than 2 cm, women may safely have a vaginal delivery 4, 3.
- Placenta accreta spectrum (PAS) poses significant maternal risks, necessitating early diagnosis and meticulous surgical planning 2.
- Hysterectomy remains a critical intervention in cases of uncontrollable bleeding, with postoperative care focused on hemodynamic stabilization and pain management 2.