Perinatology Research Branch, NICHD, NIH, DHHS, Bethesda, MD, USA.
J Perinat Med. 2013 Jan;41(1):27-44. doi: 10.1515/jpm-2012-0272.
Preterm birth is the leading cause of perinatal morbidity and mortality worldwide, and is the most important challenge to modern obstetrics. A major obstacle has been that preterm birth is treated (implicitly or explicitly) as a single condition. Two thirds of preterm births occur after the spontaneous onset of labor, and the remaining one third after "indicated" preterm birth; however, the causes of spontaneous preterm labor and "indicated" preterm birth are different. Spontaneous preterm birth is a syndrome caused by multiple etiologies, one of which is a decline in progesterone action, which induces cervical ripening. A sonographic short cervix (identified in the midtrimester) is a powerful predictor of spontaneous preterm delivery. Randomized clinical trials and individual patient meta-analyses have shown that vaginal progesterone reduces the rate of preterm delivery at <33 weeks of gestation by 44%, along with the rate of admission to the neonatal intensive care unit, respiratory distress syndrome, requirement for mechanical ventilation, and composite neonatal morbidity/mortality score. There is no evidence that 17-α-hydroxyprogesterone caproate can reduce the rate of preterm delivery in women with a short cervix, and therefore, the compound of choice is natural progesterone (not the synthetic progestin). Routine assessment of the risk of preterm birth with cervical ultrasound coupled with vaginal progesterone for women with a short cervix is cost-effective, and the implementation of such a policy is urgently needed. Vaginal progesterone is as effective as cervical cerclage in reducing the rate of preterm delivery in women with a singleton gestation, history of preterm birth, and a short cervix (<25 mm).
早产是全球围产期发病率和死亡率的主要原因，也是现代产科面临的最重要挑战。主要障碍之一是早产被（隐含或明确地）视为单一病症。三分之二的早产发生在自发性分娩开始后，其余三分之一发生在“有指征”的早产之后；然而，自发性早产和“有指征”早产的原因不同。自发性早产是一种由多种病因引起的综合征，其中之一是孕激素作用下降，导致宫颈成熟。中孕期超声检查发现的宫颈短是自发性早产的有力预测指标。随机临床试验和个体患者荟萃分析表明，阴道用孕激素可使妊娠<33 周的早产率降低 44%，同时降低新生儿重症监护病房入院率、呼吸窘迫综合征发生率、需要机械通气的发生率以及复合新生儿发病率/死亡率评分。没有证据表明 17-α-羟孕酮己酸酯可以降低宫颈短的女性的早产率，因此，首选药物是天然孕激素（不是合成孕激素）。对宫颈超声检查评估宫颈短的孕妇早产风险，并对其使用阴道用孕激素，是具有成本效益的，迫切需要实施这一政策。阴道用孕激素在降低单胎妊娠、早产史和宫颈短（<25mm）孕妇的早产率方面与宫颈环扎术同样有效。
