Labor Onset, Oxytocin Use, and Epidural Anesthesia for Vaginal Birth after Cesarean Section and Associated Effects on Maternal and Neonatal Outcomes in a Tertiary Hospital in China： A Retrospective Study

Background：In the mainland of China, the trial of labor after cesarean section is still a relatively new technique. In this study, we aimed to investigate the effects of labor onset, oxytocin use, and epidural anesthesia on maternal and neonatal outcomes for vaginal birth after cesarean section （VBAC） in a tertiary hospital in China.Methods：This was a retrospective study carried out on 212 VBAC cases between January 2015 and June 2017 in Beijing Obstetrics and Gynecology Hospital, Capital Medical University. Relevant data were acquired on a form, including maternal age, gravidity and parity, body mass index before pregnancy, weight gain during pregnancy, type of labor onset, gestational age, the use of oxytocin and epidural anesthesia, birth mode, the duration of labor, and neonatal weight. The factors affecting maternal and neonatal outcomes for cases involving VBAC, especially with regards to postpartum hemorrhage （PPH） and fetal distress, were evaluated by univariate analysis and multivariable logistic regression.Results：Data showed that 36 women （17.0%） had postpartum hemorrhage （PPH） and 51 cases （24.1%） featured fetal distress. Normal delivery took place for 163 infants （76.9%） while 49 infants （23.1%） underwent operative vaginal deliveries with forceps. There were 178 cases （84.0%） of spontaneous labor and 34 cases （16.0%） required induction. Oxytocin was used in 54 cases （25.5%） to strengthen uterine contraction, and 65 cases （30.7%） received epidural anesthesia. The rate of normal delivery in cases involving PPH was significantly lower than those without PPH （61.1% vs. 80.1%; χ2 = 6.07, P = 0.01）. Multivariate logistic analysis showed that the intrapartum administration of oxytocin （odds ratio [OR] = 2.47; 95% confidence interval [CI] = 1.07–5.74; P = 0.04） and birth mode （OR = 0.40; 95% CI = 0.18–0.87; P = 0.02） was significantly associated with PPH in VBAC cases. Operative vaginal delivery occurred more frequently in the group with fetal distress than the group without （49.0% vs. 14.9%, χ2 = 25.36, P = 0.00）. Multivariate logistic analysis also revealed that the duration of total labor （OR = 1.01; 95% CI = 1.00–1.03; P = 0.04） and the gestational week of delivery （OR = 1.08; 95% CI = 1.05–1.11; P = 0.00） were significantly associated with fetal distress in VBAC.Conclusions：The administration of oxytocin during labor and birth was identified as a protective factor for PPH in VBAC while birth mode was identified as a risk factor. Finally, the duration of total labor and the gestational week of delivery were identified as risk factors for fetal distress in cases of VBAC. This information might help obstetricians provide appropriate interventions during labor and birth for VBAC.

Chromium enrichment in different crystalline phases of Cr-containing slag under various basicities and equilibrium temperatures

The effects of basicities and equilibrium temperatures on the enrichment of chromium in different mineral phases of synthesized argon-oxygen decarburization slags were investigated to understand the Cr concentrating behavior into Mg(Cr,Al)2O4 spinel phase and to determine the leaching stability of Cr-containing slag.The results showed that when the basicity decreased from 1.0 to 0.6 and temperatures decreased from 1600 to 800℃,the Cr content of amorphous phase and crystalline phase gradually decreased,with a subsequent increase in the Cr content of spinel phase.The range of Cr enrichment in spinel of slags S1,S2,and S3 is 92.03-96.89,91.63-96.36,and 90.67-95.42,respectively.The mass fraction and the size of spinel increased with the decreasing equilibrium temperatures,and the Cr leaching values decreased simultaneously.Therefore,the trend of the amount of Cr-related ions in the leachate was consistent with the trend of Cr in the amorphous phase,diopside,and akermanite.The results suggest that the lower basicity and equilibrium temperatures could be conducive to stabilizing Cr into spinel phase to minimize Cr leaching into the environment.