Vorherr H
Am J Obstet Gynecol. 1975 Sep 1;123(1):67-103. doi: 10.1016/0002-9378(75)90951-5.
As pregnancy extends post term, incidence of placental insufficiency, fetal postmaturity (dysmaturity), and fetal perinatal death increases rapidly as a consequence of reduced respiratory and nutritive placental function. Despite a compensatory fetoplacental respiratory reserve capacity, fetal distress is observed in about one third of postterm pregnancies. On a biochemical level, placental pathophysiology in postterm-postmaturity pregnancies is not well understood. Postmaturity is correlated with increased incidence of placental lesions, fetal hypoxia-asphyxia, intrauterine growth retardation, increased perinatal death, and neonatal morbidity. Early diagnosis of fetal postmaturity is difficult because currently applied test methods allow recognition only when placental insufficiency is far progressed. Therefore, in postterm gravidas with a favorable cervix, induction of labor should be considered; in older primigravidas, in whom fetal losses may be sevenfold increased, or in multiparas with a history of obstetric complications, pregnancy may require termination by cesarean section. Pregnancy may be allowed to continue under close supervision in cases of uncertainty of duration of gestation, in gravidas carrying small babies, in young primigravidas, and in multigravidas in whom placentofetal function tests are normal. As long as fetal scalp blood sampling during labor does not show fetal acidosis, despite abnormal fetal heart rate pattern and meconium release, vaginal delivery may be attempted when deemed possible within a few hours. In parturients attention must be paid to the extent of uterine activity and type of medication; lateral positioning of the gravida and maternal oxygen breathing, facilitating fetal oxygen supply, are important features. Because during bearing-down efforts placentofetal respiratory reserves of postterm gravidas may become further compromised, immediate delivery by forceps or vacuum extraction may be considered. After delivery the umbilical cord should not be clamped immediately in order to allow increased fetal blood supply and to counteract fetal hypovolemia. Dysmature newborn infants require special care by the neonatologist.
随着孕期超过预产期，由于胎盘呼吸和营养功能下降，胎盘功能不全、胎儿过熟（发育异常）及胎儿围产期死亡的发生率会迅速上升。尽管胎儿-胎盘具有代偿性呼吸储备能力，但约三分之一的过期妊娠会出现胎儿窘迫。在生化水平上，过期-过熟妊娠的胎盘病理生理学尚未完全明确。过熟与胎盘病变、胎儿缺氧-窒息、宫内生长受限、围产期死亡增加及新生儿发病率上升有关。胎儿过熟的早期诊断困难，因为目前应用的检测方法只有在胎盘功能不全进展到很严重时才能识别。因此，对于宫颈条件良好的过期孕妇，应考虑引产；对于年龄较大的初产妇（其胎儿丢失风险可能增加7倍）或有产科并发症史的经产妇，可能需要剖宫产终止妊娠。对于妊娠期限不确定的孕妇、怀有小胎儿的孕妇、年轻初产妇以及胎盘-胎儿功能检查正常的经产妇，在密切监测下可允许继续妊娠。只要产程中胎儿头皮血取样未显示胎儿酸中毒，尽管胎儿心率异常且有胎粪排出，若在数小时内认为有可能，可尝试经阴道分娩。对于产妇，必须注意子宫活动程度及用药类型；孕妇侧卧位及母体吸氧以促进胎儿供氧很重要。因为在用力分娩时，过期孕妇的胎儿-胎盘呼吸储备可能会进一步受损，可考虑立即用产钳或真空吸引器助产。分娩后不应立即夹紧脐带，以便增加胎儿血供并对抗胎儿低血容量。发育异常的新生儿需要新生儿科医生给予特殊护理。
