Multiple Birth OffspringPregnancy, MultipleTwinsDiseases in TwinsPregnancyAbortion, HabitualTwins, MonozygoticAbortion, SpontaneousTwins, ConjoinedTwins, DizygoticAbortion, ThreatenedTwin Studies as TopicAbortion, IncompletePregnancy Trimester, FirstPregnancy OutcomePregnancy, TwinAbortion, MissedDilatation and CurettageGestational SacLive BirthPregnancy ComplicationsHistocompatibility, Maternal-FetalMaternal AgeFetal DeathInfertility, FemaleGestational AgeAbortion, InducedCrown-Rump LengthPregnancy RateFertilization in VitroReceptors, Interleukin-8Chorionic VilliStillbirthUltrasonography, PrenatalUterine HemorrhageReproductive Techniques, AssistedPregnancy Reduction, MultifetalKaryotypingTripletsAbortifacient Agents, NonsteroidalEmbryo TransferCongenital AbnormalitiesEmbryo ImplantationBirth RateInfant, NewbornAntibodies, Antiphospholipid