Objectives: Our objective was to identify statistically significant variables that determine the length of human gestation.
Study design: Multiple linear regression was used to analyze 9355 observations from the Delivery Interview Program, a cross-sectional study conducted from 1977 through 1980 at the Boston Hospital for Women (now called the Brigham and Women's Hospital).
Results: Maternal parity, age, and race were found to be the most important variables determining the length of human gestation. Multiparous women, women aged < 19 or > 34 years, and black women were found to have shorter gestations than primiparous women, women aged 19 to 34 years, or white women.
Conclusion: By means of our linear model the length of pregnancy for women with different risk factors can be estimated more precisely than Naegele's rule allows.