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

这可以在产前检测DNA成，如绒毛绒毛取样或羊穿刺术。

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.

气体和营养物在薄绒绒毛组织层之间扩散，在基蜕和静脉之间来回移动。