All singleton pregnancy cases that underwent cesarean section due to placenta previa at our institution, between January 2003 and February 2015, were identified. The inclusion and exclusion criteria were decided according to surgical procedures. The basic surgical procedure for placenta previa was performed as previously described by Soyama et al. . Briefly, after abdominal wall incision, a transverse incision into the lower segment of the uterus was performed. In cases with a placenta in the anterior uterine wall, surgeons avoided the placenta and the incision was guided by ultrasound . After delivery and until 24 h after the cesarean section, oxytocin 5 IU was started intravenously in a 500-mL saline drip. Methods to remove the placenta and to treat postoperative hemorrhage were as follows: the surgeon did not remove the placenta by hand and waited until the placenta separated from the uterine wall spontaneously; afterwards, the placenta was gently removed by hand when part of the placenta was exfoliated and another part was retained in the uterine wall. If intraoperative hemorrhage developed, gauze packing or brace sutures, such as placental bed sutures or compression sutures, alone or combined, were performed at the surgeon’s discretion. Cases that did not receive any hemostatic procedures, as mentioned above, were included in our study. Hence, when the placenta did not separate, surgeons did not remove the placenta, closed the uterine wall and skin incision, and performed prophylactic uterine artery embolization (UAE). These cases were excluded from this study.
Maternal history and intraoperative information were obtained from medical charts and operative records. In all cases, US and MRI examinations for the diagnosis of placenta previa were performed by experienced obstetricians and radiologists after 30 weeks of gestation. At our institution, elective cesarean section was performed before 38 weeks of gestation according to the Guidelines for Obstetrical Practice in Japan . However, if persistent antenatal bleeding over 100 ml or uncontrollable uterine contractions occurred before the prearranged date of cesarean section, an emergency cesarean section was performed. Antenatal bleeding was defined as painless genital bleeding stemming from the placenta. The amount of intraoperative hemorrhage was measured from the time of the skin incision to the time of scar closure, based on suction count and towel weight. Massive postoperative hemorrhage was defined as the amount of bleeding from the end of the cesarean section procedure until 24 h after surgery and a blood loss over 500 ml within 24 hours after birth .Lochia, which attached to maternity pads to measure postoperative hemorrhage was assessed. All included cases were categorized into two groups: Group A, massive postoperative hemorrhage and Group B, all cases without massive postoperative hemorrhage. Cases that underwent allogenic blood transfusion included patients who received blood transfusion at pre-parturition, intraoperation, and postpartum time. Placental adhesion was defined as no natural removal of the placenta after 2 minutes from the time of delivery.
We classified placenta previa into two categories according to Calì et al. . If the placental edge covered the internal os, it was diagnosed as major type. If the placental edge did not cover the cervical internal os and was located in the lower uterine segment, it was classified as minor type.
Antenatal diagnosis of adherent placenta was assessed by MRI for uterine bulging, heterogeneous placenta, adjacent organ invasion, and cervical varicosities [16-18]. The pathological diagnosis of placenta accreta spectrum was performed using the placenta. We routinely used uterotonic drugs for all cases after performing cesarean section. When massive postoperative hemorrhage developed, the amount of uterotonic drugs was increased. If postoperative hemorrhage was uncontrollable, intrauterine balloon tamponade was performed. If all interventions failed, uterine artery embolization was performed.
Statistical analysis was performed using JMP Pro 14 software (SAS Institute Inc., Cary, NS, USA). Chi-squared test, Fisher's exact test, and Mann-Whitney U test were used to evaluate the clinical significance of clinical factors. Statistical significance was defined as a p < 0.05.
This retrospective study was approved by the Institutional Review Board of the National Defense Medical College, Tokorozawa, Japan.