All singleton pregnancy cases who 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 details were indicated as follows. 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 done. In cases with a placenta in the anterior uterine wall, surgeons avoided the placenta and, incision was guided by ultrasound . After delivery and until 24 h after 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: surgeon did not remove the placenta by hand and waited until the placenta separated from uterine wall spontaneously; after, placenta was gently removed by hand when part of 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 no sign of placenta separation was completely developed, placenta was not removed and surgeons closed uterine wall and skin incision, performing instead prophylactic uterine artery embolization (UAE) before the development of massive PPH. All 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 prearranged date of cesarean section, an emergency cesarean section was performed. Antenatal bleeding was defined as painless genital bleeding 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. PPH was defined as the amount of bleeding from the end of the cesarean section procedure until 24 h after surgery and, PPH as a blood loss over 500 ml within 24 hours after birth . All included cases were categorized into two groups: Group with PPH (Group A) and Group without PPH (Group B). Cases that underwent allogenic blood transfusion included patients who received blood transfusion at pre-parturition, intraoperation, and postpartum time. Placental adhesion was defined by the surgeon’s clinical judgement when attempting to remove the placenta, after appearance of the placenta peeling sign, but the placenta did not separate smoothly.
We classified placenta previa into two categories according to Calì et al . If the placenta edge covered internal os, it was diagnosed as major type. If, instead, the placenta edge did not cover 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 findings such as uterine bulging, heterogeneous placenta, adjacent organ invasion, and cervical varicosities [16-18].
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-value < 0.05.
This retrospective study was approved by the Institutional Review Board of the National Defense Medical College, Tokorozawa, Japan.