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the definition in the dictionary is actually not akin to what folks are bitching about. yet we find often that nobody that is bitching about this is actually going to read the definition in the dictionary itself.

Definition of fourth trimester

: the three month period immediately following giving birth in which the mother typically recovers from childbirth and adjusts to caring for her infant.

The "fourth trimester" is a catchphrase used to describe the postpartum period, defined as the first 12 weeks after delivery. — Meera Varma Simões

Women and their families experience substantial physiological, social, and emotional changes. … Most women would benefit from much closer follow-up during the fourth trimester. — Ilona T. Goldfarb

especially : the first three months of an infant's life The concept of the fourth trimester—the three-month period of adjustment for babies to life outside of the womb—was introduced in the late 1970s and then popularized by pediatrician Harvey Karp … in 2002. — Maggie Overfelt

that last bit, note how it says 'babies' and then it says 'life'.

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