At four months postpartum, you’re past the raw survival mode of the newborn phase but likely facing a new set of challenges. Your body is still actively recovering, your hormones are shifting, your baby is hitting a major developmental leap, and sleep may have suddenly gotten worse. Here’s what’s actually happening at this stage and what to look for.
The 4-Month Sleep Regression
If your baby was sleeping in longer stretches and suddenly isn’t, you’re not imagining things. Around four months, babies undergo a permanent change in how they sleep. In the early weeks, infants spend most of their sleep time in deep sleep. By four months, their brains start cycling between deep and light sleep phases, much like adults do. The problem is they haven’t learned how to transition between those phases smoothly, so they wake up more often, sometimes every one to two hours.
This isn’t a setback. It’s a sign your baby’s brain is maturing. But it can feel brutal, especially if you’d just started getting longer stretches of rest yourself. The regression typically lasts two to six weeks. During that time, your baby may also resist naps, seem fussier than usual, and want to feed more frequently overnight.
What Your Baby Can Do Now
Four months is one of the more rewarding developmental stages. According to the CDC’s milestone checklist, by four months your baby should be holding their head steady without support when you hold them upright. They can grasp a toy placed in their hand, swing their arms at objects that interest them, and bring their hands to their mouth. On their tummy, they’re pushing up onto their forearms.
Socially, this is when things get fun. Your baby is smiling on purpose to get your attention, not just reflexively. They’re making cooing sounds (“oooo,” “aahh”), responding when you talk to them, and turning their head toward your voice. Some babies will chuckle at this age, though a full belly laugh may still be a few weeks away. They’re also starting to study their own hands with genuine curiosity, which is an early sign of understanding that their body belongs to them.
Postpartum Hair Loss Peaks Now
If you’re finding alarming clumps of hair in the shower drain or on your pillow, this is the most common time for it. Postpartum hair loss typically starts around three months after delivery, which means four months is often when it’s at its most noticeable. During pregnancy, elevated estrogen kept hair in its growth phase longer than usual, giving you thicker hair. Once those hormone levels dropped after birth, all that extra hair entered its shedding phase at once.
This is called telogen effluvium, and it’s not actual hair loss in the permanent sense. Your hair is returning to its pre-pregnancy thickness. The shedding usually resolves on its own between 6 and 12 months postpartum as your hair growth cycle resets. No special supplements or treatments are needed for most people, though keeping up with general nutrition helps.
Where Your Hormones Stand
Estrogen and progesterone actually return to pre-pregnancy levels within the first week after delivery, not months later as many people assume. What’s different at four months depends largely on whether you’re breastfeeding. If you are, prolactin (the hormone that drives milk production) remains elevated, which suppresses estrogen and can delay the return of your period. Many breastfeeding mothers won’t see a period for six months or longer, especially if they’re nursing frequently.
If you’re formula feeding, prolactin drops within a few weeks of birth, and your menstrual cycle may have already returned by now. Either way, you can ovulate before your first postpartum period arrives, which catches some people off guard.
Pelvic Floor and Physical Recovery
By four months, you’re past the 13-week mark where guidelines suggest return to higher-impact activity becomes possible. But “possible” doesn’t mean your body is fully recovered. Current rehabilitation timelines recommend that women wanting to return to running start around three months postpartum, then increase mileage gradually while monitoring for symptoms like leaking, pelvic pressure, or pain.
Practical benchmarks at this stage include being able to hold a single-leg calf raise, single-leg hop, jump in place, wall sit, and plank for 60 seconds each without symptoms. If you can’t do these comfortably, your pelvic floor and core may need more time or targeted work before you add running or jumping back into your routine. Cross-training with weights and lower-impact cardio helps build the foundation without overstressing tissues that are still healing.
The general recommendation from both ACOG and U.S. physical activity guidelines is at least 150 minutes of moderate-intensity aerobic activity per week during the postpartum period, spread throughout the week. If you were active before pregnancy, you can return to vigorous exercise. If you weren’t, building up slowly is the safer path.
Postpartum Weight Changes
Most postpartum weight loss happens in the first three months, then continues at a slower, steadier pace through about six months. If you feel like the scale has stalled at four months, that’s the normal pattern. Your body lost the bulk of pregnancy-related fluid, blood volume, and the placenta in those early weeks. What’s left is a more gradual process influenced by sleep, stress, breastfeeding, and activity level.
Putting pressure on yourself to “bounce back” at this stage works against you. Sleep deprivation alone raises cortisol and increases appetite, and the four-month sleep regression can make both worse. Focusing on consistent movement and adequate nutrition does more for long-term body composition than restricting calories, especially if you’re breastfeeding.
Mental Health at Four Months
Postpartum depression and anxiety don’t have an expiration date at six weeks. CDC data shows that about 12% of mothers report depressive symptoms between two and six months postpartum. Four months is a particularly vulnerable window because the initial wave of support from family and friends has often faded, sleep deprivation is cumulative, and the novelty of new parenthood has worn off.
The signs aren’t always dramatic. Feeling persistently down, hopeless, or losing interest in things you used to enjoy are the two core screening questions used in clinical settings. But postpartum mood disorders can also show up as irritability, rage, intrusive thoughts, difficulty bonding with your baby, or a sense of going through the motions without feeling present. Anxiety is closely linked to depression at this stage. Women with postpartum anxiety are more than three times as likely to also have depressive symptoms.
If you’re noticing these feelings most days, that’s worth paying attention to. Postpartum depression is highly treatable, and outcomes are better with earlier intervention.
Starting Solid Foods: Not Quite Yet
Your pediatrician may bring up solid foods at the four-month visit. The current recommendation from both the American Academy of Pediatrics and the Dietary Guidelines for Americans is to introduce solids at about six months. Starting before four months is not recommended. Some providers give the green light between four and six months for certain babies who show signs of readiness (sitting with support, showing interest in food, good head control), but six months remains the standard target. At four months, breast milk or formula still provides everything your baby needs nutritionally.