The Hemodynamic Change of Doppler Flow Velocimetry to Developing of Twin Growth Discordance in Relation to Placental Chorionisity, Placental Weight and Umbilical Cord Insertion

Kim, Suk Young; Kim, Gwang Jun; Yoon, Seong Jun; Lee, Sun Pyo; Lee, Ji Sung

Abstract

OBJECTIVE
To evaluate hemodynamic change in growth discordant twins using a ratio of middle cerebral artery/umbilical artery resistance index and to assess the relationship between Doppler hemodynamic and the influence of placental chorionisity and umbilical cord insertion.
METHODS
118 live born twin pairs whose birthweight discordance below or above 20% between March 2000 and March 2002 were included in our study. And we divided the two groups in which above 20% of growth discordance (GD) group was GD and below 20% of GD group was control. Chorionisity and umbilical cord insertion in all study subjects within 24 hours after delivery were investigated. And then we classified to monochorionic (MONO), and dichorionic (DI) placenta and the type of insertion of umbilical cord were also classified central, marginal and velamentous type. 56 of twin pairs were performed 153 Doppler flow velocimetry between smaller and larger fetus prenatally. Resistance index (RI) of middle cerebral artery and umbilical artery in each fetus were measured and standardized as a ratio of middle cerebral artery/umbilical artery (MCA/UmA). ANOVA, Mann-Whitney U test, and chi-square test, were performed and p<0.05 was considered as statistically significant.
RESULTS
Mean birthweight in monochorionic twins had lighter than those of dichorionic twins (p<0.01). The mean growth discordant ratios were 14.1% in monochorionic twin and 12.1% in dichorionic twins. In monochorionic twin, the smaller fetus in GD group showed lower value of MCA/UmA RI ratio than those of the larger fetus, significantly (1.09 vs. 1.28 p<0.05). And in monochorionic twins, the smaller fetus in GD group showed lower value of MCA/UmA RI ratio than the smaller fetus in control group, significantly (1.09 vs. 1.27 p<0.05). The placental weight in dichorionic twin was correlated the birthweight in infants in GD group, positively. Monochorionic twins in GD group had a significantly higher incidence of peripheral cord insertion than those of dichorionic twins in GD group (50.0% vs. 35.7% p<0.01). But dichorionic twins had a significantly higher incidence of central cord insertion than those of monochorionic twins in control group (69.2 vs. 57.4 p<0.05).
CONCLUSION
The higher middle cerebral artery blood flows in smaller fetuses of monochorionic twins proved to be circulatory redistribution of the fetus in inadequate intrauterine condition. And these change of middle cerebral blood flow might be understood the part of mechanisms fetal growth and adaptation. Placental weight, number and umbilical cord insertion were also important factors which affected to develop the growth discordance of twin pregnancy.