Hospitals in the Gulf Region aiming to become regional centers of excellence are placing greater emphasis on maternal care. Maternal care is a major indicator of quality – not only of individual hospitals but health care systems on the whole. So it is incumbent on them to learn about best practices in obstetrics, including treating complications that threaten the health of both mother and child.
Placenta praevia is one such condition of pregnancy. In cases of placenta praevia, the placenta covers part or all of the cervix, potentially blocking a baby’s passage into the birth canal. It is one of the leading causes of vaginal bleeding in the second and third trimesters of pregnancy and can potentially endanger the lives of both the mother and infant.
The primary interventions in preventing morbidity and mortality from excessive blood loss include restoring the mother’s hemodynamic stability and delaying delivery or performing a cesaerian section. A gynecologist should be consulted whenever possible.
Placenta praevia is more common than many people think. In general, it affects 1 in 250 women beyond 20 weeks of gestation. But the incidence increases with each pregnancy. The incidence of placenta previa has been reported to be as high as 5% in grand multiparas. The incidence is also increased in women pregnant with multiple gestations (3.9/1000 for twin gestation compared to 2.8/1000 for singleton gestation), says Henry Roqué, MD, MS, of the Division of Maternal-Fetal Medicine at Beth Israel Deaconess Medical Center in Boston, Mass.
Small studies have suggested that the condition may also be more common after the use of assisted fertility techniques. A Norwegian study of over 845,000 pregnancies found nearly a three-fold higher risk of placenta praevia among women who had undergone in vitro fertilization (IVF).
There is no way to prevent placenta praevia, and its causes are unclear. But often it is brought on by previous uterine insult or injury, such as uterine surgery (including a previous C-section delivery, a dilation and curettage (D&C), or an abortion. A scarred endometrium, large placenta, abnormal uterus, or abnormal formation of the placenta can also raise the likelihood of placenta praevia. And it is more common among women who smoke, use cocaine and increases with maternal age (nuliiparous women 40 or older have an incidence of placenta previa of 0.25% compared to nulliparous women age 20-29 yrs).
In addition, placenta praevia occurs far more frequently in women having their second or later babies than in first pregnancies and women who are pregnant with two or more babies. Women who’ve had a placenta praevia in a previous pregnancy have a 4 to 8 percent chance of a recurrence. In this In Practice article, we look at the interventions, outcomes, and complications of placenta praevia.
What are the symptoms of placenta praevia?
Placenta praevia varies in severity, depending on how much of the cervix is covered. Total placenta praevia occurs when the internal cervical os — the small opening of the cervix that dilates during the first stage of labor — is completely covered; partial placenta praevia occurs when the internal os is partially covered; marginal placenta praevia occurs when the placenta is at the margin of the internal os; and low-lying placenta previa occurs when the placenta is implanted in the lower uterine segment. In this variation, the edge of the placenta is near the internal os but does not reach it.
The primary symptom is painless bleeding from the vagina. The bleeding can range from light spotting to very heavy flow. The incidence of placenta previa decreases with increasing gestational age. Therefore when placenta previa is noted in the 3rd trimester it typically will persist to delivery.
The classic presentation of placenta previa is one of painless vaginal bleeding during pregnancy. Symptoms usually come on suddenly. Uterine cramping may occur with the onset of bleeding. For some women, bleeding does not occur until after labor starts, or it may precede labor by several days.
Severe bleeding, or bleeding that lasts more than 24 hours late in pregnancy should be considered a medical emergency.
Diagnosing placenta praevia
In the past, physicians diagnosed placenta praevia by digitally palpating the placental tissue through the cervical canal. But as a small amount of manipulation can substantially raise the risk of hemorrhage.
Today, transabdominal sonography is the test of choice to pinpoint the position of the placenta. When the internal cervical os cannot be visualized or when the results are inconclusive transperineal or transvaginal sonography may be used to confirm the diagnosis of placenta praevia.
Neither of these tests has been show to increase the risk of hemorrhage. In fact, recent studies have shown that transvaginal ultrasound is safer and more accurate than the transabdominal method.
If the location of the placenta is unknown and sonography is not available, a double set-up bimanual examination under anesthesia (EUA) may be performed in the operating room.
How is placenta praevia treated?
Treatment depends on a number of factors:
• the amount of bleeding
• the stage of fetal development (whether the fetus can survive outside the uterus)
• the amount of placenta over the cervix
If a woman presents to the Emergency Department with profuse vaginal bleeding in late pregnancy, immediate priorities are obtaining a gynecologic consultation and maintaining the mother’s hemodynamic stability.
“The cure for hemorrhage secondary to placenta previa is delivery by cesarean section. Therefore the risk to the premature fetus to be delivered must be weighed against the maternal benefit of delivery in cases of significant hemorrhage,” says Roqué. He adds that for patients who are significantly preterm and hemodynamically stable, you may consider expectant management once there has been cessation of the hemorrhage.
For similar patients who are at a gestational age that can be resuscitated by the pediatricians at your hospital you may consider moving to a controlled elective cesarean. In cases where your hospital is not prepared to care for a significantly premature neonate you should consider transport of the stabilized mother/fetus dyad to a facility that could maximally resusitate the neonate.
What are the complications of placenta praevia?
Maternal complications include major hemorrhage, shock, and death. The risk of infection or blood clots also increases, as does the likelihood of the need for a blood transfusion.
Premature delivery (before 36 weeks) is responsible for about 60 percent of infant deaths in cases of placenta praevia. Placental abruption may cause fetal blood loss or hemorrhage, as may surgical entry into the uterus during a C-section delivery.
The maternal mortality rate secondary to placenta praevia <1%. Most maternal deaths are related to uterine bleeding and the complication of disseminated intravascular coagulopathy, a clotting disorder. Babies born to women with placenta praevia tend to weigh less and are at higher risk of neonatal death than babies born to women without placenta praevia.
The good news is that if placenta praevia is managed appropriately through prompt and accurate diagnosis, good prenatal care and close monitoring, giving the mother the proper advice, and then making good judgments about when to apply the appropriate interventions, the probable outcome is excellent.
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