Whether or not MECP2 Duplication Syndrome is associated with a higher rate of miscarriage during pregnancy remains an open question. Some families have reported a history of miscarriage in families carrying the duplication and voiced the question of whether there is a connection.
At this point there seems to be inadequate data to draw a conclusion. However, one research study crossed MECP2 Duplication Lab mice with other lab mice. Simple genetics would have predicted that 25% of offspring would have MECP2 Duplications, but researches found that only 11% of surviving offspring had the duplication (Alvarez-Saavedra et al., 2010). This strongly suggests that MECP2 duplication reduces the chances of fetal survival, but there might be some other explanation. In addition, even if true, the applications of these findings to humans is unclear.
So the question remains open at this time pending further research.
Alvarez-Saavedra, M., Carrasco, L., Sura-Trueba, S., Demarchi Aiello, V., Walz, K., Neto, J. X., et al. Elevated expression of MeCP2 in cardiac and skeletal tissues is detrimental for normal development. Human Molecular Genetics, 19(11), 2177-2190. [e-publication 2010/03/06].