|Questions of A More Technical Nature|
Blood Type and Sex Ratio
Sex ratio in man: an analysis of the relationship with ABO blood groups and placental alkaline phosphatase phenotype.
Hum Hered 1979;29(3):143-6
Gloria-Bottini F, Polzonetti A, Lucarini N, Palmarino R
Secondary sex ratio (SR) in man is influenced by various genetic and environmental factors. It has been observed that SR in subjects of blood group B compatible with their mothers is higher than in other subjects. The analysis of 676 newborns of the Rome population and 1,684 newborns of the New Haven (Connecticut) population have confirmed a higher SR in B group subjects compatible with their mothers. The data also indicate that placental alkaline phosphatase is another genetic factor influencing SR in man and that there is a strong interaction among ABO phenotype, fetomaternal ABO compatible status and PAP phenotype concerning their effects on SR.
Sex ratios are the number of males/the number of females in humans.
The Primary Sex Ratio is defined as the sex ratio at the time of conception whereas the Secondary Sex Ratio is the sex ratio at the time of birth. (1.06 in the US)
Usually, the sex ratio (numbers of boys born divided by the numbers of girls born) is slightly greater than one. In fact, world-wide about 106 boys are born for every 100 girls. This number is also reported as the male proportion of total births, or 106/206 = 0.514 = 51.4%.
This study indicated that offspring who are type B, and who are compatible with the mother (i.e the mother is either B or AB) have a higher percentage of boys to girls at birth. Interestingly the authors speculated that alkaline phosphatase may have been an influencing factor, in which case we can assume that the secretor status of the mother (i.e. AB or B secretors) is the phenotype with the highest sex ratio.