single birth

例句：

1. 1. The single birth rate has been declining for several years.
   单胎出生率已经下降了几年。
2. 2. This is the first time we've had a single birth in our family history.
   这是我们家族历史上第一次有单胎出生。
3. 3. The doctors were surprised to find out that the baby was a single birth.
   医生们惊讶地发现，这个宝宝是单胎出生的。