第だい一いっ子し

noun

firstborn; first child; eldest child

Refers to the first child born to a parent or couple. Neutral term used in family contexts, medical records, and official forms.

• 彼かの女じょは第だい一いっ子しを出しゅっ産さんしたばかりだ。

  She just gave birth to her first child.

• 第だい一いっ子しが生うまれたとき、夫おっとはとても喜よろこんだ。

  When their first child was born, the husband was overjoyed.