LONDON — Prime Minister Boris Johnson’s life has always had a you-can’t-make-this-up quality to it, never more so than this month, when he went from desperate coronavirus patient, kept alive by oxygen, to the proud father of a baby boy — his fifth, sixth or seventh child, depending on who’s counting.

The announcement by Mr. Johnson and his fiancée, Carrie Symonds, that she gave birth to a healthy baby at a London hospital on Wednesday added a joyful milestone to a year of dizzying highs and lows: an election victory, a divorce, an engagement and a life-threatening illness — not to mention Brexit and a world-altering pandemic, which has killed more than 26,000 people in the country Mr. Johnson leads.

The latest twist in the Boris chronicles deprived political commentators of an important, if less anticipated moment: the prime minister’s first scheduled face-off in Parliament with the Labour Party’s new leader, Keir Starmer, at a time when the government’s handling of the virus has come under intense fire.

Mr. Johnson, who returned to work on Monday, skipped the session because of his son’s birth. Mr. Starmer raised difficult questions about the rising death toll and the lack of testing or protective masks for health workers, but he prefaced them with congratulations to Mr. Johnson, 55, and Ms. Symonds, 32, who also suffered symptoms of the virus but was reported to be healthy.