Second children are more likely to be girls than first children: in 2021, there were 113 firstborn sons for every 100 firstborn daughters, but only 106 boys born second for every 100 girls.

2021 年， 每出生100 个一胎女婴，同时出生了 113 个一胎男婴；每出生100 个二胎女婴，同时出生了 106 个二胎男婴。