您好(hao)，正常妊娠時胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)的(de)(de)正常位置是(shi)附著(zhu)(zhu)于子(zi)宮(gong)(gong)(gong)(gong)體部的(de)(de)前(qian)(qian)壁(bi)、后壁(bi)，也(ye)可(ke)能是(shi)側壁(bi)。如果妊娠28周(zhou)以后，胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)附著(zhu)(zhu)于子(zi)宮(gong)(gong)(gong)(gong)的(de)(de)下(xia)(xia)段(duan)，胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)的(de)(de)下(xia)(xia)緣達(da)到或者是(shi)覆(fu)蓋宮(gong)(gong)(gong)(gong)頸的(de)(de)內口，位置比胎(tai)(tai)(tai)(tai)先露部還(huan)要低(di)，臨床上稱為(wei)(wei)前(qian)(qian)置胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)，也(ye)就是(shi)我(wo)們說的(de)(de)胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)低(di)。胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)低(di)最常見的(de)(de)原因(yin)是(shi)由于孕周(zhou)比較(jiao)小，此(ci)時胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)相對(dui)(dui)于宮(gong)(gong)(gong)(gong)腔面積(ji)比較(jiao)大(da)(da)，因(yin)此(ci)胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)會向下(xia)(xia)生長，而(er)(er)(er)隨著(zhu)(zhu)孕周(zhou)的(de)(de)增(zeng)加，子(zi)宮(gong)(gong)(gong)(gong)體積(ji)增(zeng)大(da)(da)，胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)會隨著(zhu)(zhu)增(zeng)大(da)(da)的(de)(de)子(zi)宮(gong)(gong)(gong)(gong)而(er)(er)(er)上移，這種情況就會由胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)低(di)置轉變(bian)為(wei)(wei)正常胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)，不用(yong)擔心。受(shou)精(jing)卵(luan)在(zai)著(zhu)(zhu)床前(qian)(qian)發育(yu)遲緩(huan)(huan)低(di)置胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)可(ke)能是(shi)因(yin)為(wei)(wei)受(shou)精(jing)卵(luan)在(zai)著(zhu)(zhu)床前(qian)(qian)發育(yu)遲緩(huan)(huan)，在(zai)到達(da)子(zi)宮(gong)(gong)(gong)(gong)腔時尚(shang)未發育(yu)到能著(zhu)(zhu)床的(de)(de)階段(duan)仍繼續(xu)下(xia)(xia)行而(er)(er)(er)植(zhi)入(ru)子(zi)宮(gong)(gong)(gong)(gong)的(de)(de)下(xia)(xia)段(duan)，在(zai)此(ci)生長發育(yu)，致胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)位置比正常低(di)。子(zi)宮(gong)(gong)(gong)(gong)內膜損害(hai)如多產、多次刮宮(gong)(gong)(gong)(gong)、剖腹產等因(yin)素，因(yin)為(wei)(wei)這些(xie)因(yin)素都可(ke)以使子(zi)宮(gong)(gong)(gong)(gong)蛻膜血(xue)管形成不全，當受(shou)精(jing)卵(luan)植(zhi)入(ru)時，血(xue)液供應不足(zu)，為(wei)(wei)滿足(zu)胎(tai)(tai)(tai)(tai)兒生長的(de)(de)需要，從母體攝取足(zu)夠的(de)(de)營養物質，從而(er)(er)(er)擴大(da)(da)胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)面積(ji)，胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)面積(ji)過大(da)(da)，可(ke)伸(shen)展至(zhi)子(zi)宮(gong)(gong)(gong)(gong)下(xia)(xia)段(duan)，而(er)(er)(er)形成胎(tai)(tai)(tai)(tai)盤(pan)(pan)(pan)(pan)(pan)低(di)。希(xi)望(wang)以上內容對(dui)(dui)您有所(suo)幫(bang)助(zhu)，祝(zhu)您生活(huo)愉快(kuai)。