title: Delayed-interval delivery can save the second twin: evidence from a systematic review.
abstract: BACKGROUND
  In case of preterm birth in twins, it is not well established if the second twin benefits from a delayed-interval delivery.
  
  
  OBJECTIVE
  The main objective of this systematic review is to evaluate survival benefit of the second twin from delayed interval delivery compared to the first twin. Secondly, we will evaluate the survival benefit of the procedure when performed equal to or after 24 weeks gestational age of the first born.
  
  
  METHODS
  Delayed interval delivery was defined as every attempt to perform a delayed interval delivery with at minimum placement of a high ligature of the umbilical cord and a delay of delivery of at least 24 hours. Based on the PRISMA method, a systematic review was performed. Controlled and observational studies reporting at least 3 cases of delayed interval delivery in dichorionic diamniotic twin pregnancy describing the outcome of the first and the second twin were included. Case reports and papers on triplet or higher order pregnancies were excluded. Primary data included gestational age and outcome of the first and second born. Metadata concern management strategies (tocolysis, antibiotics, cerclage), neonatal data (sex, birth weight and morbidity) and maternal complications. The methodological quality of included studies was assessed using the "IHE quality appraisal checklist for assessing the quality of case series". Meta-analysis was performed by computing relative risk (RR) with its 95% confidence interval (CI) using the random-effects model. Statistical heterogeneity was tested using theI2and Chi2statistics. Since there is no control group for the secondary outcomes, these are presented by narrative synthesis.
  
  
  RESULTS
  Mortality data were extracted from 13 articles, reporting a total of 128 cases of delayed interval delivery. In the analysis, the second born had a significantly lower mortality risk compared to the first born (relative risk = 0.44, 95% confidence interval = 0.34 - 0.57, P<0.0001, I2= 0%, P=0.70). For the analysis of mortality of the second born foetus versus the first born when the first delivery was at ≥24 weeks of gestational age, 12 articles were included. In the analysis 4 reports were excluded since there were no events (no mortality) in both groups (first and second born) making analysis impossible. For the 36 cases included, the second born had a significantly lower mortality risk compared to the first born if delivery of the first born occurred at ≥ 24 weeks gestational age (relative risk=0.37, 95% confidence interval= 0.17 - 0.82, P=0.014, I2=0%, P=0.82).
  
  
  CONCLUSIONS
  In carefully selected twin pregnancies the survival of the second born twin may improve with delayed interval delivery, also if the first was born at or after 24 weeks. Management protocols in the studies included vary, making it difficult to propose a uniform strategy for delayed interval delivery. Families must be informed about the possibility that a nonviable infant would survive to a periviable gestational age with a risk of severe sequels after birth as well as the possibility of maternal complications.
authors.affiliation: Department of Obstetrics and Gynaecology, Antwerp University Hospital (UZA), Edegem, Belgium.
authors.forename: S
authors.initials: S
authors.lastname: Feys
authors.affiliation: Department of Obstetrics and Gynaecology, Antwerp University Hospital (UZA), Edegem, Belgium.
authors.forename: Y
authors.initials: Y
authors.lastname: Jacquemyn
keywords: Twin; antibiotics; cerclage; delivery; dichorionic; tocolysis