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Placental vascular anastomoses in twins lead to a shared circulation and may subsequently enable the development of severe complications such as twin-twin transfusion syndrome (TTTS) and twin anemiapolycythemia sequence (TAPS). The presence of vascular anastomoses has frequently and systematically been studied in monochorionic (MC) placentas, but only rarely in dichorionic (DC) placentas. The aim of this study was to compare the prevalence of vascular anastomoses and evaluate the sharing discordance in MC and DC placentas. All consecutive placentas of MC and DC twins delivered at the Leiden University Medical Center (the Netherlands) and Medical University of Warsaw (Poland) from 2012 to 2015 were routinely injected with colored dye and included in the study. We excluded twin pregnancies treated with fetoscopic laser surgery. A total of 258 placentas were analyzed in this study, including 134 MC placentas and 124 DC placentas. Vascular anastomoses were present in 99% (133/134) of MC placentas and 0% of DC placentas (p < .01). Placental share discordance between MC twins was significantly larger compared to DC twins, 19.8 (interquartile range [IQR] 8.1-33.3) and 10.8 (IQR 6.2-19.0), respectively (p < .01). Vascular anastomoses associated complications occurred in 16% (22/134) MC twins. Our findings show that vascular anastomoses are almost ubiquitous in MC placentas, but non-existent in DC placentas. In addition, unequal placental sharing appears to be more common in MC than in DC placentas.

Numerous studies have demonstrated that prenatal stress disturbs the hippocampal-mediated learning and memory processes in offspring. The underlying mechanisms for this effect, however, remain vague. It is well documented that N-methyl-D-aspartate (NMDA) receptors play a pivotal role in learning and memory, which are related to dynamically trafficking and regulating NMDA receptors by their response motor proteins. Over the past few years, increasing numbers of studies have elucidated that hippocampal-mediated learning and memory are regulated by KIF17 (kinesin superfamily motor protein 17), which specifically transports and regulates the NMDA receptor subunit NR2B in hippocampal neurons. The present study shows the influence of prenatal stress on KIF17 and NR2B expression and hippocampal NR2A/NR2B ratio partially reflecting function of KIF17, using mice as models. It was found that prenatal stress significantly decreased the hippocampal KIF17 and NR2B level in offspring at postnatal stages of 3 weeks and 9 weeks. Moreover, hippocampal KIF17 in the prenatally stressed pups continued to be weakened even after serial Morris water maze trainings, but not NR2B. Finally, the synaptic NR2A/NR2B level was upregulated in offspring exposed to prenatal stress, which revealed the dysfunction of KIF17. Thus, we conclude that prenatal stress leads to long-lasting deterioration of the expression and function of hippocampal KIF17 in offspring, which may be related to deficits of spatial cognition caused by prenatal stress. These data underpin the hypotheses that a physiopathology of neurodevelopmental origin in early life leads to defects in learning and memory in later life.

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Placental damage is positively associated with more laser energy but negatively associated with higher power setting. More placental damage was associated with a lower GA at birth, shorter laser-to-delivery interval and higher PPROM rate. Whether these results should lead to a change in surgical technique requires more research, both further ex-vivo experiments on human placentas and clinical studies.