Complex morphological and computed tomographic characteristics of vascularization of monochorionic diamniotic placentas with discordant weight of newborns

BACKGROUND: Twin pregnancies compared to singleton pregnancies are characterized by a higher incidence of complications, particularly fetal growth retardation [1]. The main causes of discordance and fetal growth retardation are considered to be differences in the size of placental sites, leading to uneven metabolism of substances and blood, as well as disorders of fetal blood supply caused by vascular anastomoses in the placenta [2, 3]. Computed tomography with the administration of contrast agents can be an effective method to assess the angioarchitectonics and vascularization of the placenta after delivery [4].

AIM: The aim of this study is to conduct a comprehensive computed tomography and morphological evaluation of the vascularization features of monochorionic diamniotic placentas with discordant neonatal weight.

MATERIALS AND METHODS: This study was based on the analysis of 33 monochorionic diamniotic placentas obtained after delivery at 27–37 weeks of gestation using the original complex computed tomography and morphological method of investigation [5]. Upon obtaining the placenta, its mass and size of placental sites were determined, as well as the type of attachment, length, diameter, and degree of cord tortuosity. Prior to the computed tomography examination, the umbilical cord and its major branches were cleared of blood clots. The placenta was then immersed in a 10% hypertonic sodium chloride solution and placed on hygroscopic material. Subsequently, contrast dye mixtures of varying colors and concentrations were gradually injected into the unpaired umbilical vein, followed by the umbilical arteries in a sequential manner. The contrast dye mixtures consisted of a water-soluble radiopaque contrast agent, iodixanol, in an aqueous solution of gouache dye. The concentration of the contrast agent in the mixture for injection into the umbilical arteries was 70%, while in the vein it was 15%. The first and second placentae were injected with red and yellow gouache dyes, respectively, into the arteries of the umbilical cord, while blue and green gouache dyes were used for the veins. Following each injection of the contrast dye mixture into the umbilical cord vessel, a visual assessment of the vessel’s branching was conducted, followed by computed tomography on a Toshiba Aquilion ONE 640 (Pediatric 0.5 software package according to the Abdomen Baby study protocol). The final stage involved a traditional macroscopic and microscopic examination of the placenta [6].

RESULTS: The study revealed that the mean value of birth weight discordance in twins was 22.7 ± 2.1%, while placental site discordance was 26.6 ± 5.0%. Vascular anastomoses were identified in 74.2% of twin placentas. Of these, 19 cases exhibited one anastomosis, three cases demonstrated two anastomoses, and one case exhibited five anastomoses. Arterio-arterial anastomoses were observed with greater frequency, while veno-venous and arteriovenous anastomoses were observed with less frequency. The average diameter was 3.7 ± 0.15 mm for arterio-arterial anastomoses, 4.2 ± 0.23 mm for arteriovenous anastomoses, and 4.6 ± 0.26 mm for venous-venous anastomoses.

CONCLUSIONS: The use of the developed complex method, which includes computed tomography and the subsequent construction of three-dimensional models of placental vessels and spectral color maps, allows for the visualization of the features of placental vascularization, as well as the assessment of the type and size of existing anastomoses. In monochorionic diamniotic placentas with fetal discordance, a high frequency of abnormal umbilical cord attachment and vascular anastomoses was detected.