Pregnant Wistar rats received a therapeutic dose (0.72 mg/kg body weight) of intramuscular sulfadoxine-pyrimethamine on days 5, 12, and 19 of gestation. The treated animals showed elevated neutrophilic lobe average and increased urinary excretion of formiminoglutamic acid (FIGLU) as compared with controls (p < 0.001), confirming folic acid deficiency due to sulfadoxine-pyrimethamine treatment. Complete embryo resorption occurred in the treatment group, while the control animals littered normally. These findings imply that sulfadoxine-pyrimethamine should be used with utmost caution in early pregnancy as this regimen can lead to folic acid deficiency and consequent pregnancy wastage.