Micronutrient Supplementation in Pregnancy: How much rational?

Micronutrient Supplementation in Pregnancy: How much rational?

Introduction:

                It is strange but true that in many aspects of clinical practice, the decision-making on prescribing a drug is based on the information provided by pharmaceutical companies and their representatives who are ubiquitously surrounding us. Micro-nutrient supplementation in pregnancy is one such aspect where many a times, the pharmaceutical companies have a tendency to overhype an agent. Their overhype tends to get potentiated by our laziness in keeping our information updated. Ultimately this brings us dangerously close to being irrational in prescribing these agents. The purpose of this write-up is to make one sensitive to the current evidence based thinking in prescribing different micronutrient in clinical practice of obstetrics.

Vitamin A supplementation during pregnancy:

                Background: The World Health Organization recommends routine vitamin A  supplementation during pregnancy or lactation in areas with endemic vitamin A deficiency (where night blindness occurs), based on the expectation that supplementation will improve maternal and newborn outcomes including mortality, morbidity and prevention of anemia or infection.  

                Review: However for studying how rational this recommendation is, 88 reports of 31 trials, published between 1931 and 2010, were examined for review. The pooled results of two large trials in Nepal and Ghana (with almost 95,000 women) do not currently suggest a role for antenatal vitamin A supplementation to reduce maternal or perinatal mortality. However the populations studied was probably different with regard to baseline vitamin A status and there were problems with follow-up of women.

                Result: There is good evidence that antenatal vitamin A supplementation reduces maternal anemia for women who live in areas where vitamin A deficiency is common or who are HIV-positive. In addition the available evidence suggests a reduction in maternal infection, but these data are not of a high quality.

Magnesium supplementation in pregnancy:

                Background: Many women, especially those from disadvantaged backgrounds, have intakes of magnesium below recommended levels. Magnesium supplementation during pregnancy may be able to reduce fetal growth retardation and pre-eclampsia, and increase birth weight.

                Review: Seven trials involving 2689 women were included.

                Result: There is not enough high quality evidence to show that dietary magnesium supplementation during pregnancy is beneficial.

Vitamin C supplementation in pregnancy

                Background: Vitamin C supplementation may help reduce the risk of pregnancy complications like pre-eclampsia, intrauterine growth restriction and maternal anemia. There is a need to evaluate the efficacy and safety of vitamin C supplementation in pregnancy.

                Result: The data are too few to say if vitamin C supplementation either alone or in combination with other supplements is beneficial during pregnancy. Preterm birth may have been increased with vitamin C supplementation.

Vitamin E supplementation in pregnancy

                Background: Vitamin E supplementation may help reduce the risk of pregnancy complications involving oxidative stress, such as pre-eclampsia. There is a need to evaluate the efficacy and safety of vitamin E supplementation in pregnancy.

Result: The data are too few to say if vitamin E supplementation either alone or in combination with other supplements is beneficial during pregnancy.

Pyridoxine (vitamin B6) supplementation in pregnancy

                Background: Vitamin B6 plays vital roles in numerous metabolic processes in the human body, such as nervous system development and functioning. It has been associated with some benefits in non-randomized studies, such as higher Apgar scores, higher birth weights, and reduced incidence of pre-eclampsia and preterm birth. Recent studies also suggest a protection against certain congenital malformations.

                Conclusions: There were few trials, reporting few clinical outcomes and mostly with unclear trial methodology and inadequate follow up. There is not enough evidence to detect clinical benefits of vitamin B6 supplementation in pregnancy and/or labour other than one trial suggesting protection against dental decay. Future trials assessing this and other outcomes such as orofacial clefts, cardiovascular malformations, neurological development, preterm birth, pre-eclampsia and adverse events are required.

Marine oil, and other prostaglandin precursor, supplementation for pregnancy uncomplicated by preeclampsia or intrauterine growth restriction

                Background: Population studies have shown that higher intakes of marine foods during pregnancy are associated with longer gestations, higher infant birth weights and a low incidence of pre-eclampsia. It is suggested that the fatty acids of marine foods may be the underlying cause of these associations.

Results: There is not enough evidence to support the routine use of marine oil, or other prostaglandin precursor, supplements during pregnancy to reduce the risk of pre-eclampsia, preterm birth, low birth weight or small-for-gestational age.

Selenium in pregnancy:

•       Although pregnant women have a higher need for selenium, they usually get enough of this mineral through dietary means, and supplementation is not usually necessary. In fact, consuming too much can cause serious problems, such as selenium toxicity or even death.

Multiple-micronutrient supplementation for women during pregnancy

Review: Nine trials (15,378 women) are included

Results: The evidence provided in this review is insufficient to suggest replacement of iron and folate supplementation with a multiple-micronutrient supplement. A reduction in the number of low birth weight and small-for-gestational-age babies and maternal anemia has been found with a multiple-micronutrient supplement against supplementation with two or less micronutrients or none or a placebo, but analyses revealed no added benefit of multiple-micronutrient supplements compared with iron folic acid supplementation. These results are limited by the small number of studies available. There is also insufficient evidence to identify adverse effects and to say that excess multiple-micronutrient supplementation during pregnancy is harmful to the mother or the fetus.

Conclusion:  Further research is needed to find out the beneficial maternal or fetal effects and to assess the risk of excess supplementation and potential adverse interactions between the micronutrients.

Practice Points:

It is obvious that in clinical practice many pharmacological agents flood the markets regularly with pressure on clinicians to prescribe them. Many a times these products are introduced and promoted with great rigor and with seemingly magical promises. However, a sound scientific evaluation of these can help the clinician to take an accurate and rational decision in prescribing them.