Monochronioric (MC) twin pregnancies are considered as high-risk pregnancies with potential complications requiring in-utero interventions. We aimed to assess prenatal attachment, anxiety, post-traumatic stress disorder (PTSD) and depressive symptoms in MC pregnancies complicated with Twin-To-Twin-transfusion syndrome (TTTS) in comparison to uncomplicated monochorionic (UMC) and dichorionic pregnancies (DC). Auto-questionnaires were filled out at diagnosis of TTTS and at successive milestones. Prenatal attachment, PTSD, anxiety and perinatal depression were evaluated respectively by the Prenatal Attachment Inventory (PAI) completed for each twin, the Post-traumatic Checklist Scale (PCLS), the State-Trait Anxiety Inventory (STAI) and the Edinburgh Perinatal Depression Scale (EPDS). There was no significant difference in the PAI scores between the two twins. In the DC and UMC groups, PAI scores increased throughout pregnancy, whilst it didn’t for TTTS group. TTTS and DC had a similar prenatal attachment while MC mothers expressed a significantly higher attachment to their fetuses and expressed it earlier. At the announcement of TTTS, 72% of the patients present a score over the threshold at the EPDS Scale, with a higher score for TTTS than for DC (p = 0.005), and UMC (p = 0.007) at the same GA. 30% of mothers in TTTS group have PTSD during pregnancy. 50% of TTTS- patients present an anxiety score over the threshold (STAI-Scale), with a score significantly higher in TTTS than in UMC (p<0.001) or DC (p<0.001). The proportion of subject with a STAI–State over the threshold is also significantly higher in TTTS than in DC at 20 GW (p = 0.01) and at 26 GW (p<0.05). The STAI-state scores in UMC and DC increase progressively during pregnancy while they decrease significantly in TTTS. TTTS announcement constitutes a traumatic event during a pregnancy with an important risk of PTSD, high level of anxiety and an alteration of the prenatal attachment. These results should guide the psychological support provided to these patients.

Results:Of 329 twin pregnancies, 88 were MC. Of 78 MC twins with known outcomes, the rate of TOP, miscarriage (<24 weeks), stillbirth, neonatal death, at least one survival (ALOS), was 3.3%, 8.6%, 1.3%, 1.3%, 89.3% respectively. Compared to TTTS, sIUGR was more common (26.9%vs 12.7%), diagnosed and delivered at a later median gestation (27 vs 19 weeks; 35 vs 31 weeks), associated with a lower preterm delivery before 32 weeks (5.9% vs 57.1%; P = 0.006), and a higher ALOS rate (94.4% vs 66.7%; P = 0.06). Of 21 sIUGR, four had persistent and one had intermittent absent end-diastolic flow. Bipolar cord coagulation was performed in one case before 24 weeks. Without IUGR or TTTS, ALOS rate was 100% after 24 weeks.Of 10 TTTS, eight were stage I while two were stage II at first presentation. Four were subsequently treated by laser photocoagulation of placental anastomoses, one by amnioreduction, and the remaining five conservatively. The median (IQR) diagnosis to delivery interval was 10.3 (12.6) weeks. Conclusions: Fetal loss is common in MC twins before than after 24 weeks. sIUGR is more common and associated with a better perinatal outcomes than TTTS. OP21.05Twin-to-twin transfusion syndrome and prenatal attachment