Effects of maternal and paternal age on Caucasian and Native American preterm births and birth weights.

The purpose of this study was to compare the effects of maternal and paternal age on Native American and Caucasian infants. Data were abstracted from birth records compiled in North Dakota from 1978 to 1992. Native Americans had a 45% higher risk for preterm births, a 140% higher risk for low birth weight (LBW) (<2500 g), and a 131% higher risk for very LBW (<1500 g) compared with Caucasians. Maternal and paternal age both had a "U-shaped" effect on preterm birth. However, while the risk for preterm birth was increased for both teenage mothers and fathers, the risk was also significantly increased only for mothers between the ages of 36-40 and 41-45. There was also a "U-shaped" relationship between LBW and parental age, and again the risk was statistically significant for different age groups. For mothers, the risk was decreased significantly for those 26 to 30 years of age, whereas for fathers, it was increased significantly for those <20 years of age. There was also a significant interaction between paternal age and race, with teenage Native American fathers having a slight (4%), but statistically significant, increased risk for having LBW children compared with teenage Caucasian fathers. The relationship between parental age and very LBW was also "U-shaped," but while the odds ratios for each maternal age group were significant, none of the odds ratios for any of the paternal age groups was statistically significant. The influence of teenage fathers on preterm and LBWs has not been previously reported, and the finding that paternal age has a greater influence among Native Americans is especially intriguing and deserving of further investigation.