he acuity of hypotension following the death of one twin with TTTS makes successful intervention for the survivor nearly impossible. Even with delivery immediately ater a cotwin demise is recognized, the hypotension that occurs at the moment of death has likely already caused irreversible brain damage (Langer, 1997; Wada, 1998). s such, immediate delivery is not considered beneficial in the absence of another indication.
Diagnosis. he criteria used to diagnose and classiy varying severities of TTTS have dramatically changed. Previously, weight discordancy and hemoglobin diferences in monochorionic twins were calculated. However, in many cases, these are late findings. According to the Society for Maternal-Fetal Medicine (2013), TTTS is diagnosed based on two so nographic criteria. First, a monochorionic diamnionic pregnancy is identified. Second, hydramnios defined by a largest vertical pocket > 8 em in one sac and oligohydramnios defined by a largest vertical pocket <2 em in the other twin is found. Only 15 percent of pregnancies complicated by lesser degrees of luid imbalance progress to TTTS (Huber, 2006). Although growth discordance or growth restriction may be found with TTTS, these per se are not considered diagnostic criteria.
Organizations that include the American College of Obstetricians and Gynecologists (2016), Society for Maternal-Fetal Medicine (2013), and North American Fetal herapy Network (Emery, 2015) recommend sonography surveillance of pregnancies at risk for TTTS. To aid earlier identification of amnionic luid abnormalities and other complications of monochorionic twins, these examinations begin at approximately 16 weeks' gestation, and subsequent studies are considered every 2 weeks. Once identiied, TTTS is typically classiied by the Quintero (1999) staging system (Fig. 45-21):
Stage I-discordant amnionic fluid volumes as described in the earlier paragraph, but urine is still visible sonographically within the bladder of the donor twin
Stage II-criteria of stage I, but urine is not visible within the donor bladder
Stage III-criteria of stage II and abnormal Doppler studies of the umbilical artery, ductus venosus, or umbilical vein
Stage V-demise of either fetus.
In addition to these criteria, evidence suggests that cardiac function of the recipient twin correlates with fetal outcome (Crombleholme, 2007). Although fetal echocardiographic indings are not part of the Quintero staging system, many centers routinely perform fetal echocardiography for TTTS. heoretically, earlier diagnosis of cardiomyopathy in the recipient twin may identiy pregnancies that would beneit from early intervention. One system for evaluating cardiac function-the myocardial peormance index (MPI) or Tei index-is a Doppler index of ventricular function calculated for each ventricle (Michelfelder, 2007). lthough scoring systems that include assessment of cardiac function have been developed, their usefulness to predict outcomes remains controversial (Society for Maternal-Fetal Medicine, 2013).
Management and Prognosis. he prognosis for mulrifetal gestations complicated by TTTS is related to Quintero stage and gestational age at presentation. More than three fourths of stage I cases have been reported to remain stable or regress without intervention. Conversely, outcomes in those identiied at stage III or higher are much worse, and the perinatal loss rate is 70 to 100 percent without intervention (Society for Maternal-Fetal Medicine, 2013). At Parkland Hospital, among expectantly managed pregnancies with TTTS, most had early disease at diagnosis, and 50 percent of stage I cases progressed (Duryea, 2016).