Department of Health Services Research and Policy, London School of Hygiene and Tropical Medicine, London WC1H 9SH, UK.
Hum Reprod. 2013 Jul;28(7):1943-52. doi: 10.1093/humrep/det130. Epub 2013 May 3.
Is there an association between a Caesarean section and subsequent fertility?
Most studies report that fertility is reduced after Caesarean section compared with vaginal delivery. However, studies with a more robust design show smaller effects and it is uncertain whether the association is causal.
A previous systematic review published in 1996 summarizing six studies including 85 728 women suggested that Caesarean section reduces subsequent fertility. The included studies suffer from severe methodological limitations.
STUDY DESIGN, SIZE, DURATION: Systematic review and meta-analysis of cohort studies comparing subsequent reproductive outcomes of women who had a Caesarean section with those who delivered vaginally.
PARTICIPANTS/MATERIALS, SETTING, METHODS: Searches of Cochrane Library, Medline, Embase, CINAHL Plus and Maternity and Infant Care databases were conducted in December 2011 to identify randomized and non-randomized studies that compared the subsequent fertility outcomes after a Caesarean section and after a vaginal delivery. Eighteen cohort studies including 591 850 women matched the inclusion criteria. Risk of bias was assessed by the Newcastle-Ottawa scale (NOS). Data extraction was done independently by two reviewers. The meta-analysis was based on a random-effects model. Subgroup analyses were performed to assess whether the estimated effect was influenced by parity, risk adjustment, maternal choice, cohort period, and study quality and size.
The impact of Caesarean section on subsequent pregnancies could be analysed in 10 studies and on subsequent births in 16 studies. A meta-analysis suggests that patients who had undergone a Caesarean section had a 9% lower subsequent pregnancy rate [risk ratio (RR) 0.91, 95% confidence interval (CI) (0.87, 0.95)] and 11% lower birth rate [RR 0.89, 95% CI (0.87, 0.92)], compared with patients who had delivered vaginally. Studies that controlled for maternal age or specifically analysed primary elective Caesarean section for breech delivery, and those that were least prone to bias according to the NOS reported smaller effects.
LIMITATIONS, REASONS FOR CAUTION: There is significant variation in the design and methods of included studies. Residual bias in the adjusted results is likely as no study was able to control for a number of important maternal characteristics, such as a history of infertility or maternal obesity.
Further research is needed to reduce the impact of selection bias by indication through creating more comparable patient groups and applying risk adjustment.
剖宫产是否会影响随后的生育能力？
大多数研究报告显示，与阴道分娩相比，剖宫产会降低生育能力。然而，设计更为严谨的研究显示影响较小，并且尚不确定这种关联是否具有因果关系。
1996 年发表的一项系统评价总结了 6 项研究，共纳入 85728 名女性，表明剖宫产会降低随后的生育能力。纳入的研究存在严重的方法学局限性。
研究设计、大小和持续时间：系统评价和荟萃分析比较了剖宫产妇女与阴道分娩妇女随后的生殖结局的队列研究。
参与者/材料、设置、方法：2011 年 12 月，对 Cochrane 图书馆、Medline、Embase、CINAHL Plus 和母婴护理数据库进行了检索，以确定比较剖宫产和阴道分娩后随后生育结局的随机和非随机研究。有 18 项队列研究符合纳入标准，共纳入 591850 名女性。使用纽卡斯尔-渥太华量表（NOS）评估偏倚风险。数据提取由两名独立评审员完成。荟萃分析基于随机效应模型。进行了亚组分析，以评估估计的效果是否受产次、风险调整、产妇选择、队列期以及研究质量和大小的影响。
有 10 项研究可以分析剖宫产对随后妊娠的影响，16 项研究可以分析剖宫产对随后分娩的影响。荟萃分析表明，与阴道分娩的患者相比，行剖宫产的患者随后妊娠率降低 9%[风险比（RR）0.91，95%置信区间（CI）（0.87，0.95）]，出生率降低 11%[RR 0.89，95% CI（0.87，0.92）]。根据 NOS 报告，控制产妇年龄或专门分析臀位分娩的初次选择性剖宫产、以及受偏倚影响最小的研究报告的影响较小。
纳入研究的设计和方法存在很大差异。调整结果中仍存在显著偏差，因为没有研究能够控制许多重要的产妇特征，如不孕史或肥胖。
需要进一步研究通过创建更具可比性的患者群体和应用风险调整来减少指征选择偏倚的影响。
