妊娠期母体免疫监护作用下降 ,且绒毛的滋养细胞并非完整无缺 ,其上可有小的裂隙 ,因此病原体可自颈管上升 ,经胎膜而导致宫内感染 ,即上行性感染 ;或经母血到胎盘 ,以及罕见经羊水穿刺、绒毛采样、羊膜腔镜、宫腔内胎儿脐血采样、宫腔内胎儿输血或手术而致感染 ,即血行性感染[ Pregnancy maternal immune guardianship decreased, and villous trophoblast cells are not intact, there may be a small gap, so the pathogen can rise from the neck, the intrauterine infection caused by the fetal membrane, that is, upwards infection; or by the mother Blood to the placenta, and rare by amniocentesis, villus sampling, amnioscopy, intrauterine fetal umbilical cord blood sampling, intrauterine fetal blood transfusion or surgery and infection, that is, hematogenous infections [