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ABSTRACT
Male microchimerism, the presence of a small number of male cells, in women has been attributed to prior pregnancies. However, male microchimerism has also been reported in women with only daughters, in nulliparous women and prepubertal girls suggesting that other sources of male microchimerism must exist. The aim of the present study was to examine the presence of male microchimerism in a cohort of healthy nulliparous Danish girls aged 10–15 y using DNA extracted from cells from whole blood (buffy coats) and report the association with potential sources of male cells. A total of 154 girls were studied of which 21 (13.6%) tested positive for male microchimerism. There was a tendency that girls were more likely to test positive for male microchimerism if their mothers previously had received transfusion, had given birth to a son or had had a spontaneous abortion. Furthermore, the oldest girls were more likely to test positive for male microchimerism. However, less than half of microchimerism positivity was attributable to these factors. In conclusion, data suggest that male microchimerism in young girls may originate from an older brother either full born or from a discontinued pregnancy or from transfusion during pregnancy. We speculate that sexual intercourse may be important but other sources of male cells likely exist in young girls.
Abbreviations
| CI | = | confidence interval |
| DNBC | = | Danish National Birth Cohort |
| FMc | = | fetal microchimerism |
| GE | = | genome equivalents |
| HIP | = | hypertension in pregnancy |
| MMc | = | maternal microchimerism |
| OR | = | odds ratio |
Disclosure of potential conflicts of interest
No potential conflicts of interest were disclosed.
Acknowledgments
We thank Line Hjort for blood sample assistance, Anne-Marie Nybo Andersen for sharing DNBC experience, and Susanne Hansen and Marin Ström for data delivery and approval help.
Funding
The study was supported by Department of Public Health, University of Copenhagen. The Danish National Research Foundation has established the Danish Epidemiology Science Center that initiated and created the Danish National Birth Cohort. The cohort is furthermore a result of a major grant from this Foundation. Additional support for the Danish National Birth Cohort is obtained from the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, the Augustinus Foundation, and the Health Foundation.