McIntire D D, Bloom S L, Casey B M, Leveno K J
Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center, Dallas 75235-9032, USA.
N Engl J Med. 1999 Apr 22;340(16):1234-8. doi: 10.1056/NEJM199904223401603.
At any given gestational age, infants with low birth weight have relatively high morbidity and mortality. It is not known, however, whether there is a threshold weight below which morbidity and mortality are significantly greater, or whether that threshold varies with gestational age.
We analyzed the neonatal outcomes of death, five-minute Apgar score, umbilical-artery blood pH, and morbidity due to prematurity for all singleton infants delivered at Parkland Hospital, Dallas, between January 1, 1988, and August 31, 1996. A distribution of birth weights according to week of gestation at birth was created. Infants in the 26th through 75th percentiles for weight served as the reference group. Data on preterm infants (those born at 24 to 36 weeks of gestation) were analyzed separately from data on infants delivered at term (37 or more weeks of gestation).
A total of 122,754 women and adolescents delivered singleton live infants without malformations between 24 and 43 weeks of gestation. Among the 12,317 preterm infants who were analyzed, there was no specific birth-weight percentile at which morbidity and mortality increased. Among 82,361 infants who were born at term and whose birth weights were at or below the 75th percentile, however, the rate of neonatal death increased from 0.03 percent in the reference group (26th through 75th percentile for weight) to 0.3 percent for those with birth weights at or below the 3rd percentile (P<0.001). The incidence of five-minute Apgar scores of 3 or less and umbilical-artery blood pH values of 7.0 or less was approximately doubled for infants at or below the 3rd birth-weight percentile (P=0.003 and P<0.001, respectively). The incidence of intubation at birth, seizures during the first day of life, and sepsis was also significantly increased among term infants with birth weights at or below the 3rd percentile. These differences persisted after adjustment for the mother's race and parity and the infant's sex.
Mortality and morbidity are increased among infants born at term whose birth weights are at or below the 3rd percentile for their gestational age.
在任何给定的孕周，低出生体重儿的发病率和死亡率相对较高。然而，尚不清楚是否存在一个阈值体重，低于该体重发病率和死亡率会显著增加，或者该阈值是否随孕周而变化。
我们分析了1988年1月1日至1996年8月31日在达拉斯帕克兰医院分娩的所有单胎婴儿的死亡、5分钟阿氏评分、脐动脉血pH值以及早产相关发病率等新生儿结局。根据出生时的孕周创建了出生体重分布。体重处于第26至75百分位数的婴儿作为参考组。对早产婴儿（孕24至36周出生）的数据与足月儿（孕37周或更久出生）的数据分别进行分析。
共有122,754名妇女和青少年在孕24至43周分娩了无畸形的单胎活婴。在分析的12,317名早产婴儿中，发病率和死亡率升高并无特定的出生体重百分位数。然而，在82,361名足月儿且出生体重处于或低于第75百分位数的婴儿中，新生儿死亡率从参考组（体重第26至75百分位数）的0.03%增至出生体重处于或低于第3百分位数婴儿的0.3%（P<0.001）。出生体重处于或低于第3百分位数的婴儿，5分钟阿氏评分3分及以下和脐动脉血pH值7.0及以下的发生率约增加一倍（分别为P=0.003和P<0.001）。出生时插管、出生后第一天惊厥和败血症的发生率在出生体重处于或低于第3百分位数的足月儿中也显著增加。在对母亲的种族、产次和婴儿性别进行调整后，这些差异仍然存在。
孕周对应的出生体重处于或低于第3百分位数的足月儿的死亡率和发病率升高。
