Levine Lisa D, Srinivas Sindhu K
Maternal and Child Health Research Program, Department of Obstetrics and Gynecology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA.
Maternal and Child Health Research Program, Department of Obstetrics and Gynecology, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA.
Am J Obstet Gynecol. 2016 Apr;214(4):535.e1-535.e4. doi: 10.1016/j.ajog.2015.10.919. Epub 2015 Oct 31.
During the second stage of labor, it is plausible that the pressure of the fetal head against a completely dilated cervix may lead to changes in the cervical integrity and cervical strength lending it susceptible to premature dilation in a subsequent pregnancy. Therefore, a prolonged second stage of labor has been hypothesized to be a risk factor for cervical insufficiency and spontaneous preterm birth (sPTB).
We sought to evaluate the effect that the length of second stage of labor in one pregnancy has on the risk of sPTB in a subsequent pregnancy.
This was a planned secondary analysis of a large retrospective cohort study of women with 2 consecutive deliveries at our institution from 2005 through 2010. Women with a term pregnancy that reached the second stage were included; women with a prior sPTB were excluded. The primary outcome was sPTB <37 weeks. A prolonged second stage was defined as ≥3 hours. Fisher exact tests were used to compare categorical data. Linear and logistic regression was used to calculate odds.
In all, 757 women were included. The overall length of the second stage ranged from 0-7.3 hours. The sPTB rate in a subsequent pregnancy was 8.7%. There was no association between length of second stage (hours) as a continuous variable and sPTB after adjusting for confounders (adjusted odds ratio, 0.83; [95% CI 0.58-1.20]). A prolonged second stage ≥3 hours occurred in 48 (6.3%) women. Women with a second stage ≥3 hours were older, less likely to be African American, and were less likely to be overweight or obese as compared to women with a second stage <3 hours. The women with second stage ≥3 hours were more likely to be nulliparous and have a larger neonate. The sPTB risk was not different between a second stage ≥3 hours (10.4%) and <3 hours (7.9%), P = .5. The sPTB risk was, however, modified by mode of delivery in the second stage. There was no difference in sPTB rate among women with a vaginal delivery when comparing those with and without a prolonged second stage (7.4 vs 7.8%, P = .9). There also was no difference among women with a cesarean when comparing those with and without a prolonged second stage (11.8 vs 14.3%, P = .8). While not statistically significant, the absolute risk of a subsequent sPTB after a cesarean delivery with a second stage ≥3 hours is twice as high as the risk of a sPTB after a vaginal delivery with a second stage ≥3 hours (adjusted odds ratio, 2.08; [0.32-13.78]).
A prolonged second stage of labor alone does not increase the risk of sPTB in a subsequent pregnancy. Cesarean delivery after a prolonged second stage of labor may confer a possible increased risk. It is important to continue to evaluate potential risk factors for sPTB. If these risk factors are confirmed in future studies, it will aid in the counseling of women and may open the door for therapeutic strategies to be studied among these newly identified at-risk women.
在第二产程中，胎儿头部对完全扩张的宫颈的压力可能导致宫颈完整性和宫颈强度发生变化，使其在随后的妊娠中易发生宫颈过早扩张，这似乎是合理的。因此，有人推测第二产程延长是宫颈机能不全和自发性早产（sPTB）的一个危险因素。
我们试图评估一次妊娠中第二产程的时长对随后妊娠中sPTB风险的影响。
这是一项对2005年至2010年在我们机构连续分娩两次的女性进行的大型回顾性队列研究的计划二次分析。纳入妊娠足月且进入第二产程的女性；排除既往有sPTB的女性。主要结局是<37周的sPTB。第二产程延长定义为≥3小时。采用Fisher精确检验比较分类数据。使用线性回归和逻辑回归计算比值比。
总共纳入了757名女性。第二产程的总时长为0至7.3小时。随后妊娠中的sPTB发生率为8.7%。在校正混杂因素后，作为连续变量的第二产程时长（小时）与sPTB之间没有关联（校正比值比，0.83；[95%置信区间0.58 - 1.20]）。48名（6.3%）女性出现第二产程≥3小时。与第二产程<3小时的女性相比，第二产程≥3小时的女性年龄更大，非裔美国人的可能性更小，超重或肥胖的可能性更小。第二产程≥3小时的女性更可能为初产妇且新生儿更大。第二产程≥3小时（10.4%）和<3小时（7.9%）时的sPTB风险没有差异，P = 0.5。然而，第二产程中的分娩方式会改变sPTB风险。在阴道分娩的女性中，比较有无第二产程延长的女性，sPTB发生率没有差异（7.4%对7.8%，P = 0.9）。在剖宫产的女性中，比较有无第二产程延长的女性，sPTB发生率也没有差异（11.8%对14.3%，P = 0.8）。虽然无统计学意义，但第二产程≥3小时后剖宫产的后续sPTB绝对风险是第二产程≥3小时后阴道分娩的sPTB风险的两倍（校正比值比，2.08；[0.32 - 13.78]）。
单纯的第二产程延长不会增加随后妊娠中sPTB的风险。第二产程延长后进行剖宫产可能会带来可能增加的风险。继续评估sPTB的潜在危险因素很重要。如果这些危险因素在未来研究中得到证实，将有助于为女性提供咨询，并可能为在这些新确定的高危女性中研究治疗策略打开大门。
