P15.05: First trimester crown–rump length in twin pregnancy as a predictor of birthweight discordance

Abstract

Objectives: To evaluate the sensitivity of serial measurements of middle cerebral artery peak systolic velocity (MCAPSV) in the prediction of twin anemia polycythemia sequence (TAPS). Methods: MCA and umbilical artery (UA) Dopplers were prospectively measured every one to three weeks between 24 and 37 weeks' gestation on all monochorionic (MC) twin by maternal fetal medicine team in our specialised twin clinics from June 2013 to March 2015. We used the MCAPSV cut offs of > 1.5 and < 0.8 MoM to predict anemia and polycythemia respectively. Hemogoblin (Hb) levels and retriculocyte counts were measured for both twins at or shortly after birth. Results: A total of 76 pairs of MC twins and 372 Doppler measurements were studied. Median delivery was at 35 + 7 weeks and intertwin difference in Hb at birth was 1.5 g/dl. Three (4.2%) of 72 pairs with known outcomes had spontaneous stage 1 TAPS confirmed on postnatal criteria. Discrepancy in MCAPSV was noted in case 1 at 27 weeks with 1.57 and 0.7 MoM for twin A and B respectively, but resolved spontaneously for 3 weeks and then reappeared at 31 weeks with 1.74 and 1 MoM for twin A and B respectively. After Caesarean delivery, Hb was 9.5 and 18.4 g/dl for twin A and B respectively with an intertwin reticulocyte count ratio (ircr) of 2.8. Case 2 was delivered at 34 weeks for selective IUGR. The Hb level of twin A and B was 11.6 and 20 g/dl respectively with small < 1mm placental arteriovenous anastomosis identified after delivery. However, the corresponding MCAPSV two days before birth was 1 and 0.66 MoM respectively. Case 3 presented as reduced fetal movement at 31 weeks and hydropic twin A and was then delivered for sinusoidal fetal heart pattern. The Hb of twin A and B was 8.3 and 21.7 g/dl respectively with ircr 2.3. However, MCAPSV was 0.57 MoM for both twins 12 days before delivery. Conclusions: It seems that the sensitivity of using serial measurements of MCAPSV alone to predict TAPS may not be high. MCAPSV changes are quite dynamic. P15.05First trimester crown-rump length in twin pregnancy as a predictor of birthweight discordance