Related Factors For Preterm Birth in Twins After Single Intrauterine Death：a case control study

Abstract Background Single intrauterine death in twin pregnancy has become a relatively frequent complication of twin pregnancy. Preterm delivery is one of the complications with high incidence, and is closely related to the prognosis of the surviving fetus. However, studies about preterm delivery related to single intrauterine death are limited. The purpose of this paper is to analyze the factors associated with preterm birth in twins after single intrauterine death.Methods This was a case-control study of single intrauterine death in twins delivered at Shengjing Hospital over a 12-year period, from January 1, 2008, to November 30, 2020. We classified these cases into the preterm birth group and full-term birth group according to gestational age at birth. We selected age, gestational age at Single intrauterine death, and parity, etc, as related factors of the preterm birth group. Logistic regression analyses were performed to determine the relevance and importance of related factors and their association with preterm birth. We divided the preterm birth group into four smaller groups according to gestational age at single intrauterine death (14-19 weeks, 20-24 weeks, 25-30 weeks, and 31-36 weeks) and compared them. To exclude human intervention, we analyzed the spontaneous delivery cases as well.Results The analysis included 175 twins (mean [SD] gestational age at single intrauterine death, 27.0 [5.8] weeks; mean [SD] gestational age at birth, 33.8 [3.2] weeks ) with single intrauterine death. A total of 139 (79.4%) were cases of preterm birth. A significant risk factor associated with preterm birth was gestational age at single intrauterine death (odds ratio [OR], 2.89; 95% CI, 1.90-4.39). We found that the 14- to 19-week age group had the oldest gestational age at birth (37.25 [1.29]weeks ). The length of gestation in 14-19 weeks group, 20-24 weeks group, 25-30 weeks group and 31-36 weeks group were 20.5 weeks, 11.0 weeks, 4.77 weeks and 1.12 weeks respectivelyConclusion The fetus’ gestational age at single intrauterine death was a risk factor for preterm birth in their twin. The length of gestation was inversely proportional to increasing gestational age at single intrauterine death.