As long as you don’t overdo it, yes. The United States daily requirements for magnesium are actually increased in pregnant women as follows:
Adult Female: 300mg
Pregnant Female: 320mg
Breastfeeding Female: 350mg
That’s too little according to many sources. The Baby Center goes even farther:
Pregnant women, 19 to 30 years of age: 350 milligrams (mg) of magnesium per day
Pregnant, 18 and younger: 400 mg
Pregnant, 31 and older: 360 mg
Breastfeeding women, 19 to 30: 310 mg
Breastfeeding, 18 and younger: 360 mg
Breastfeeding, 31 and older: 320 mg
There is some evidence that magnesium helps prevent the uterus from contracting too soon, though this is still inconclusive. Magnesium certainly helps prevent cramps, though.
Magnesium citrate, on the other hand, is something that the FDA recommends taking only when the benefits outweigh the risks.
In BJOG: An International Journal of Obstetrics and Gynaecology in August 2007, two studies are cited. The first study concluded:
“Additional magnesium appeared to benefit the fetus during labour. Significantly fewer showed fetal heart rate irregularities, meconium-stained liquor and partogram abnormalities. The supplemented group also had fewer late stillbirths either before or during labour.”
“It must be stressed that these secondary findings, although of interest, need to be substantiated by further work. Until then, supplementation cannot be recommended but poorly nourished women should be encouraged to eat a diet that contains adequate magnesium, in particular brown – rather than white – bread.”
The second study had the following comments:
“In our commentary, we recommend further research to find out whether improving calcium intake from before pregnancy might reduce not only blood pressure, but associated problems such as protein in the urine as well. We suggest that fortification of staple foods might make the benefits of adequate calcium intake available to all pregnant women, not only those with access to antenatal care.”
“While these studies show that the consumption of certain minerals during pregnancy results in favourable outcomes for mother or baby, it must be stressed that in these studies, the intake of supplements are carefully measured.”
“Women should attend their antenatal clinics so that tests identifying problems can be carried out. If they are interested to know more about supplementation, they should speak to their GPs and midwives for further advice.”
“We should note that women who do not have a deficiency in magnesium or calcium need to be careful about taking extra supplements if they don’t need it.”
So, while magnesium looked like a plus, these were undernourished women in the study. Assuming you have a healthy diet, you may want to think twice about using magnesium supplements.
There are several other studies, and while most suggest that magnesium is beneficial for the fetus, almost all balance that by saying that the results for well-nourished women may be different.
So What to Do?
In light of the research, try eating better. An extra serving of spinach, nuts or halibut each day may do wonders. If you really feel the need to take supplements, at least try to make sure the dosage is not much over the RDA of 350mg.