The rate of twin deliveries in 2008 was 15.6 per 1000 in France, an increase of approximately 80% since the beginning of the 1970s. It is recommended that chorionicity be diagnosed as early as possible in twin pregnancies (Professional Consensus). The most relevant signs (close to 100%) are the number of gestational sacs between 7 and 10 weeks and the presence of a lambda sign between 11 and 14 weeks (Professional Consensus). In twin pregnancies, nuchal translucency is the best parameter for evaluating the risk of aneuploidy (Level B). The routine use of serum markers during the first or the second trimester is not recommended (Professional Consensus). In the case of a choice about sampling methods, chorionic villus sampling is recommended over amniocentesis (Professional Consensus). Monthly follow-up by a gynaecologist-obstetrician in an appropriate facility is recommended for dichorionic pregnancies (Professional Consensus). A monthly ultrasound examination including an estimation of fetal weight and umbilical artery Doppler is recommended (Professional Consensus). It is recommended to plan delivery of uncomplicated dichorionic diamniotic twin pregnancies from 38 weeks and before 40 weeks (Level C). Monthly prenatal consultations and twice-monthly ultrasound are recommended for monochorionic twins (Professional Consensus). It is reasonable to consider delivery from 36 weeks but before 38 weeks+6 days, with intensified monitoring during that time (Professional Consensus). Prenatal care of monochorionic pregnancies must be provided by a physician working in close collaboration with a facility experienced in the management of this type of pregnancy and its complications (Professional Consensus). The increased risk of maternal complications and the high rate of medical interventions justify the immediate and permanent availability of a gynaecologist-obstetrician with experience in the vaginal delivery of twins (Professional Consensus). It is recommended that the maternity ward where delivery takes place have rapid access to blood products (Professional Consensus). Only obstetric history (history of preterm delivery) (Level C) and transvaginal ultrasound measurement of cervical length (Level B) are predictive factors for preterm delivery. No study has shown that the identification by transvaginal sonography (TVS) of a group at risk of preterm delivery makes it possible to reduce the frequency of such deliveries in asymptomatic patients carrying twins (Professional Consensus). It is important to recognize signs of TTTS early to improve the management of these pregnancies (Professional Consensus). Treatment and counseling must be performed in a center that can offer fetoscopic laser coagulation of placental anastomoses (Professional Consensus). This laser treatment is the first-line treatment (Level B). In the absence of complications after laser treatment, planned delivery is recommended from 34 weeks and no later than 37 weeks (Professional Consensus). For delivery, it is desirable for women with a twin pregnancy to have epidural analgesia (Professional Consensus). The studies about the question of mode of delivery have methodological limitations and lack of power. Active management of the delivery of the second twin is recommended to reduce the interval between the births of the two twins (Level C). In the case of non-cephalic presentation, total breech extraction, preceded by internal version manoeuvres if the twin's position is transverse, is associated with the lowest cesarean rates for second twins (Level C). In the case of high and not yet engaged cephalic presentation and if the team is appropriately trained, version by internal manoeuvres followed by total breech extraction is to be preferred to a combination of resumption of pushing, oxytocin perfusion, and artificial rupture of the membranes, because the former strategy appears to be associated with fewer cesareans for the second twin (Level C).
