ABSTRACT
OBJECTIVE: To investigate the effect of the type of placenta and the portion of umbilical cord insertion on birthweight and growth discordancy in twin pregnancies. METHODS: We selected 120 twins of 146 multiple pregnancies between March, 2000 and March, 2002, and one fetus of all cases at least weighed 500 g or more and over 24 weeks of gestation. The fetuses were included that 44 twins (88 fetuses) had monochorionic placentas and the 76 twins (152 fetuses) had dichorionic placentas. The dichorionic twins were divided into two groups; one (38 twins, 76 fetuses) showed the fused type of placenta and the other (38 twins, 76 fetuses) showed the separate type of placenta. The types of umbilical cord insertion were also divided into the central portion and the peripheral portion, the peripheral portion was defined within 2 cm of margin of placenta, and included marginal and velamentous insertion of umbilical cord. Stastical analysis were performed with Student t-test and runs test. p<0.05 was defined significantly. RESULTS: 1. The central type of umbilical cord insertion in dichorionic placenta was more frequent than that of monochorionic placenta (p<0.01). 2. The dichorionic infants, regardless the number of placenta, who weighed more than monochorionic infants at birth (p<0.01). 3. Twin pairs with over 25% of growth discordancy were 16 cases (13.3%), which included 9 cases (9/76, 11.8%) of dichorionic placenta and 7 cases (7/44, 15.9%) of monochorionic placenta. The severe growth discordancy was more commonly developed in monochorionic twins than dichorionic twins (p<0.01). 4. Perinatal deaths in twin pairs with over 25% of GD were 12 cases, which included 3 cases (3/18, 16.7%) of dichorions, and 9 cases (9/14, 64.3%) of monochorions. Therefore, perinatal death was showed more commonly in monochorinic twin infants (p<0.01). CONCLUSION: The type of umbilical cord insertion affected the birthweight of dichorionic separated infants. Monochorionic placenta attributed to more severe growth discordancy and increased perinatal death rate than the dichorionic placenta. Antenatal detection of chorionicity and the portion of umbilical cord insertion may improve the perinatal outcome.