Sonography interval and the diagnosis of twin–twin transfusion syndrome

Objective: To evaluate the relationship between sonography surveillance interval and Quintero stage at diagnosis. Methods: This was a retrospective cohort study of monochorionic diamniotic pregnancies diagnosed with twin–twin transfusion syndrome (TTTS) and followed with serial sonography between 1997 and 2013. Women were divided into three cohorts: diagnosis at initial second-trimester sonogram, at a sonogram within 14 d of the prior exam, and at a sonogram greater than 14 d from the prior exam. Isolated amniotic fluid abnormalities were also recorded. Results: TTTS was identified in 48 pregnancies, with 50% of cases diagnosed at the initial sonogram, 21% within 14 d of a prior sonogram, and 29% more than 14 d from a prior sonogram. There was no association between interval and TTTS stage at diagnosis. Of 24 cases diagnosed during a follow-up sonogram, 46% had an isolated amniotic fluid abnormality preceding diagnosis. When isolated oligohydramnios (29%) or hydramnios (17%) was present, the sonography interval was significantly shorter (p = 0.003), but no difference in TTTS stage at diagnosis was found. Conclusions: Although frequent surveillance of monochorionic diamniotic pregnancies is prudent, when close follow-up of isolated fluid abnormalities was practiced, we were unable to demonstrate an effect of surveillance interval on stage of TTTS at diagnosis.