Risk of singleton preterm birth after prior twin preterm birth: a systematic review and meta-analysis.

OBJECTIVE DATA

The purpose of this study was to conduct a systematic review and meta-analyses of literature regarding the risk of preterm birth in singleton pregnancies after a preterm twin birth.

STUDY

We conducted a literature search of Embase, Ovid Medline, and Cochrane from inception until February 28, 2019. Studies that evaluated women with a previous twin birth followed by a singleton birth were included.

STUDY APPRAISAL AND SYNTHESIS METHODS

Data were abstracted in duplicate, and summary odds ratios and confidence intervals were calculated with the use of random effects model. Risk of bias was assessed with the use of the Newcastle-Ottawa Scale, and quality of evidence was evaluated with the use of the Grades of Recommendation, Assessment, Development, and Evaluation approach. The primary outcome was a preterm singleton birth (<37 weeks gestational age); secondary outcomes included risk of late preterm birth (34-36+6 weeks gestation), preterm birth between 30 and 33+6 weeks gestation, and preterm birth at <30 weeks gestation. Subanalysis of risk of singleton preterm birth after spontaneous twin birth was also performed. A priori, the protocol was developed and registered with PROSPERO (2016; registration number: CRD42017053382).

RESULTS

We included 8 cohort studies at low risk-of-bias met inclusion criteria for the systematic review and 6 for the meta-analysis. Compared with women with previous term twin births, women who had previous preterm (<37 weeks gestation) twin births were at increased odds of preterm singleton birth in subsequent pregnancy (odds ratio, 4.34; 95% confidence interval, 2.83-6.65). Gestational age at birth of previous twin pregnancy was an effect modifier. Compared with previous term twin births, the odd ratios of subsequent preterm singleton birth were 2.13 (95% confidence interval, 1.21-3.74) if twins were born between 34 and 36+6 weeks gestation, 5.18 (95% confidence interval, 2.78-9.64) if twins were born between 30 and 33+6 weeks gestation, and 9.78 (95% confidence interval, 4.99-18.98) if twins were born at <30 weeks gestation. A similar trend was seen for the risk of singleton preterm birth after spontaneous twin preterm birth.

CONCLUSION

A history of preterm twin birth is associated with higher odds of subsequent preterm singleton birth. The odds increase with decreasing gestational age of previous twin birth.