This can also be done prenatally by testing fetal DNA obtained through either chorionic villus sampling or amniocentesis.

这可前通过检测胎儿DNA完成，如绒绒取样或羊穿刺术。

Gases and nutrients move back and forth between the decidua basalis and the fetal veins, by diffusing through the tissue layer of the thin chorionic villi.

气体和营养物质通过薄绒绒层之间扩散，基蜕和胎儿静脉之间来回移动。