Further evidence of male offspring preference for certain subgroups in the United States (2007-2015).

INTRODUCTION

Males are born in excess of females. This ratio (M/T=male/total births) is influenced by various factors. A recent study showed that M/T in the United States (US) is Asian or Pacific Islander>White>American Indian or Alaska Native>Black or African American. This study was carried out in order to ascertain whether there are M/T differences in different races in the US by birth order.

METHODS

Monthly male and female live births by race and birth order for the entire US were obtained for 2007-2015 with birth order as 1-≥6 for these races.

RESULTS

There were 36,499,163 births. M/T decreased with increasing sibling order for all races (p<0.0001) except for Asian or Pacific Islander births where M/T rose progressively to 3rd order births (p<0.0001) then fell (p=0.0002). Weighted mean maternal age for each birth order by race order was Asian or Pacific Islander>White Black or African American/American Indian or Alaska Native. The differences between adjacent means were all significant (almost all p<0.0001). The mean maternal age spread followed the same order.

DISCUSSION

Asians favour male offspring. This group may be systematically implementing foetal sex-specific feticide and/or implementing a Type1 stopping rule when a male birth is achieved in order to maximise male births. The potential putative effect of increasing maternal age to decrease M/T is not only excluded in this race, but goes contrary to the findings of this study insofar as Asian or Pacific Islander births have the oldest mean maternal ages. Son preference strongly persists in the US.