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719: Risk of preterm birth in a singleton pregnancy following prior preterm twin birth: a systematic review and meta-analysis

      Objective

      To conduct a systematic review and meta-analyses of literature regarding the risk of preterm birth in singleton pregnancies following a prior preterm twin birth.

      Study Design

      We conducted a literature search of Embase, Medline, Cochrane and PubMed from inception until July 31, 2017 for studies evaluating women with a prior twin birth followed by a singleton birth. Local retrospective data was also included in the study. Data were abstracted and summary unadjusted odds ratios (uAOR) and confidence intervals (CI) were calculated using fixed effects model. A priori, the protocol was developed and registered with PROSPERO (Registration number: CRD42017053382).

      Results

      Six studies at low risk-of-bias met inclusion criteria. Compared to women with previous term twin births, women who had previous preterm (<37 weeks gestation at birth) twin births were at increased odds of preterm singleton birth in subsequent pregnancy (unadjusted OR 4.76; 95% CI, 3.04-7.47). Gestational age at birth of previous twin pregnancy was an effect modifier. Compared to previous term twin births, the odds of subsequent preterm singleton birth were uAOR 2.16 (95% CI, 1.24 - 3.76) if twins were born between 34 and 366 weeks, uAOR 5.19 (95% CI, 2.83 - 9.51) if twins were born between 30 and 336 weeks and uAOR 9.4 (95% CI, 5.39 - 16.4) if twins were born before 30 weeks gestation (Table 1).

      Conclusion

      History of preterm twin birth is associated with higher odds of subsequent preterm singleton birth. In addition, the odds increase with reducing gestational age of previous twin birth.
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