Showstack J A, Budetti P P, Minkler D
Am J Public Health. 1984 Sep;74(9):1003-8. doi: 10.2105/ajph.74.9.1003.
To assess the association with birthweight of prenatal medical care, length of gestation, and other prenatal factors, birth certificate data were studied for babies born in 1978 to mothers who were residents of Alameda or Contra Costa counties, California. Using multiple regression data analytic techniques, adequate prenatal care (defined by the number of prenatal care visits compared to length of gestation and month of start of care) was found to be associated with an increase of 197 grams in average birthweight. This effect was even greater for Black infants and infants of short length of gestation. Adding length of gestation to the equation increased significantly the proportion of the variance in birthweight accounted for. For babies of short gestation (less than or equal to 280 days), the addition of length of gestation was associated with a halving of the association of prenatal care with birthweight. The results suggest that researchers need to take into account the nonlinear relationship between length of gestation and birthweight when assessing factors that affect birthweight.
为评估产前医疗护理、妊娠期长度及其他产前因素与出生体重之间的关联，对1978年在加利福尼亚州阿拉米达县或康特拉科斯塔县居住的母亲所生婴儿的出生证明数据进行了研究。运用多元回归数据分析技术发现，充分的产前护理（根据产前护理就诊次数与妊娠期长度及护理开始月份进行定义）与平均出生体重增加197克相关。这种影响在黑人婴儿和妊娠期短的婴儿中更为明显。将妊娠期长度纳入方程后，出生体重方差的解释比例显著增加。对于妊娠期短（小于或等于280天）的婴儿，增加妊娠期长度会使产前护理与出生体重之间的关联减半。结果表明，研究人员在评估影响出生体重的因素时需要考虑妊娠期长度与出生体重之间的非线性关系。
