The Fourth Trimester: What to Expect and How to Thrive
If your baby could send you a text from the womb, it might say, «Please don’t evict me!» At around 40 weeks, babies aren’t quite ready to thrive in the outside world without a lot of hands-on help. In fact, humans are born with the least-developed brains of any primate—researchers estimate that an additional nine to 12 months in utero would be needed to bring human babies to the same neurological and cognitive level as our primate cousins.
Evolution plays a role here: one theory suggests that as humans evolved to walk upright, women’s pelvises became narrower, making it harder and more dangerous to give birth to our large-headed babies past 42 weeks. This evolutionary trade-off means that for the first three months after birth—often referred to as the fourth trimester—your baby still needs significant care as they continue to mature and adjust to life outside the womb.
What Is the Fourth Trimester?
The concept of the fourth trimester was introduced in the late 1970s and popularized by pediatrician Harvey Karp in his 2002 book, The Happiest Baby on the Block. Karp’s work emphasizes treating newborns as if they are still fetuses outside the womb, helping them adjust to the world by recreating the sounds, movements, and snugness they experienced in utero. His method, known as the «5 S’s,» has helped countless parents soothe their fussy infants.
During the fourth trimester, your baby is adapting to life outside the womb, and you’ll be working to help them feel secure and comfortable in this new environment. «The first three months involve lots of cuddling and extra care,» says Ana Hernandez-Puga, MD, a pediatrician in Kendall, FL. For nine months, your baby was in a warm, noisy, and comfortable environment, constantly moving with you. Suddenly, they’re in a colder, quieter nursery and confined to a crib—a big change! This adjustment period can be challenging for both baby and parents.
What to Expect During the Fourth Trimester
Every newborn is different, and each one will handle the transition from womb to world in their own way. Some babies are naturally more mellow, while others may require more soothing. According to Karp’s The Happiest Baby Guide to Great Sleep, newborns emerge with four basic abilities:
- Life Support Controls: These are the most innate functions, such as heart rate and breathing.
- State Control: This refers to the baby’s level of alertness. Learning to control this is one of the brain’s first big tasks.
- Reflexes: These are inherent instincts that help the baby suck, sneeze, cry, and perform other basic actions.
- Muscle Control: Initially, muscle movements are tiny and uncoordinated, but they will become more refined over time.
During this period, your interactions with your baby—through eye contact, talking, and touching—help their brain cells develop rapidly. While they can see, hear, and feel from birth, their vision is blurry, and they’ll first identify you by your scent.
Crying is your baby’s primary way of communicating their needs, whether it’s hunger, discomfort, or the desire to be held. “You can never spoil a baby in these first few months,” says Hernandez-Puga. In fact, promptly and consistently responding to your baby’s fussing in the first six months may make them less demanding as they grow older.
Over the next few weeks, you’ll notice your baby sleeping for longer stretches, feeding more regularly, and interacting more with you through cooing and gurgling. By 2 or 3 months, your baby will start to engage in social interactions, such as smiling back at you when you smile at them.
Tips for Helping Baby Through the Fourth Trimester
Even if your baby is generally easygoing, expect some fussiness, especially in the first few weeks. Regularly check for hunger, dirty diapers, and the need to burp. If your baby is still fussy, you may need to try different soothing techniques:
- Skin-to-Skin Contact: Holding your baby close, with both of you wrapped in a blanket, can be very soothing as it mimics the warmth and closeness of the womb.
- Motion: Walking, dancing, placing your baby in a swing, or taking a car ride can help them relax.
- A Warm Bath: Some babies find warm water relaxing, and it can help establish a bedtime routine.
If these techniques don’t work, your baby might be overstimulated, gassy, overtired, or all three. Harvey Karp’s 5 S’s can help soothe your baby:
- Swaddle: Snugly wrapping your baby in a blanket helps recreate the security of the womb and reduces the startle reflex that can wake them up.
- Side/Stomach Position: Holding your baby on their side or stomach on your lap, or over your shoulder, can be soothing. However, always put your baby to sleep on their back to reduce the risk of SIDS.
- Shushing: Making shushing sounds in your baby’s ear, initially as loud as their cry, can mimic the noises they heard in the womb.
- Swinging: Gently jiggle your baby in small movements, supporting their head, to help them calm down.
- Sucking: Offer a pacifier or let your baby suck on their thumb or finger to soothe them.
Tips for Helping Mom Through the Fourth Trimester
Caring for a newborn is exhausting. Mothers typically get about 6.5 hours of sleep per day, but it’s often broken into short segments, which can lead to severe sleep deprivation. This can contribute to postpartum depression, marital distress, and even increase the risk of SIDS if you’re so tired that you accidentally fall asleep with your baby in bed.
To prepare for the fourth trimester, Kimberly Ann Johnson, author of The Fourth Trimester: A Postpartum Guide to Healing Your Body, Balancing Your Emotions, and Restoring Your Vitality, recommends creating a detailed plan during your third trimester. This plan should focus on meeting your essential needs: rest, nourishing food, loving touch, companionship, and contact with nature. Here are some tips from Johnson’s worksheets:
- Plan for Support: Compile a list of trusted visitors who can help you in the first few days and weeks after birth. These people can hold your baby while you shower, nap, or talk.
- Prioritize Rest: Think about how you’ll manage visitors and unplug from technology to ensure you get the rest you need.
- Organize a Meal Train: Arrange for meals to be delivered so you don’t have to worry about cooking while caring for your newborn.
- Minimize Commitments: Keep your responsibilities outside the home to a minimum during this time.
- Keep Resources Handy: Have contact information for essential professionals, such as a pelvic floor specialist, lactation consultant, doula, or housekeeper.
- Nurture Your Spirit: Keep a list of things you enjoy, like movies, songs, books, and activities, to help keep your mind and spirit nourished.
“Women need the same care that babies need postpartum,” Johnson says. To provide the care expected of a new mom—eye contact, swaddling, frequent feeding—you also need to be cared for and supported.
Conclusion
The fourth trimester is a critical time for both you and your baby. By understanding what to expect and planning ahead, you can navigate this challenging period with greater ease. Remember, taking care of yourself is just as important as taking care of your baby—both of you need plenty of love, support, and patience during this time.