Is it true that placenta previa per se is not a risk factor for perinatal mortality?

Abstract

I read with great interest the article ‘‘Critical analysis of risk factors and outcome of placenta previa’’ by Rosenberg et al. [1], in which two observations were made. First, infertility treatments, prior cesarean section (CS), and advanced maternal age were major risk factors for placenta previa. I agree with these findings. Second, although placenta previa increased the perinatal mortality rate by 5.6 times, placenta previa per se was not the culprit, instead, its associated conditions (preterm birth, growth restriction, and congenital malformation) were the culprits. However, I disagree with the conclusion since it means that placenta previa, in the absence of these conditions, is not a risk factor for perinatal mortality. In other words, placenta previa does not present a risk factor for a term non-malformed normally grown infant. This differs from my clinical impression based on my three decades of experience in obstetrical practice. In my opinion, CS for placenta previa poses three risks to neonates; a view that I believe is shared by many experienced obstetricians. First, CS sometimes induces fetal hemorrhage, leading to neonatal anemia and circulatory collapse. Incision or destruction of the placenta, either accidentally or intentionally, induces hemorrhage, not only maternal but also fetal. Second, ‘‘abdominal dystocia’’ sometimes occurs in CS for placenta previa. The placenta, sometimes being present just adjacent to the incision site and thus bulging, narrows the ‘‘exit’’, preventing a smooth head delivery. Third, resuscitation of the infant, if required, may not be sufficiently provided in a case with unexpectedly severe hemorrhage in an emergent CS setting. General anesthesia may be more frequently employed in CS for placenta previa, especially in an emergent CS. Infant resuscitation may be more frequently required in placenta previa due to the higher possibility of fetal anemia, abdominal dystocia and general anesthesia. CS procedures have been developed to overcome, or at least lessen, the former two problems. First, we perform ultrasound after laparotomy, confirm the placental site and choose the incision site to avoid a transplacental approach as much as possible. If hysterectomy has been decided preoperatively, vertical uterine body incision or transverse uterine fundus incision is employed, which prevents placental incision and thus decreases the amount of hemorrhage [2]. Second, we usually use ‘‘forceps with vacuum’’ to deliver the head, better facilitating delivery than ‘‘manual delivery aided by fundal pressure’’ (Fig. 1). The third problem may be difficult to overcome since it depends on the institutional staffing pattern. Emergent CS at night, when medical staff is limited, may well illustrate the situation. Usually, when an infant is born with asphyxia or circulatory collapse, not only neonatologists but also other staffs on duty, including anesthesiologists or obstetricians, may help resuscitate the infant. However, more medial attention may be required for massive hemorrhage with less attention paid to the infant. Experienced obstetricians may not always be present at emergent CS. Inexperienced and limited staff in emergent CS settings may prevent physicians from performing the procedures described above or cooperating with the infant’s resuscitation. Thus, emergent CS for placenta previa may pose great risks of perinatal mortality. Data from Ananth et al. [3] were in line with this view. Term babies from women with previa, compared with those from women without previa, had a higher neonatal mortality rate, with the mortality rate S. Matsubara (&) Department of Obstetrics and Gynecology and Perinatal Education Center, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi 329-0498, Japan e-mail: matsushi@jichi.ac.jp