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Calcium Supplements May Save Mothers and Babies Worldwide
By Marcia J. Egles, MD, abstracted from ”World Health Organization randomized trial of calcium supplementation among low calcium intake pregnant women” in the March 2006 issue of the American Journal of Obstetrics and Gynecology
The World Health Organization (WHO) has published the results of a major, worldwide study which concludes that calcium supplementation during pregnancy is associated with a significant reduction in eclampsia, severe high blood pressure, pre-term delivery, and death of the newborn.1  Eclampsia, also known as toxemia with seizures, is the occurrence of seizures not attributable to another cause during pregnancy.  Eclampsia, if untreated, may be fatal to both the mother and baby.  Eclampsia develops in 1 of 200 women with pre-eclampsia.  Pre-eclampsia is a serious condition marked by high blood pressure, abnormal swelling, and protein passed into the urine.(2, 3) The exact cause of pre-eclampsia and eclampsia is not known.  Pre-eclampsia occurs in about 5% of pregnancies.  Worldwide, eclampsia is estimated to cause 50,000 deaths annually.4
A multi-centered, randomized, placebo-controlled, double–blind trial was performed at prenatal care clinics serving populations with high occurrences of low calcium intake.   Results from seven centers in Argentina, Egypt, India, Peru, South Africa, Viet Nam, and England were included with a total of 8325 women.   As determined by dietary interviews, random samples of the women had intakes of calcium of less than 600mg per day, which is about half the amount recommended during pregnancy.  All of the participants were first-time expectant mothers less than 20 weeks into their pregnancies.  They were generally healthy, without high blood pressure or heart, kidney or seizure disorders. The women were randomly divided into two groups.  The groups had similar demographics and similar compliance throughout the study.
One group of women, the treatment group, received 500 mg of chewable calcium carbonate three times daily (1.5 g per day) for the remainder of their pregnancies.  The control group received calcium-free placebo tablets.   The study was double-blind, which means that neither the women themselves nor the caregivers knew to which group a given woman belonged. The women were followed at their prenatal visits and given monthly allotments of tablets.  Compliance was assessed by counting any untaken tablets remaining in the bottles returned at the end of each month.. The women received usual prenatal care including blood pressure and urine protein checks. Iron and folate were the only other supplements used, and acetaminophen (Tylenol) and non-calcium antacids were allowed.
The primary purpose of the study was to determine whether calcium supplementation of pregnant women with low calcium intake reduces pre-eclampsia and pre-term delivery.  The reduction of pre-eclampsia in the calcium treatment group was not statistically significant. However, significant reductions were noted in pre-term (less than 37 weeks) delivery and early pre-term (less than 32 weeks) delivery, particularly among women who were less than twenty years old.   For 1400 mothers who were under twenty years old in the calcium group, there were 34 deliveries prior to the 32nd week.  For 1404 mothers in the matched under twenty placebo group, there were 53 early pre-term deliveries. The study also reported significant reductions in the severe complication of eclampsia (17 of 4151 women in the calcium group vs. 25 of 4161 in the placebo group). Although overall high blood pressure was not significantly lessened, severe high blood pressure was reduced.  Overall, an index of other severe maternal events including placental abruption, HELLP (hemolysis, elevated liver enzymes, and low platelets) syndrome, renal failure, or death was reduced.  Neonatal deaths (37 deaths in 3953 births in the calcium group vs. 53 deaths in 3956 births in the placebo group) were similarly less.
The study considered the degree to which maternal/infant health could be improved by adequate calcium intake.  The authors calculate that for every 125 pregnant women supplemented, one severe outcome would be avoided.   One infant death could be prevented for every 250 pregnant women treated in populations with low calcium intakes.1
The protective effects of calcium supplementation in women with low calcium intakes has been observed in smaller reviews.5  This WHO study is a major, randomized study confirming the benefit of calcium supplementation.
1  Villar J et al, World Health Organization randomized trial of calcium supplementation among low calcium intake pregnant women. Am.J.Obstetrics and Gynecology, volume 194, issue 3, March 2006, 639-649
2  “Preeclampsia and Eclampsia” on the Merck Manual Website www.merck.com/mrkshared/mmanual/section18/chapter252/252d.jsp
3  “Eclampsia” on Medline Plus, a service of the U.S. National Library of Medicine
4  “The Must-Read Trial:Eclampsia” on Bandolier  www.jr2.ox.ac.uk/bandolier/band17/b17-5
5  Hofmeyr GJ et al, Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems (Cochrane Review), The Cochrane Library, Issue 1, John Wiley and Sons, Chichester, UK (2005).