早剥的具体原因尚不清楚。但是早剥可能由于多种途径引起。
直接的腹部外伤可能引起胎盘早剥。
非直接的外伤可能使胎盘从子宫壁剥离。
可卡因引起血管痉挛可能导致胎盘分离。
胎盘的病理检查提示胎盘剥离通常存在慢性炎症,说明早剥也通常是长期慢性的最终结果。[8]Ananth CV, Oyelese Y, Prasad V, et al. Evidence of placental abruption as a chronic process: associations with vaginal bleeding early in pregnancy and placental lesions. Eur J Obstet Gynecol Reprod Biol. 2006;128:15-21.http://www.ncbi.nlm.nih.gov/pubmed/16513243?tool=bestpractice.com相反的,急性事件如可卡因使用或外伤,尤其是MVA,可能引起正常妊娠的胎盘剥离。据观察,23-24周异常子宫动脉多普勒血流可能引起后期妊娠早剥的风险升高,支持了某些患者长期过程的理论。[9]Kurdi W, Campbell S, Aquilina J, et al. The role of color Doppler imaging of the uterine arteries at 20 weeks' gestation in stratifying antenatal care. Ultrasound Obstet Gynecol. 1998;12:339-345.http://www.ncbi.nlm.nih.gov/pubmed/9819873?tool=bestpractice.com[10]Harrington K, Cooper D, Lees C, et al. Doppler ultrasound of the uterine arteries: the importance of bilateral notching in the prediction of pre-eclampsia, placental abruption or delivery of a small-for-gestational-age baby. Ultrasound Obstet Gynecol. 1996;7:182-188.http://www.ncbi.nlm.nih.gov/pubmed/8705410?tool=bestpractice.com
一项关于发生早剥的女性胎盘床活检的研究发现胎盘滋养细胞侵袭不足,这一表现与子痫前期病变相似,在五分之三的女性都存在。[11]Dommisse J, Tiltman AJ. Placental bed biopsies in placental abruption. Br J Obstet Gynaecol. 1992;99:651-654.http://www.ncbi.nlm.nih.gov/pubmed/1390469?tool=bestpractice.com子痫前期、胎盘早剥或宫内生长受限的女性在下次妊娠时发生这些并发症的风险仍高。[12]Ananth CV, Peltier MR, Chavez MR, et al. Recurrence of ischemic placental disease. Obstet Gynecol. 2007;110:128-133.http://www.ncbi.nlm.nih.gov/pubmed/17601907?tool=bestpractice.com事实上,所有的3种情况都和易栓症有关,这种情况可能增加胎盘内异常凝血的倾向。[13]Brenner B. Clinical management of thrombophilia-related placental vascular complications. Blood. 2004;103:4003-4009.http://www.ncbi.nlm.nih.gov/pubmed/14962907?tool=bestpractice.com这也提示这3种情况占有较大比例,尤其是在早产时,属于胎盘缺血性疾病,并具有共同的病因。[12]Ananth CV, Peltier MR, Chavez MR, et al. Recurrence of ischemic placental disease. Obstet Gynecol. 2007;110:128-133.http://www.ncbi.nlm.nih.gov/pubmed/17601907?tool=bestpractice.com[13]Brenner B. Clinical management of thrombophilia-related placental vascular complications. Blood. 2004;103:4003-4009.http://www.ncbi.nlm.nih.gov/pubmed/14962907?tool=bestpractice.com但是,美国妇产科医师学会指南建议,发生胎盘早剥后不再进行血栓形成倾向测试,因为这似乎不会增加早剥的风险。[14]American College of Obstetricians and Gynecologists Women's Health Care Physicians. ACOG Practice Bulletin No. 138: Inherited thrombophilias in pregnancy. Obstet Gynecol. 2013;122:706-717.http://www.ncbi.nlm.nih.gov/pubmed/23963422?tool=bestpractice.com