Objective

Current data on the role of the umbilical cord in pregnancy complications are conflicting; estimates of the proportion of stillbirths due to cord problems range from 3.4 to 26.7%. A systematic review and meta-analysis were undertaken to determine which umbilical cord abnormalities are associated with stillbirth and related adverse pregnancy outcomes.

Methods

MEDLINE, EMBASE, CINAHL and Google Scholar were searched from 1960 to present day. Reference lists of included studies and grey literature were also searched. Cohort, cross-sectional, or case-control studies of singleton pregnancies after 20 weeks’ gestation that reported the frequency of umbilical cord characteristics or cord abnormalities and their relationship to stillbirth or other adverse outcomes were included. Quality of included studies was assessed using NIH quality assessment tools. Analyses were performed in STATA.

Results

This review included 145 studies. Nuchal cords were present in 22% of births (95% CI 19, 25); multiple loops of cord were present in 4% (95% CI 3, 5) and true knots of the cord in 1% (95% CI 0, 1) of births. There was no evidence for an association between stillbirth and any nuchal cord (OR 1.11, 95% CI 0.62, 1.98). Comparing multiple loops of nuchal cord to single loops or no loop gave an OR of 2.36 (95% CI 0.99, 5.62). We were not able to look at the effect of tight or loose nuchal loops. The likelihood of stillbirth was significantly higher with a true cord knot (OR 4.65, 95% CI 2.09, 10.37).

Conclusions

True umbilical cord knots are associated with increased risk of stillbirth; the incidence of stillbirth is higher with multiple nuchal loops compared to single nuchal cords. No studies reported the combined effects of multiple umbilical cord abnormalities. Our analyses suggest specific avenues for future research.

中文翻译：

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脐带特征及其与不良妊娠结局的关系：系统评价和荟萃分析

目的

有关脐带在妊娠并发症中作用的最新数据相互矛盾。因脐带问题而死产的比例估计在3.4至26.7％之间。进行了系统的审查和荟萃分析，以确定哪些脐带异常与死产和相关的不良妊娠结局有关。

方法

从1960年至今搜索MEDLINE，EMBASE，CINAHL和Google Scholar。还检索了纳入研究和灰色文献的参考文献清单。包括对妊娠20周后单胎妊娠的队列研究，横断面研究或病例对照研究，这些研究报告了脐带特征或脐带异常的频率及其与死产或其他不良后果的关系。使用NIH质量评估工具评估纳入研究的质量。分析在STATA中进行。

结果

该评价包括145项研究。新生儿中有22％的人有脐带（95％CI 19，25）；4％（95％CI 3，5）出现脐带多环，而1％（95％CI 0，1）出生的脐带有真正的结。没有证据表明死产和任何脐带之间存在关联（OR 1.11，95％CI 0.62，1.98）。将颈索的多圈与单圈或无圈进行比较，得出OR为2.36（95％CI 0.99，5.62）。我们无法查看紧绷或松弛的牙龈环的影响。真正的绳结打死的可能性更高（OR 4.65，95％CI 2.09，10.37）。

结论

真正的脐带结会增加死胎的风险；与单个脐带相比，多个脐带loop死胎的发生率更高。没有研究报道多种脐带异常的综合作用。我们的分析为将来的研究提出了具体的途径。