Human reproduction is a biological phenomenon, however, sociocultural factors such as marital status influence pregnancy outcome and reproductive success. In the present study the impact of maternal marital status on pregnancy outcome was tested for all births, which had taken place in Austria between 1999 and 2004, which met the following criteria: single births, nulliparity, mothers older than 19 years (n = 179 830). The rate of preterm delivery (< 37 beginning weeks of gestation) and rate of low birth weight (< 2500 g) among term births were significantly higher among unmarried mothers in comparison to married mothers. Additionally the newborns of unmarried mothers were significantly lighter and shorter than those of married mothers. This was especially true of immigrant mothers. No significant differences between married and unmarried mothers were found regarding mode of delivery. Even at the beginning of the 21st century unmarried status represents an important stress factor for pregnant women.