Aims Toxoplasma infection in pregnancy is usually treated with long-term administration of the macrolide spiramycin to prevent fetal malformations. We had empirically observed that treated patients seldom developed pregnancy-induced hypertension (PIH), a common and severe disorder of pregnancy whose aetiology and pathogenesis are still debated. Some clinical and experimental data suggest that infection could play a role in its development. Methods To test this hypothesis, we studied a cohort of 417 pregnant women treated with spiramycin because of seroconversion for Toxoplasma gondii and 353 low-risk women who did not take any antibiotic during pregnancy. PIH was defined as blood pressure >140/90 mmHg on two or more occasions, occurring after 20 weeks of gestational age. Results Seventeen (5.2%) women in the control group developed PIH compared with two (0.5%) in the case group. The odds of developing the disease were significantly lower in the treated subjects (odds ratio = 0.092, 95% confidence interval 0.021, 0.399; P