Davis Nicole L, Hoyert Donna L, Goodman David A, Hirai Ashley H, Callaghan William M
Division of Reproductive Health, Centers for Disease Control and Prevention, Atlanta, GA.
National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, MD.
Am J Obstet Gynecol. 2017 Sep;217(3):352.e1-352.e7. doi: 10.1016/j.ajog.2017.04.042. Epub 2017 May 5.
Maternal mortality ratios (MMR) appear to have increased in the United States over the last decade. Three potential contributing factors are (1) a shifting maternal age distribution, (2) changes in age-specific MMR, and (3) the addition of a checkbox indicating recent pregnancy on the death certificate.
To determine the contribution of increasing maternal age on changes in MMR from 1978 to 2012 and estimate the contribution of the pregnancy checkbox on increases in MMR over the last decade.
Kitagawa decomposition analyses were conducted to partition the maternal age contribution to the MMR increase into 2 components: changes due to a shifting maternal age distribution and changes due to greater age-specific mortality ratios. We used National Vital Statistics System natality and mortality data. The following 5-year groupings were used: 1978-1982, 1988-1992, 1998-2002, and 2008-2012. Changes in age-specific MMRs among states that adopted the standard pregnancy checkbox onto their death certificate before 2008 (n = 23) were compared with states that had not adopted the standard pregnancy checkbox on their death certificate by the end of 2012 (n = 11) to estimate the percentage increase in the MMR due to the pregnancy checkbox.
Overall US MMRs for 1978-1982, 1988-1992, and 1998-2002 were 9.0, 8.1, and 9.1 deaths per 100,000 live births, respectively. There was a modest increase in the MMR between 1998-2002 and 2008-2012 in the 11 states that had not adopted the standard pregnancy checkbox on their death certificate by the end of 2012 (8.6 and 9.9 deaths per 100,000, respectively). However, the MMR more than doubled between 1998-2002 and 2008-2012 in the 23 states that adopted the standard pregnancy checkbox (9.0-22.4); this dramatic increase was almost entirely attributable to increases in age-specific MMRs (94.9%) as opposed to increases in maternal age (5.1%), with an estimated 90% of the observed change reflecting the change in maternal death identification rather than a real change in age-specific rates alone. Of all age categories, women ages 40 and older in states that adopted the standard pregnancy checkbox had the largest increase in MMR-from 31.9 to 200.5-a relative increase of 528%, which accounted for nearly one third of the overall increase. An estimated 28.8% of the observed change was potentially due to maternal death misclassification among women ≥40 years.
Increasing age-specific maternal mortality seems to be contributing more heavily than a changing maternal age distribution to recent increases in MMR. In states with the standard pregnancy checkbox, the vast majority of the observed change in MMR over the last decade was estimated to be due to the pregnancy checkbox, with the greatest change in MMR occurring in women ages ≥40 years. The addition of a pregnancy checkbox on state death certificates appears to be increasing case identification but also may be leading to maternal death misclassification, particularly for women ages ≥40 years.
在过去十年中，美国的孕产妇死亡率（MMR）似乎有所上升。三个潜在的促成因素是：（1）孕产妇年龄分布的变化；（2）特定年龄组MMR的变化；（3）死亡证明上增加了一个表明近期怀孕的复选框。
确定1978年至2012年孕产妇年龄增加对MMR变化的影响，并估计怀孕复选框对过去十年MMR上升的影响。
进行了北川分解分析，将孕产妇年龄对MMR上升的影响分为两个部分：由于孕产妇年龄分布变化导致的变化和由于特定年龄组死亡率上升导致的变化。我们使用了国家生命统计系统的出生和死亡数据。采用了以下5年分组：1978 - 1982年、1988 - 1992年、1998 - 2002年和2008 - 2012年。将2008年前在死亡证明上采用标准怀孕复选框的州（n = 23）与到2012年底仍未在死亡证明上采用标准怀孕复选框的州（n = 11）的特定年龄组MMR变化进行比较，以估计怀孕复选框导致的MMR上升百分比。
1978 - 1982年、1988 - 1992年和1998 - 2002年美国的总体MMR分别为每10万例活产9.0例、8.1例和9.1例死亡。到2012年底仍未在死亡证明上采用标准怀孕复选框的11个州，在1998 - 2002年至2008 - 2012年期间MMR有适度上升（分别为每10万例8.6例和9.9例死亡）。然而，在采用标准怀孕复选框的23个州，MMR在1998 - 2002年至2008 - 2012年期间增加了一倍多（从9.0升至22.4）；这种显著增加几乎完全归因于特定年龄组MMR的上升（94.9%），而非孕产妇年龄的增加（5.1%），估计观察到的变化中有90%反映了孕产妇死亡识别的变化，而不仅仅是特定年龄组死亡率的实际变化。在所有年龄组中，采用标准怀孕复选框的州中40岁及以上的女性MMR上升幅度最大——从31.9升至200.5——相对上升了528%，占总体上升的近三分之一。估计观察到的变化中有28.8%可能是由于40岁及以上女性的孕产妇死亡误分类。
近期MMR的上升中，特定年龄组孕产妇死亡率的增加似乎比孕产妇年龄分布的变化贡献更大。在有标准怀孕复选框的州，估计过去十年观察到的MMR变化绝大多数归因于怀孕复选框，MMR变化最大的是40岁及以上的女性。州死亡证明上增加怀孕复选框似乎增加了病例识别，但也可能导致孕产妇死亡误分类，特别是对于40岁及以上的女性。
