P12.15: Discordant pathological findings in multiple pregnancies from the genetic point of view

In association with the rapid progress in the methods of assisted reproduction, the Hellin’s rule from the 1895 is not valid any more. During our routine prenatal screening examinations a frequency of 1 : 67 for twin pregnancy and 1 : 1800 for triplet were noted. With the increasing number of multiple pregnancies the risk of congenital abnormalities and fetal defects is raising up in either one or all fetuses. In the last 10 years we have had 23 cases of discordant pregnancies in which only one of the fetuses was affected. The risk for any congenital abnormality in the general population is 2.5–3%; we have found of 6.6% discordant affected fetuses in our patients. We divided our group according to the type of chorionicity into monoamnionic monochorionic, biamnionic monochorionic and biamnionic bichorionic, when the last one is about 82%. Multicystic dysplasia type Potter II was only coincident finding in which both fetuses were affected. Interestingly both fetuses with Di George syndrome showed different type of defect on DNA analysis. Parallel when identical systems were affected but the degree of affection or identification of additional defects was different. The detection rate of severe congenital abnormalities was 17% and 61% upto16 and 24 weeks in pregnancy respectively. A later detection of abnormalities was when pathological marker has to develop mostly in the 3rd trimester. During genetic analysis the chromosomal set up possible in 25%. In two other cases where one of the parents was a carrier for unbalanced translocation both fetuses have had the same defect but were born healthy. Polygeny type of heredity was the most common cause of detected defects in which 20% have had serious genetic history. The question is still why only one fetus is affected, or in case of both why they are affected differently. This study would be suitable for assessment of the mutagenic environment and may be the individual susceptibility.