Problem The renin-angiotensin system is associated with angiogenesis, tissue remodeling, prenatal development, and Th2 cytokine production. The purpose of this study was to evaluate whether polymorphisms in angiotensin I-converting enzyme [ACE insertion/deletion (I/D)], angiotensinogen (AGT M235T), and angiotensin II type 1 receptor (AT1R 1166A>C) affect the prevalence of spontaneously aborted fetuses (SAFs). Method of study One hundred and ninety-eight SAFs wereC genotypes. Results II/MM/AA, II/MT/AA, and II/TT/AC of ACE/AGT/AT1R were significantly different from controls. In particular, the statistical significance of the II/MM/AA genotype remained strong in chromosomally normal SAFs. Conclusion Our data suggest that the II/MM/AA of ACE/AGT/AT1R is a possible predisposing factor for spontaneous abortion.