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Here is the abstract for a recent study that found that use of a prenatal vitamin in the first trimester of pregnancy substantially reduced the risk for development of pre-eclampsia, especially in "overweight" and "obese" women.
The most intriguing finding of the study was that taking a prenatal vitamin in the first trimester lowered the risk for pre-eclampsia by 55% in "overweight" women, and by 62% in "obese" women.
Surprisingly, only about 1/3 of women of any size in this study actually took a prenatal vitamin during the first trimester. Other studies of relatively affluent first-world countries show that only about 30-60% of women routinely took prenatal vitamins before or in the first trimester. This is why improving prenatal vitamin use is a public health intervention which could have significant potential impact.
This may be especially true in obese women, since women of size tend to have lower rates of prenatal or preconception supplement use (45% vs. 60% in one study).
The $64,000 question is whether we can lower pregnancy complication rates in obese women by encouraging them to routinely take prenatal vitamins, even when not actively trying to get pregnant.
Caveats to the Study
The findings of this study are intriguing and deserve to be followed up. However, keep in mind that this is a relatively small study and that these results need to be duplicated multiple times before a true correlation can be established.
Also keep in mind that other studies on prenatal vitamin use (multiple or single vitamins) in the overall population have found more ambivalent results or even poorer outcomes with routine supplementation.
So it's important not to over-interpret this one study or make broad policy recommendations based on it.
Still, it was significant that prenatal vitamin use made such a difference in women of size in this study. Why might this be?
Research suggests that many women of size have nutrient deficiencies such as low vitamin D, and some research suggests that low levels of vitamin D or other nutrients may be associated with higher risk for pre-eclampsia, so this could be explain why prenatal vitamin use was so helpful. However, not all research supports such an association, so again, caution is needed.
It might be that supplementation is most beneficial only for those with significant nutrient deficits. A more sensible policy might be routine pre-conception nutrient testing for those most at risk rather than routine supplementation across the board for everyone.
Since obese women are at significant risk for pre-eclampsia and certain birth defects, pre-conception nutrient testing is something that women of size who are considering pregnancy might want to consider.
Personally, I favor pre-conception testing and emphasizing the use of whole foods and excellent nutrition as the best approach to lowering the risk for complications in women of size.
To me, the best approach is always to emphasize nutrition before pills. I think artificial pills only go so far in helping nutrient deficiencies, and vitamin supplements of one or two particular vitamins can sometimes induce imbalances of other vitamins or minerals. Frankly, focusing on increasing dietary intake of fruits and vegetables may be the safest way to improve nutritional status and decrease risks before and during pregnancy.
Still, there is a place for vitamins and/or medications at times. A prenatal vitamin before pregnancy and during the first trimester might be helpful for many people. It seems like a common-sense public health strategy that might help and is at minimal risk for harm if it's done in moderation.
But the bottom line is that we need more studies showing the effect of routine prenatal vitamin use in subgroups such as overweight and obese women. I would particularly like to see research stratified by class of obesity, nutritional intake, pre-conception nutrient status, and insulin resistance status so we could have a more nuanced examination of potential confounders as well.
Only when such nuanced research is done will we truly know for sure whether routine pre-conception and prenatal vitamin supplementation is an effective strategy for lowering the risk of complications in women of size.
Reference
The use of pregnancy-specific multivitamin supplements is widely recommended to support maternal homeostasis during pregnancy. Our objective was to investigate whether multivitamin use during pregnancy is associated with a reduced risk of pre-eclampsia.
The effect of multivitamin use on incidence of pre-eclampsia in lean and overweight/obese women was analysed using data collected between 2006 and 2011 as part of the Environments for Healthy Living Project, Griffith University, Australia. A total of 2261 pregnancies were included in the analysis with pre-eclampsia reported in 1.95% of subjects.
Body mass index (BMI) ≥ 25 was associated with a 1.97-fold [95% confidence interval (CI): 0.93, 4.16] increase in pre-eclampsia risk. First trimester multivitamin use was reported by 31.8% of women and after adjustment, was associated with a 67% reduction in pre-eclampsia risk (95%CI: 0.14, 0.75).
Stratification by BMI demonstrated a 55% reduction in pre-eclampsia risk (95%CI: 0.30, 0.86) in overweight (BMI: 25-29.9) and 62% risk reduction (95%CI: 0.16, 0.92) in obese (BMI: ≥30) cohorts that supplemented with multivitamins in the first trimester of pregnancy. This finding may be particular to the Australian population and reflect inherent nutritional deficits.
First trimester folate supplementation was found to reduce pre-eclampsia incidence [adjusted odds ratios (AOR) 0.42 95%CI: 0.13, 0.98] and demonstrated significance upon stratification by overweight status for women with BMI >25 (AOR 0.55 95%CI: 0.31, 0.96). These results support the hypothesis that multivitamin supplementation may be beneficial in reducing the incidence of pre-eclampsia during pregnancy and be of particular importance for those with a BMI ≥25.
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