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Homocysteine and Miscarriage - What You Should Know


Updated June 19, 2014

Homocysteine is a type of amino acid that is naturally found in the body. Homocysteine is not harmful at normal levels, but when levels of homocysteine are too high, health problems can result. Some researchers have found correlations between high homocysteine and risk of miscarriage.

Why High Homocysteine May Cause a Miscarriage:

Elevated homocysteine has not been proven to cause miscarriage; researchers are still investigating the link. If the link is valid, though, the most likely theory is that high homocysteine causes a condition called hypercoagulability, where homocysteine levels are high and the blood clots more easily -- this could mean that tiny blood clots could block blood vessels in the placenta, similar to in antiphospholipid syndrome.

Homocysteine and MTHFR Gene Mutations:

People who have variations in the MTHFR gene, especially the C677T variation, are more likely to have high-homocysteine levels. MTHFR gene variants have been correlated with increased miscarriage risk by some past studies, and the leading theory behind the association is that it is related to high-homocysteine levels in people with MTHFR gene variants.

Some doctors test for MTHFR gene variants as a part of the recurrent miscarriage testing workup, but others feel it is more valuable to test homocysteine instead because not everyone with MTHFR gene variants will have high homocysteine.

Other Reasons for High Homocysteine:

MTHFR gene variants are not the only cause of high homocysteine. The metabolism of homocysteine in the body involves folic acid, vitamin B6 and vitamin B12. People who are deficient in those vitamins can have high-homocysteine levels. In addition, a variety of underlying health conditions and medications may be related to high-homocysteine levels.

Health Risks of High Homocysteine:

Research is conflicted on exactly what role high homocysteine plays in long-term health, but some studies have found that high homocysteine correlates with the risk of developing heart disease and neurological problems.

Treating Elevated Homocysteine:

In the context of recurrent miscarriages, there are no formal recommendations to check homocysteine and no universally recommended treatment protocol for handling elevated homocysteine levels. The association between homocysteine and miscarriages has not been fully fleshed out by research at this time.

Some doctors, however, do test homocysteine (or MTHFR gene variants) and recommend treatment even in the absence of formal recommendations. The usual recommendation in this case is that women with elevated homocysteine levels should take high doses of folic acid and B vitamins in an attempt to normalize the homocysteine level, because folic acid and B vitamins can improve metabolism of homocysteine.

A few doctors may recommend anticlotting therapy, such as heparin or low-dose aspirin, in order to prevent blood clots from forming during pregnancy, but this practice is not standard.


American Academy of Family Physicians, "Homocysteine." familydoctor.org Apr 2006. Accessed 3 Apr 2008

Nelen, Willianne L.D.M., Henk J. Blom, Chris M.G. Thomas, Eric A.P. Steegers, Godfried H.J. Boers, and Tom K.A.B. Eskes, "Methylenetetrahydrofolate Reductase Polymorphism Affects the Change in Homocysteine and Folate Concentrations Resulting from Low Dose Folic Acid Supplementation in Women with Unexplained Recurrent Miscarriages." Journal of Nutrition March 1998. Accessed 3 Apr 2008.

Unfried, Gertrud, Andrea Griesmacher, Wolfgang Weismuller, Fritz Nagele, Johannes C. Huber, and Clemens Tempfer, "The C677T Polymorphism of the Methylenetetrahydrofolate Reductase Gene and Idiopathic Recurrent Miscarriage." Obstetrics & Gynecology 2002. Accessed 3 Apr 2008.

Vollset, Stein Emil, Helga Refsum, Lorentz M Irgens, Barbro Mork Emblem, Aage Tverdal, Håkon K Gjessing, Anne Lise Bjørke Monsen and Per Magne Ueland, "Plasma total homocysteine, pregnancy complications, and adverse pregnancy outcomes: the Hordaland Homocysteine Study. American Journal of Clinical Nutrition Apr 2000. Accessed 3 Apr 2008.

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