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Monochorionic twin pregnancy and its physiological cardiac dysfunction during 3rd trimester

Presented: ICMH

Published: To be published in ISPUG after the ICMH

Objectives: Present knowledge about maternal hemodynamics in twin pregnancies is that they are characterized by hyperdinamic circulation, increased blood volume, increased cardiac output (CO), and reduced total vascular resistance (TVR). All these changes are more evident in a twin pregnancy than in single pregnancy. The aim of our study was to assess the hemodynamic changes in monochorionic (MC) and dichorionic (DC) twin pregnancies, in order to understand how the chorionicity can influence cardiac function.

Methods: we enrolled 58 twin pregnancies at 2nd trimester and we divided them into two groups: dichorionic (n: 38) and monochorionic (n: 20) twin pregnancies. We performed hemodynamic assessment with USCOM method and analyzed blood test values at the time of enrollment. The evaluation was repeated during the third trimester.

Results: Our two groups are similar in terms of maternal age, ethnicity, BMI. Dichorionic pregnancies are more frequently achieved through assisted reproductive technologies. The mean gestational age at the enrollment is 22 weeks, and the second evaluation (in 3rd trimester) is performed at about 31-32 weeks. There are no differences in terms of blood values. As shown in the table, during the 2nd trimester the hemodynamic profile is similar in the two groups, while during the 3rd trimester, monochorionic twin pregnancies present increased TVR, reduced CO and inotropism value (INO) and increased potential to kinetic energy ratio (PKR). On the contrary, dichorionic twin pregnancies maintain a low resistance hemodynamic profile during the 3rd trimester.

Conclusions: During the 3rd trimester, monochorionic twin pregnancies have high TVR, low CO and INO, and a hypodynamic circulation. This condition of cardiac dysfunction probably reflects the fact that monochorionic twin pregnancies (characterized by a single placental bed) have an increased blood volume in their bloodstream.