In contrast, a retrospective cohort study by Fernández-Alba et al. [39] in 2017 containing 328 pregnant patients with IUGR and protein S deficiency treated with low molecular weight heparin and 11,884 patients in the control group, found no significant association between protein S deficiency and IUGR, the prevalence of IUGR in the protein S deficiency being 2.7%, while in the control group was 4.1%, the OR was 0.66, with 95% CI 0.34–1.28. The gene discussed is PROS1; the disease is hereditary thrombophilia due to congenital protein S deficiency.