Relationship between blood pressure, calcium consumption, and urinary calcium excretion in pregnant adolescents

Background: Pregnancy-induced hypertension (PIH) occurs more frequently among poor primigravidas, and recent studies have suggested that PIH is associated with a reduced calcium intake and urinary calcium excretion. Patients and methods: To evaluate this association 56 Brazilian primigravida adolescents of low socioeconomic conditions were studied during the whole gestational period. PIH occurred in 18% of the patients. The age of normal pregnant teenagers (NP) and hypertensive pregnant adolescents (HT) was 16.0 +/- 0.2 and 15.8 +/- 0.6 years, respectively. Results: Intake of calories, protein, fat, carbohydrate, sodium, potassium, iron, and phosphorus were similar in NP and HT being of 3026 +/- 128 vs 2965 +/- 208 (kcal/day); 109 +/- 3.9 vs 102 +/- 12 (g/day); 84 +/- 5 vs 81 +/- 8 (g/day); 488 +/- 24 vs 474 +/- 37 (g/day); 3898 +/- 268 vs 3383 +/- 452 (mg/day); 3284 +/- 140 vs 3276 +/- 364 (mg/day); 21 +/- 1 vs 20 +/- 2 (mg/day); and 1110 +/- 59 vs 1068 +/-. 94 (mg/day), respectively. However, there was a significant difference in dietary calcium intake between NP (886 +/- 69 mg/day) vs HT (635 +/- 63 mg/day, p = 0.05), and a significant reduction in the urinary calcium/creatinine ratio in HT when compared to NP: 0.20 +/- 0.04 vs 0.35 +/- 0.03 mmol/mmol (p = 0.02). There was an inverse and significant correlation between dietary calcium intake and systolic BP (r = -0.28 and p = 0.05). The urinary calcium/creatinine ratio was significant and negatively correlated with diastolic BP (r = -0.26 and p = 0.05). Conclusion: We conclude that a low intake of calcium may be involved in the development of gestational hypertension.