The aim of this study is to evaluate perfusional changes in brain and placenta of omphalopagus conjoined twins and to compare them with singleton fetuses by using diffusion weighted imaging and apparent diffusion coefficient. Fetal MRIs of 28-week-old omphalopagus conjoined twins with a shared liver with two separate gallbladders and portal and hepatic venous systems and three singleton fetuses with unilateral borderline ventriculomegaly at the same gestational week as control group were enrolled retrospectively. There was a significant decrease in ADC values of brain regions (p=0.018) and placenta (p=0.005) of conjoined twins compared to the control group. The decreased ADC values in placenta and brain regions in conjoined twins might be due to decreased placental perfusion compared to singleton pregnancy. Our results would be a keystone for future studies which will compare larger group of monochorionic multiple pregnancies with singleton pregnancies.