Although the physiopathogenesis of preeclampsia remains uncertain, a decrease in prostaglandin (PGE₂) level has been implicated, possibly because of prostaglandin's role in regulating intracellular ionic calcium levels. Supplementation of prostaglandin precursors and calcium could, therefore, prevent preeclampsia by sustaining PGE₂ levels. Herrera and colleagues studied women at high risk of preeclampsia to investigate the effect of linoleic acid and calcium supplementation.

Over 1,600 healthy Colombian primigravid patients between 28 and 32 weeks of gestation were screened to identify those who were at increased risk of preeclampsia. Inclusion criteria for high risk included a biopsychosocial profile score of three or greater, a positive roll-over test and a mean arterial pressure of 85 mm Hg or greater. Exclusion criteria were previous elevations of diastolic blood pressure, drug use or history of cardiovascular or renal disease. After collection of baseline data, 89 patients who met the criteria provided blood samples for laboratory analysis and completed nutritional inventories. The patients were randomly assigned to receive either 450 mg of linoleic acid plus 600 mg of calcium or identical placebo tablets. Patients were instructed to take the medications in the morning, to rest in the left lateral position for at least 30 minutes daily and to avoid taking acetylsalicylic acid and nonsteroidal anti-inflammatory drugs. The patients were monitored every four weeks until 36 weeks of gestation and then twice per week until delivery. Preeclampsia was defined as pregnancy-induced hypertension (repeated measures of 140/90 mm Hg or greater), with proteinuria greater than .003 g per dL (0.3 g per L).

The treated women did not differ from the women in the placebo group in any demographic or obstetric variable. The groups were also comparable in nutritional profiles and in measures of compliance during the study. The incidence of preeclampsia in the treated women was 9.3 percent, significantly lower than the 37.2 percent in the control group. Two patients (4.7 percent) in the treated group and six patients (14 percent) in the control group developed severe preeclamptic toxemia. Treated women had lower mean diastolic blood pressures, longer gestation periods, higher birth weights, fewer low birth weight infants, fewer infants small for gestational age, and a lower rate of cesarean delivery. No side effects attributable to the treatment or placebo were reported.

The authors conclude that daily dietary supplementation with linoleic acid and calcium during the third trimester reduces the incidence of preeclampsia in high-risk patients and contributes to improved pregnancy outcomes.