Burning coal for domestic heating may contribute to early fetal death according to a new study by conducted by experts in Mongolia from the Saban Research Institute of the Children”s Hospital of Los Angeles. In a paper published recently in the journal BMC Pregnancy and Childbirth, researchers report that “alarmingly strong statistical correlations” exist between seasonal ambient air pollutants and pregnancy loss in Ulaanbaatar.

Reports state that Ulaanbaatar has one of the world’s highest levels of air pollution, with sulfur dioxide and particulate matter levels during winter months reaching up to 23 times World Health Organization standards.

The researchers, led by David Warburton, professor of Pediatrics and Surgery at the Saban Research Institute of the Children”s Hospital of Los Angeles, and the Keck School of Medicine at the University of Southern California, examined the association between spontaneous abortion, or miscarriages, and the seasonal variations of air pollutants in Ulaanbaatar.

The measurements were gathered near the National Center for Maternal and Child Health which provides the majority of obstetric and gynecological services in the city. The results were compared to the medical records of 1,219 women in the area who had been admitted to the hospital between 2009 and 2011 due to fetal death prior to 20 weeks gestational age.

While the overall rate of miscarriages reported in UB is similar to that of Western countries, including the United States, the study showed that spontaneous abortion incidence per calendar month increased from 23 per 1,000 live births in May, to 73 per 1,000 live births in December 2011.