Background: Ninety nine percent of maternal mortality is from developing countries with an important contribution of the adolescents. Preeclampsia is the main cause of maternal mortality and low birth weight in developing countries with at least sixty percent of the contribution of the extreme maternal morbidity. Various preventive protocols for preeclampsia have been suggested one is the combination of calcium with conjugated linoleic acid (calcium-CLA). This protocol has been studied since 1992 in developing countries. Objective: To estimate in primigravidas the protective effect of calcium supplementation (600 mg/day/elemental) combined with conjugated linoleic acid (450 mg/day) from 12-16 weeks of gestational age to birth with respect to preeclampsia development. Methods. Six studies were reviewed, an open poulation trial, four randomized controlled trials and a case-control study nested in a cohort. The above studies included primigravid patients as inclusion criteria and were performed in three developing countries. The outcome was preeclampsia (pregnancy-induced hypertension with significant proteinuria (> 300 mg/24 hours). The typical odds ratio was calculated for the randomized clinical trials. The incidence of preeclampsia was evaluated in three different age groups (13-18 years old,19-34 years old, and 35-45 years old). Results: 3.028 primigravidas were analyzed. The four randomized clinical trial compared calcium-CLA against placebo and observed a typical OR of 0.20 (95% CI 0.05-0.82) (p< 0.05). The last study a case-control study nested in a cohort performed during the last four years evaluated the preventive effect of calcium suplementation in primigravid patients (OR = 0.96, 95%CI: 0.73 – 1.27) (p = 0.82) and was compared with the preventive effect of calcium-CLA supplementation (OR = 0.00, 95%CI: 0.00 – 0.44) (p = 0.005). Conclusion: In developing countries the supplementation of calcium-CLA reduced preeclampsia risk in comparison with placebo, this supplementation in comparison with calcium alone observed a total preventive effect in the adolescent group. Is neccesary evaluate this preventive protocol in developed countries.