Preterm Labor and Magnesium
I was first introduced to magnesium during my obstetrical training, where I saw how effective magnesium sulfate was in preventing seizures and restoring normal blood pressure in pregnant women suffering from toxemia. Magnesium is also frequently given to women having preterm labor to stop contractions. It works!
A good friend of mine, Alexa, had her third baby in 1994. About seven weeks before the baby was due, she started to have contractions that would only stop when she lay down. Because she was 2.5 centimeters dilated and almost fully effaced (conditions often present when a woman goes into labor with a full-term third child), she was put on bed rest. Luckily this helped, and she was able to avoid a lengthy stay at the hospital. After having her baby, Alexa was extremely run down, had frequent migraines, and severe muscle cramps. She decided to go to a Naturopath for help. He immediately diagnosed severe magnesium deficiency, and she was given weekly magnesium IVs to correct the imbalance.
Alexa’s magnesium deficiency isn’t all that unusual. In fact, the National Academy of Sciences found (in 1997) that most Americans were deficient in magnesium.  The following factors contribute to this:
Food processing removes much of the magnesium that’s naturally found in certain foods.
Taking antacids (and some other medicines for indigestion) disrupts magnesium absorption.
Magnesium and other minerals are depleted by modern farming practices.
Medications including common diuretics, birth control pills, insulin, tetracycline and other antibiotics, and cortisone cause the body to waste magnesium.
Alexa’s OB/GYN was insistent that she get 1500 mgs of calcium every day to protect her baby’s and her bones. He told her to take a couple of Tums, an antacid, any day she didn’t get enough calcium from the food she ate. Tums contains calcium, and it was the calcium “supplement” he recommended to all his patients. (This was his strategy for keeping her calories from dairy fat down, too.) He never recommended that she increase her magnesium, just her calcium. It’s not surprising that she had a magnesium deficiency after following his advice during three pregnancies.
Christiane Northrup, MD
Board-certified ob/gyn, bestselling author
 Institute of Medicine, Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (Washington, DC: National Academy Press, 1997).