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Finding the link between miscarriage rates and X-inactivation

What’s the connection between miscarriage and inactivation of the X chromosome? That’s what Tracy Prosen‚ M.D.‚ assistant professor in the Division of Maternal-Fetal Medicine‚ hopes to find out.

Women have two X chromosomes in every cell‚ but as female embryos develop in utero‚ one of those chromosomes is shut off‚ or inactivated‚ so that each cell uses only one X chromosome. Normally‚ that inactivation is random; the X chromosome from either the father or the mother can be inactivated.

During skewed X-inactivation‚ however‚ the shut-off of the X chromosome is not random; instead‚ it is always‚ or nearly always‚ paternal or always maternal in origin. Researchers suspect that this unbalanced inactivation may result from the presence of an abnormal X chromosome‚ Prosen says.

Studies have shown that women with skewed X-inactivation have an average miscarriage rate of nearly 40 percent‚ compared with 15 percent in the general population. Prosen is studying when these miscarriages occur to help identify the cause of the phenomenon.