2 thrombophilias and recurrent pregnancy loss is almost unknown in triethnic populations such as the Colombian population whose genetic mixture is approximately 70% Caucasian, 15% Amerindian, and 15% African [23, 24]. We conducted this study to evaluate the association between inherited thrombophilia and recurrent pregnancy loss in a group of patients from Colombia. 2. Patients and Methods 2.1. Study Population. An unmatched case-control study was conducted on 93 patients and 206 healthy women from a province in Northwest Colombia (Antioquia) chosen for convenience. The inclusion criteria for the patient group were a history for recurrent pregnancy loss (three or more miscarriages) and any of the following vascular pregnancy manifestations: one or more second-trimester or later loss- es, severe or recurrent preeclampsia, intrauterine growth restriction, placental abruption, or otherwise unexplained intrauterine death. The women with recurrent pregnancy loss were selected among more than 3000 patients who had consulted, over the last 20 years, to the Reproduction Group at Universidad de Antioquia in Medell´ın, Colombia. The control group included 206 healthy women with a history of two or more normal pregnancies, no more than one miscarriage, and no history of any of the criteria for inclusion in the patient group. The sample size estimated for a type I error of 5% and a power of 80% was 300 subjects (2 : 1 ratio between controls and cases). This estimation was based on the following average ratios of SNPs in healthy European populations and their odds ratio for recurrent pregnancy loss: 4.3% of heterozygous FV Leiden with an odds ratio (OR) of 4 [8, 25, 26]; 3% of FII G20210A with OR of 3.7 [8, 26]; 9% of MTHFR C677T with an OR of 3.1 [26– 28]. European populations were selected as reference because insuﬃcient information was available about the frequency of inherited thrombophilia in a population with mixed genetic ancestry such as the Colombian. Additionally, deﬁciencies of AT, PC, and PS were determined in an exploratory manner, as a pilot study, since the sample size was not powered to discriminate diﬀerences between patients and controls. This study was approved by the Ethics Committee of the Medical Research Center at the Universidad de Antioquia and all subjects provided informed consent. 2.2. Thrombophilia Screening. Blood samples were drawn from women who were not taking any anticoagulant drugs and who were at least 3 months past the last obstetric event to prevent changes in the APC resistance status and plasma levels of coagulation proteins. Thrombophilia-associated SNPs were genotyped using the methods described by Ridker et al. [29] (FV Leiden), Poort et al. [30] (FII G20210A), and Mandel et al. [31] (MTHFR C677T). The APC resistance status was determined in plasma using a second-generation functional assay based on activated partial thromboplastin time with factor-V- deﬁcient plasma (Test APC RESISTANCE V, Instrumenta- tion Laboratory, Lexington, MA, USA) considering a positive Table 1: Characteristics of patients and controls. Characteristics Age, mean ± SD (years) Age, range (years) Number of previous pregnancies, mean ± SD Number of pregnancy losses, mean ± SD Family history of venous thrombosis (%) Medical history of venous thrombosis (%) History of severe or recurrent preeclampsia (%) History of pregnancies with intrauterine growth restriction (%) History of placental abruption (%) SD: standard deviation; n: number of women Thrombosis Cases Controls (n = 93) (n = 206) 34.1 ± 0.9 41.6 ± 0.7 18–79 23–83 4.4 ± 1.9 3.8 ± 1.4 25.8 6.5 13.0 1,9 0.9 2.8 ± 1.3 0.1 ± 0.3 29 0 0 0 0 APC resistance when the ratio a/b was lower than 2 being (a) in the presence, and (b) in the absence of activated PC. The activities of AT, PC, and PS were determined with com- mercial kits (IL Test Antithrombin, IL Test ProClot, and IL Test Protein S, resp.; Instrumentation Laboratory, Lexington, MA, USA). These proteins were considered deﬁcient when their activity was <50% of their normal functionality. 2.3. Statistical Analysis. The sample size was calculated using the software taman˜o de la muestra (versi o´n 1.1) [32]. The allele and genotype frequencies were compared between patients and controls with a Mantel and Haenzel’s chi-square test and one-tail analysis using SPSS 15.0 [33]. The ORs were calculated with 95% Cornﬁeld’s conﬁdence intervals (CIs) using Epi 6 Stat Calc [34]. 3. Results Demographics of the women from the case and the control groups are shown in Table 1. In 93 cases and 206 controls, the frequency of thrombophilia-associated SNPs (as shown in Table 2) for both FV Leiden and FII G20210A heterozygous carriers was one patient and one control (1.1% versus 0.5%, resp.; OR 2.25; 95% CI, 0–83). Homozygous carriers of the MTHFR 677T allele were detected in 12 patients and 30 controls (12.9% versus 14.9%, resp.; OR 0.85; 95% CI, 0.4– 1.8). APC resistance was found in 5 of 87 patients versus 8 of 187 controls (5.7% versus 4.3%, resp.; OR 1.36; 95% CI, 0.4– 4.8) of which only one women in each group was attributable to FV Leiden. Additionally, none of the patients and only two of the controls had <50% AT activity (0 versus 1%, resp.; OR 0; 95%, CI 0–9.2), and 2 of 91 patients versus 3 of 195 controls showed <50% in PC activity (2.2 versus 1.5%, resp.; OR 1.44; 95% CI, 0.2–10.8), as shown in Table 3. Since the determinations of PS levels were nonreproducible in stored samples, these measurements were excluded from analysis in this study. No association was observed between recurrent pregnancy loss and inherited thrombophilia by either SNP genotypes (FV Leiden, FII G20210A, and MTHFR C677T) or