二人は結婚三年目に第１子を授かった。
They were blessed with their first child in the third year of their marriage.
彼女は先月、第１子となる男の子を出産した。
Last month she gave birth to a boy, her first child.
第１子の誕生をきっかけに、彼は育児休業を取った。
He took parental leave when his first child was born.
第１子の子育ては分からないことばかりで不安だった。
Raising my first child was full of things I didn't understand, and I felt anxious.