Abstract: The present invention provides a method for determining the gender of a fetus by assaying the sex hormones, evaluating the overall reducing/oxidizing (redox) activity, and/or evaluating the radical scavenging capacity of the maternal urine or other body fluid. The method can be used to determine fetal gender at any time point during pregnancy. The methods of the present invention also provide for a means for pre-conception offspring gender planning by assaying the sex hormones in urine samples, evaluating the overall reducing/oxidizing (redox) activity, and/or evaluating the radical scavenging capacity of the urine or other body fluid from a non-pregnant female. In some embodiments, the methods described herein are used to sort sperm based on an overall reducing/oxidizing environment of follicular fluids, which can then be used for intrauterine insemination.