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Day 120 of 120 · Four months

Four months

Last reviewed · 4 min read · 14 sources · Plain-text version

The 4-month list as a celebration, not a score: chuckles, a steady head, hands that grab, a voice that answers. A third of a year done, and the next guide.

Two South Asian mothers on a sunlit living-room floor, one blowing a raspberry on their seventeen-week-old's belly as the baby lies on a blanket, head back, mid-chuckle, the other laughing.

Four months. A third of a year. Today's list is for celebrating, and nobody is keeping score.

Heart

By about now, many babies smile on their own to get your attention, chuckle when you try to make them laugh, look at you or move or make sounds to keep your attention, coo, make sounds back, turn toward your voice, open their mouth at the sight of the breast or bottle, look at their hands, hold their head steady when held, hold a toy you put in their hand, swing at toys, bring hands to mouth, and push up on forearms on their tummy (CDC). Those are the skills at least 75% of babies show by 4 months (Zubler et al., 2022); a missing one is a question for your pediatrician, not a grade. Born early? Corrected age, for the first 2 years (AAP).

Head

The first laugh, if it hasn't come, is close. Laughter first appears at about 4 months on average (Mireault et al., 2015); chuckles are the 4-month milestone and full laughs the 6-month one, so the window is wide (CDC; CDC). Your own laughter helps your baby figure out what's funny (Mireault et al., 2015), which is why the first one is almost always at something you did.

Body

A third of a year of feeding, holding, floor time, and nights. Longer night stretches are common now, not universal: in a London video study of 101 babies, 45% slept at least 5 hours straight by 3 months (St James-Roberts et al., 2015). Rolling, for the babies who've started, usually begins around 3 to 4 months (Moon, AAP). Whatever your baby's numbers are, they got there with you.

Try today

  1. One mother holding the baby upright on her lap making a loud silly face while the other kneels beside them writing on a sticky note stuck to the coffee table.

    The laugh collection

    Time: 5 minutes tonight, then whenever a new one turns up · Raspberry laugh game in the guide

    1. Write down, or record, three things that got a chuckle this month: a raspberry on the belly, a sound, a face, a song.

    2. Try each one now, and laugh along; your reaction is part of the game (Mireault et al., 2015).

    3. Mark which worked and which got a stare, and stop while it's still fun.

    4. Keep the list on the fridge where a sitter or grandparent can find it.

    Make it work:

    In the second half of the first year, babies start laughing at silly surprises, like a parent putting a book on their head (Mireault et al., 2015). Leave room on the list.

Watch for

  • Normal

    a chuckle, not a laugh, and some days neither.

    Raise it with your pediatrician

    if your baby doesn't smile on their own by 5 months (AAP).

  • Normal

    a stuffy nose from the fourth-month cold.

    Go to the ER now

    for any trouble breathing, including ribs pulling in with each breath or wheezing, and call 911 if your baby is struggling to breathe or has bluish lips or face (AAP).

  • Normal

    at 3 to 6 months, a fever is a call within 24 hours;

    call right away

    for 101°F (38.3°C) or higher, and get care now for a fever over 104°F (40°C) or a baby who looks very sick (AAP; AAP).

  • Normal

    not being sure whether something is wrong.

    Call anyway

    if your baby just doesn't seem right to you. Trust your instincts (Lurie Children's).

For you

The two mothers side by side on the sofa in evening light, the baby asleep on their back in the bare crib behind them, one resting her head on the other's shoulder, both eyes closed.

You did a third of a year. Nobody will give you the certificate, so here it is: one hundred and twenty days of answering, every one of them. If the mood underneath is heavier than tired, low mood, anxiety, or emptiness that is severe or lasts more than 2 weeks may be postpartum depression, and it responds to treatment (NIMH). Four months in is still early to ask for help, not late.

Once more, lightly: the National Maternal Mental Health Hotline is 1-833-TLC-MAMA (1-833-852-6262), call or text, and 988 is for anyone (CDC).

If you're the partner: you did it too, and the hotlines are yours as well. Tonight, say one thing she did this month that you noticed. Then go read what's next, together: the 4-month guide.

Sources

This guide is general education that summarizes published research and guidance from groups like the American Academy of Pediatrics, the CDC, and the WHO. It isn’t medical advice, and every child develops on their own timeline. Your pediatrician knows your child; if something feels wrong, call them. In an emergency, call 911.

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