Background:To determine the effects of previous placenta previa on the maternal and neonatal outcomes of the next pregnancy. Methods: This 10-year retrospective cohort study was conducted in the Department of Obstetrics and Gynecology, Third Affiliated Hospital of Guangzhou Medical University, between January 2009 and 2018. We retrospectively analyzed the effects of a previous singleton pregnancy in women with and without placenta previa on the outcomes of the subsequent pregnancy. To control for confounders, we used multiple logistic regression models. Results: A total of 57,251 women with singleton pregnancies gave birth during the 10-year study period. Among them, 6070 women had two consecutive births. For the first pregnancy, 1603 women delivered by cesarean delivery and 4467 by vaginal delivery. Among women with a history of cesarean delivery, placenta previa was an independent risk factor for hemorrhage (adjusted odds ratio [aOR]: 2.25, 95% confidence interval [CI]: 1.1-4.62), placenta accreta spectrum (PAS) disorders (aOR: 4.11, 95% CI: 1.68-10.06), and placenta previa (aOR: 6.24, 95% CI: 2.85-13.67) during the subsequent pregnancy. Puerperal infection, blood transfusion, and perinatal outcomes did not significantly differ between women with a history of placenta previa and women without this history. Among women with a history of vaginal delivery, placenta previa increased the risk of PAS disorders (aOR: 5.71, 95% CI: 1.81-18.03) and placenta previa (aOR: 4.14, 95% CI: 1.07-16.04) during the subsequent pregnancy. There was no significant difference between the two groups in terms of hemorrhage, blood transfusion, puerperal infection, and perinatal outcomes. Conclusions: Women with a history of placenta previa are at risk for adverse outcomes such as postpartum hemorrhage, PAS disorders, and placenta previa in the subsequent pregnancy.

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We study a multiclass open-queueing network with a set of single-server stations that operate under a combination of FIFO (first-in-first out) and priority service disciplines, and are subject to random breakdowns. Assuming that the primitive processes—in particular, external arrivals, service requirements, service capacities (up and down times), and the routing mechanism—follow two-moment approximations (based on functional central limit theorems), we develop a semi-martingale reflected Brownian motion (SRBM) approximation for the performance processes such as workload, queue lengths, and sojourn times. We illustrate through numerical examples in comparison against simulation that the SRBM approximation, while not always supported by a limit theorem, exhibits good accuracy in most cases. Through analyzing special networks, we also discuss the existence of the SRBM approximation in relation to the stability and the heavy traffic limits of the networks.

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