Currently, there are no direct and reliable methods to measure the body fat content of women during pregnancy. Estimates of fat accretion can significantly affect calculations of energy requirements. We report here the first direct measurement of determining the body fat content of two women during pregnancy using the Fourier transform near-infrared spectroscopy (FT-NIR) method. Fourier transform near-infrared spectroscopy was shown to provide comparable results to dual-energy X-ray absorptiometry and magnetic resonance imaging. These latter methods, even though very reliable to measure body fat levels, cannot be used to measure the body fat of women during pregnancy because of health concerns, while FT-NIR poses no health risk. The FT-NIR results showed the percent body fat remained relatively constant throughout pregnancy, but fat mass and fat free mass increased. Fat mass followed an S curve with a maximum increase between 15 to 25 weeks of gestation that was only detected by repeated measurements using the FT-NIR technique. These results demonstrate the value of the FT-NIR method to directly measure the fat content of pregnant women in minutes instead of relying on indirect calculations or taking measurements before and after pregnancy to track gestational fat mass accretion.