Purpose: To compare and confirm the impact of prepregnancy body mass index on pregnancy outcome in women with a singleton conceived by assisted reproductive technology and spontaneously conceived pregnancy. Methods: A sample of 165 and 247 pregnant women with and without assisted reproductive technology were retrospectively recruited from electronic medical charts of C hospital. Results: There were significant differences between the two groups for maternal age, paternal age, length of marriage, prepregnancy body mass index, parity, spontaneous abortion experience, and preterm delivery. A prepregnancy body mass index of ${geq}25$ was associated with higher risk for maternal and neonatal complication in the assisted reproductive technology group. Conclusion: The results indicate that a higher prepregnancy body mass index is associated with increased risks for adverse pregnancy outcomes for women using assisted reproductive technology. So these women need appropriate care to compensate for the risk.