**8. Antenatal complications**

Certainly, preterm birth is the most relevant complication related to multiple pregnan‐ cies. Current available data in the literature are insufficient to determine effective preven‐ tive strategies, limiting the applicability of routine screening methods to predict preterm delivery [55].

Two recent systematic reviews and meta-analysis concerning the use of transvaginal sono‐ graphic cervical length to predict spontaneous preterm birth in twin pregnancies concluded that women with a short cervix are at increased risk [61, 62]. Testing for fetal fibronectin should not be used as a single approach to suppose a greater risk of preterm delivery in twins. If combined with cervical length measurement it might be valuable [55, 56]. Also, women with a history of previous preterm singleton delivery are at increased risk of preterm birth in a subsequent twin pregnancy [63].

All studied interventions to prevent spontaneous preterm labour in twin pregnancies up to date failed, including hospitalization and bed rest, progesterone treatment, prophylactic cervical cerclage or pessary and the use of betamimetics [64-69]. This is the rationale for worldwide guidelines to discourage any of the above-mentioned strategies [56, 59, 70]. Further well-designed, properly powered, prospective randomized trials are warranted prior to widespread implementation in clinical practice.

It is well known that both antenatal corticosteroids and magnesium sulphate reduce neonatal complications in preterm babies related to lung maturity and neurological development respectively, regardless of fetal number [71, 72]. Although, there is no evidence to support neither the routine use of untargeted course of steroids nor magnesium sulphate therapy, except when preterm labour or birth is imminent [55, 56, 70].

Other antenatal complications, including those specific to monochorionic twins, were exhaus‐ tively discussed along the chapter.
