出生体重增加影响正常分娩曲线

圣迭戈(EGMN)——随着出生体重的增加，成功阴道分娩患者和最终接受剖宫产手术患者的分娩进展均变缓。

“自从20世纪50年代以来，产科医生一直在借助Friedman分娩曲线对正常和异常分娩情况进行解释，”首席研究者Heidi K. Leftwich, D.O.在美国妇产学会年会上说：“然而，现在我们面对的患者人群已与当时有很大不同。更多产妇患有肥胖症，对第二产程的管理不再像以前那么积极，我们更多使用硬膜外麻醉，产妇的年龄更大。”随着剖宫产率的攀升，“当前研究关注的是可能改变分娩曲线的变量，并质疑一条分娩曲线适用于所有妇女的观念”。

伊利诺斯州立大学妇产科母胎医学研究员Leftwich博士及其同事对安全分娩联盟电子数据进行了回顾性分析，这是Eunice Kennedy Shriver美国国立儿童健康和人类发展研究院(NICHD)和美国国立卫生研究院(NIH)牵头于2002~2008年间在12个临床中心进行的一项对分娩和接产实践的观察性研究，主要目的是确定出生体重是否改变了初产妇和经产妇的分娩曲线。入选标准包括头先露、单胎妊娠、孕龄³34周、接受了³2次宫颈检查的患者。排除胎儿畸形、择期再次剖宫产和缺乏出生体重数据的患者。研究者以体重每增加500 g为间隔，确立了5个出生体重分类：不足2,500 g(第1类)、2,500~2,999 g(第2类)、3,000~3,499 g(第3类)、3,500~3,999 g(第4类)以及³4,000 g(第5类)。他们使用间隔删失回归的方法估算分娩持续时间或“时间跨度”，并用重复指标分析构建不同产次和不同体重分类的平均分娩曲线。“时间跨度更大程度上是宫颈每扩张1 cm所需时间的近似值，我们是根据入院以及分娩过程中所做的检查对宫颈扩张情况进行分层的。”

结果显示，共有146,904份产妇医疗记录符合入选标准。第1、2、3、4和5组中剖宫产分娩率分别为21%、14%、14%、17%和25%。Leftwich博士报告，在初产妇中，无论阴道分娩还是剖宫产，时间跨度均随出生体重增加而延长(P<0.001)。在经产妇中，无论经阴道还是剖宫产分娩，宫颈扩张5~8 cm的时间跨度均随出生体重增加而延长(P<0.001)。“宫颈扩张8~10 cm的时间跨度仍随出生体重增加而延长，但因为进行的宫颈检查很少而未达到统计学意义。”

该研究由Eunice Kennedy Shriver美国国立儿童健康和人类发展研究院的一个内部研究项目协议以及芝加哥市伊利诺斯州立大学临床和转化科学的一项奖金资助。Leftwich博士披露无相关利益冲突。

BY DOUG BRUNK
Elsevier Global Medical News
Breaking News

SAN DIEGO (EGMN) – As birth weight increases, progression in labor was slower both in successful trial of labor patients and in patients who ultimately had cesarean deliveries.

The findings come from a retrospective review of electronic data from the Consortium on Safe Labor, an observational study of labor and delivery practices led by the Eunice Kennedy Shriver U.S. National Institute of Child Health and Human Development (NICHD) and the U.S. National Institutes of Health (NIH) that was conducted at 12 clinical centers from 2002 to 2008.

“Since the 1950s, obstetricians have been using the Friedman labor curve in order to assist in interpreting normal and abnormal labor patterns,” lead study author Heidi K. Leftwich, D.O., said at the annual meeting of the American College of Obstetricians and Gynecologists.

“However, we have [a] very different patient population these days. There is more obesity, less active management of the second stage of labor, we use more epidurals, and we have an older population, with women waiting later to begin their families.”

With the cesarean section rate escalating, she continued, “current research has been focusing on variables which might alter the labor curve, and challenging the notion that one labor curve can apply to all women.”

The objective of the current study was to examine data from the Consortium on Safe Labor to determine whether birth weight alters the labor pattern in nulliparas and multiparas. Inclusion criteria consisted of patients with cephalic presentation, singleton gestation, gestational age of 34 weeks or more, who had undergone two or more cervical exams. Those patients with fetal anomalies, elective repeat cesarean section, and lacking birth weight data were excluded from the study.

The researchers created five birth weight categories separated by 500 g increments: less than 2,500 g (category 1), 2,500-2,999 g (category 2), 3,000-3,499 g (category 3), 3,500-3,999 g (category 4), and greater than or equal to 4,000 g (category 5). They used interval-censored regression to estimate the duration of labor, or “traverse times,” and repeated measures analysis to construct mean labor curves by parity as well as by birth weight categories.

“The traverse times is more of an approximation of the time it takes for the cervix to dilate a centimeter,” explained Dr. Leftwich, a fellow of maternal-fetal medicine in the department of obstetrics and gynecology at the University of Illinois at Chicago. “This is stratified by cervical dilation at admission, as well as exams performed in labor.”

A total of 146,904 maternal records met inclusion criteria. Cesarean sections occurred in 21% of group 1, 14% of group 2, 14% of group 3, 17% of group 3, and 25% of group 5. Dr. Leftwich reported that in nulliparas, traverse times increased as birth weight increased, for both vaginal and cesarean deliveries (P less than .001). In multiparas, traverse times increased as birth weight increased from 5-8 cm dilation, for both vaginal and cesarean deliveries (P less than .001). “From 8 cm-10 cm, traverse times still increased by birth weight, but this was not statistically significant secondary to minimal cervical exams,” Dr. Leftwich said.

A limitation of the study, she noted, was that “rapid progression of labor in multiparas makes traverse times less accurate for the active phase.”

The study was supported by a contract from the Intramural Research Program of the Eunice Kennedy Shriver National Institute of Child Health and Human Development and an award from the University of Illinois at Chicago Center for Clinical and Translational Science. Dr. Leftwich said that she had no relevant financial disclosures.