Related Experiment Videos
The human sex ratio: increase in first-born males to parents with shared HLA-DR antigens
Insights
Maternal-fetal HLA-DR antigen sharing influences offspring sex ratio. Male births are more common in first-borns compatible with mothers, especially when both parents share HLA-DR antigens.
Area of Science:
- Immunogenetics
- Reproductive biology
- Human genetics
Background:
- Maternal-fetal antigen sharing, specifically Human Leukocyte Antigen-DR (HLA-DR), is linked to pregnancy outcomes.
- Previous research suggests a connection between HLA-DR sharing and the sex ratio of newborns.
Purpose of the Study:
- To investigate the association between parental HLA-DR antigen sharing and offspring sex ratios across different birth orders.
- To compare sex ratios in families with and without HLA-DR sharing.
Main Methods:
- Studied 66 families with parental HLA-DR sharing and 61 families without.
- Analyzed offspring sex ratios and birth orders in relation to maternal-fetal HLA-DR compatibility.
Main Results:
- A significant excess of male first-borns was observed in HLA-DR compatible pregnancies compared to incompatible ones.
- Male births may remain elevated in higher birth orders for couples sharing both HLA-DR antigens.
Conclusions:
- Maternal-fetal HLA-DR compatibility may favor male offspring, potentially explaining the general male birth excess.
- The H-Y antigen in male fetuses might stimulate successful pregnancies in HLA-DR compatible cases.
Abstract:
Maternal-fetal HLA-DR antigen sharing has been reported to affect the sex ratio of first-born. We therefore studied offspring sex ratios and birth orders in 66 families in which parents shared one or more HLA-DR antigens as compared to 61 families with no parental HLA-DR sharing. A significant excess of males was found among first-born children who were HLA-DR compatible with their mothers compared to first-born HLA-DR incompatible children of couples sharing HLA-DR antigens and couples not sharing HLA-DR antigens. Increased numbers of males may persist among children of higher birth orders in families where parents share both HLA-DR antigens, but not among couples sharing only one HLA-DR antigen. We hypothesize that the presence of the H-Y antigen in the male fetus may provide the necessary stimulus for a successful pregnancy in HLA-DR compatible pregnancies and may explain the excess of male births in the general population.