The purpose of this study was to analyze self-reported physical activity during the second trimester of pregnancy and its effect on neonatal outcomes, as one of the major reasons why pregnant women tend to reduce their physical activity is the fear of harming their unborn baby. Neonatal outcomes included into the statistical analysis were low birth weight (2,500 g or less) and Apgar score in the first minute (7 or less). Biological factors affecting neonatal outcomes established by this study were maternal obesity and the number of previous births. On the other hand, no particular physical activities or its volume were found to influence neonatal outcomes. The only observed exception was swimming with favorable effect and cycling whose adverse effect on delivery outcomes requires future research.