expression, noun
the dreaded third week (of a newborn's life)
Colloquial parenting term referring to the period around the third week after birth when some previously calm babies become fussy or colicky.
魔の３週目に入って、赤ちゃんが急に泣き止まなくなった。
We've entered the dreaded third week, and the baby suddenly won't stop crying.
魔の３週目は多くの親が経験するらしい。
It seems many parents go through the dreaded third week.
Refers to the 'terrible twos' phase in toddlers, while 魔の３週目 is specific to newborns around three weeks old.
The expression literally means 'the devil's third week,' reflecting the sudden onset of fussiness that can feel inexplicable to new parents. The exact origin is uncertain, but it is a common colloquialism in Japanese parenting circles.