Division of Obstetrics and Gynecology, Instituto per I'Infanzia, Trieste, Italy.
J Perinat Med. 2010 Mar;38(2):111-9. doi: 10.1515/jpm.2010.057.
A pregnancy reaching 42 completed weeks (294 days) is defined as postterm (PT). The use of ultrasound in early pregnancy for precise dating significantly reduces the number of PT pregnancies compared to dating based on the last menstrual period. Although the fetal, maternal and neonatal risks increase beyond 41 weeks, there is no conclusive evidence that prolongation of pregnancy, per se, is the major risk factor. Other specific risk factors for adverse outcomes have been identified, the most important of which are restricted fetal growth and fetal malformations. In order to prevent PT and associated complications routine induction before 42 weeks has been proposed. There is no conclusive evidence that this policy improves fetal, maternal and neonatal outcomes as compared to expectant management. It is also unclear if the rate of cesarean sections is different between the two management strategies. After careful identification and exclusion of specific risks, it would seem appropriate to let women make an informed decision about which management they wish to undertake. There is consensus that the number of inductions necessary to possibly avoid one stillbirth is very high. If induction is preferred, procedures for cervical ripening should be used, especially in nulliparous women. Close intrapartum fetal surveillance should be offered, irrespective of whether labor was induced or not.
妊娠达到 42 周（294 天）即为过期妊娠（PT）。与基于末次月经的日期相比，早期妊娠超声检查进行精确的孕周计算可显著减少 PT 妊娠的数量。尽管超过 41 周后胎儿、产妇和新生儿的风险会增加，但没有确凿的证据表明妊娠延长本身就是主要的危险因素。已经确定了其他特定的不良结局危险因素，其中最重要的是胎儿生长受限和胎儿畸形。为了预防 PT 和相关并发症，建议在 42 周前进行常规引产。与期待管理相比，尚无确凿证据表明该策略可改善胎儿、产妇和新生儿结局。两种管理策略之间剖宫产率是否不同也尚不清楚。在仔细识别和排除特定风险后，让女性对她们希望进行的管理做出知情决策似乎是合适的。人们普遍认为，为了可能避免一次死产而需要进行的引产数量非常高。如果选择引产，应使用宫颈成熟的程序，尤其是在初产妇中。应提供密切的产时胎儿监护，无论是否诱导分娩。
