What is the 4th Trimester of Pregnancy?

The journey of bringing a baby into the world doesn’t end after childbirth. The 12 weeks after your baby is born, also referred to as the fourth trimester of pregnancy, is a time of continued growth and changes – and deserves just as much attention as the previous three trimesters.  

Here we’ll discuss more about what is the fourth trimester, what the fourth trimester for mom is like, what changes you may see in your baby during their first 12 weeks, and what else to expect at the beginning of your baby’s life.

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What Is the 4^th Trimester?

The fourth trimester refers to the first 12 weeks of your baby’s life and is also considered the newborn stage. It’s a time when your newborn transitions from the womb to the outside world and when you, as a parent, adjust to life with your new addition, while also healing from pregnancy and childbirth.

The 4th trimester is a period of significant physical changes for both you and your baby. Your baby experiences growth spurts, increased alertness, and rapid neurological development. Meanwhile, your body is recovering from pregnancy and childbirth, which includes hormonal shifts and your uterus returning to its pre-pregnancy size.

The 4^th trimester also brings emotional changes as you adjust to having a new human to care for. This is all on top of sleep challenges and exhaustion, as a baby doesn’t start to establish their circadian rhythm until at least 3-4 months of age.  

Why is it Called the 4^th Trimester?

The term "fourth trimester" refers to the first three months after birth, when a newborn is still very much adapting to life outside the womb – and very much still dependent on their mother like they were when they were in their belly.  

For example, like during the first three trimesters of pregnancy, babies continue to be dependent on others for feeding, comfort, and regulating temperature during the first 12 weeks after birth. Plus, they are also growing and changing rapidly, like they did in the womb.  

Additionally, it can be considered the 4^th trimester of pregnancy because just like how a mother’s body changes constantly during pregnancy, the body also continues to change and evolve after birth, with major physical, hormonal, and emotional changes happening during the first 12 weeks.  

While it takes months to adjust and heal from childbirth, the first 12 weeks are thought to be the period of biggest adjustment – especially given your baby doesn’t yet understand the difference between day and night.  

How Long is the 4th Trimester

Wondering how long does the 4^th trimester last or when does the 4^th trimester end? It lasts for 12 weeks after your baby is born, so ends around their 3-month birthday. Each trimester of pregnancy is around the same amount of time. If your baby is born prematurely, follow their adjusted age when it comes to the end of the 4^th trimester and their development.  

While the 4^th trimester ends around 12 weeks, your baby will continue to change well into their first-year. It also can take months for mom’s body to recover from pregnancy.

Once your baby reaches around 3-months-old, you will notice their schedule starting to take shape, which may even include more predictable day and nighttime sleep.

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What is the Fourth Trimester for Mom Like?  

There are many changes that a mom experiences during the fourth trimester and oftentimes that can change by the day as your body heals and your baby grows and reaches different developmental milestones. (Here’s a guide to baby developmental milestones by age).

Generally, the fourth trimester for mom includes both physical and emotional changes, on top of the excitement (and relief) of having your baby here. If you have any severe pain or thoughts of hurting yourself or your baby, seek medical care immediately.  

Physical changes during 4th trimester

During the 4^th trimester physical changes to expect may include:  

• Postpartum Bleeding: Also called lochia, postpartum bleeding is a normal sign that your body is cleaning out the uterus. Most moms experience postpartum bleeding for about 6 weeks after birth. It is heavier the first few days after birth and decreases overtime. While large clots can be considered normal, be sure to contact your healthcare provider if you’re bleeding more than this.

• Nipple and Breast Pain: If you’re nursing, breastfeeding and fourth trimester go hand-and-hand, as it’s during this time that you and your baby are getting used to feeding. Nipple pain often gets better as you get in the swing of things, as improper latch along with frequent feedings can cause sore, cracked skin on your nipples. As your milk comes in, your breasts can swell or feel sore. It’s important to empty your breasts often and watch for signs of infections or engorgement.  

• Pain and Soreness: Whether you had a vaginal birth or cesarian section, recovery will take time and can be challenging – it's important to rest as much as you can and take help from others when possible. Often it can take 6 weeks before your healthcare provider will clear you for pre-baby activities, including working out or sexual intercourse. While mild pain and cramping is expected, seek immediate medical care if you have a fever, large clots, or severe pain.

• Uterus Contractions: As your uterus shrinks back to its normal pre-pregnancy size (which can take around 6 weeks) you may feel mild period-like cramping, especially when you breastfeed.

• Colostrum: The first breast milk is called colostrum, which starts soon after birth and sometimes even before. It is full of important antibodies, which is why some call it Liquid Gold. It may not seem like much, but it is often sufficient for your new baby until your milk comes in (which takes a few days – when it happens your breasts will seemingly swell up and feel full).

• Your First Poop(s): Some say your first bowel movement after giving birth can feel like...giving birth. Whether you had a vaginal birth or cesarian, pushing may hurt, and you’re likely constipated from days in the hospital. Drink lots of water and eat high fiber food – your healthcare provider may recommend a laxative, too.

• Exhaustion: A new baby feeds around-the-clock, which means getting 8-hours of sleep in a row becomes non-existent – they can’t sleep through the night as a newborn. Sleep deprivation during the fourth trimester is challenging, especially as mom recovers. Reach out for support if and when you need it, whether it be from a partner, family member, or caregiver.  

Take this free 3-minute quiz to get your personalized plan for easing into life with a newborn – from weekly tips on managing the fourth trimester to a sleep schedule that helps optimize naps to keep baby sleeping longer stretches, it’s a game-changer for new parents.  

Emotional changes during 4th trimester

During the 4^th trimester emotional changes to expect may include:

• Baby Blues: It’s totally normal for the sudden changes in hormones to cause some feelings of sadness early postpartum. However, by week 3, “Baby Blues” often starts to lessen. If you’re still feeling anxious or depressed, reach out to your provider – postpartum depression is very common, and very treatable. There are ways to help you cope and feel more like yourself.

• Mood Swings: With the changes in hormones, emotions often run wild the first few weeks postpartum (sometimes even longer!) and mood swings can be expected. They should level off quickly but it’s not uncommon to just feel like crying and then start laughing the next minute. However, if you feel unable to cope or have negative thoughts, seek immediate medical care.  

• Bonding: Some parents feel an immediate connection with their baby, while others take time to adjust. Regularly having skin-to-skin contact with your newborn and continuing to meet your baby’s needs are natural ways to build and deepen your connection. (Did you know skin-to-skin also plays a part in baby sleep safety?)

• Identity Shifts: Adjusting to new roles and responsibilities can bring both joy and uncertainty, whether it be re-adjusting to work after having a baby or maintaining relationships. Becoming a parent does change things, and healthcare providers can provide you with resources if you're struggling with the shift.  

What to Expect for Baby During 4th Trimester

Your baby will be going through a lot of growing and changing throughout their first 3 months of life. Every week often looks different than the last!   Generally, there are some common milestones that a baby will reach at the end of each month of the 4^th trimester. (If you’re looking for weekly fourth trimester updates, download Smart Sleep Coach).

• 1-month-milestones: It can take a few weeks for your baby to “wake up”. They may sleep most of the day, waking every 2-3 hours (sometimes even more) for feeds to fuel their rapid growth – wake windows can be as short as 10 minutes. While a newborn can’t see too far in front of them, they will recognize their caregiver’s voice. Some parents may even see their baby’s first social smile by the end of the first month!  

• 2-month-milestones: Even though 2-month-olds still wake every 3-4 hours for feedings, all the physical, cognitive, and social milestones you’ll observe this month almost make you forget your sleep deprivation. When do babies roll over? It can start around this time (this is when you should stop swaddling) and also, they will be able to do tummy time for a bit longer. Also, smiles at wake ups, cooing when cuddling, and eye contact when you speak often are enjoyed around this time. The Witching Hour may peak around this time, which means increased and unexplained crying – it’s also normal...and there are ways for how to cope with the baby witching hour.  

• 3-month-milestones: This age is when your baby gains even more control over their body and senses, moving beyond reflexes (which is why babies move so much in their sleep). They are showing improved motor skills with purposeful movements, such as reaching for objects and stretching. Better vision, mimicking conversations, and social smiles help with both social bonding and recognizing patterns – like a consistent bedtime routine – are also signs your baby is getting ready to start sleeping better at night.

Making the Most of the Fourth Trimester  

Navigating the 4th trimester of pregnancy and beyond can feel overwhelming at times, but there are ways to help you make the most of it.

1. Hydrate, Eat, and Rest: Prioritize meals and snacks that nourish you, drink plenty of water, and rest whenever possible (easier said than done, we know).

2. Know What to Expect: Having a newborn can be stressful, as is not knowing what is and isn’t normal. The download the Smart Sleep Coach by Pampers^TM to get weekly updates on what to expect and what’s normal for your baby for the 4^th trimester, from poop colors to growth spurts to cluster feeds to nap schedule changes.    

3. Feed on Demand: Whether you’re breastfeeding or preparing formula, newborns need to eat frequently to fuel their rapid growth. Keep track of feedings to ensure your baby is getting enough.

4. Diaper and Sleep Tracking: Tracking sleep is the best way to start developing a predictable routine and prevent overtiredness, and tracking dirty diapers are a great indicator of proper feeding. You can track both with the Smart Sleep Coach app – it’s helpful for pediatric checkups and, if breastfeeding, for regulating your milk supply, too.  

5. Lean into Contact Naps: Many newborns only want to sleep when held. It’s totally normal, and a great way to bond with your baby. Just make sure you stay awake and transfer your little one to their crib on their back if you think you’re going to fall asleep.

6. Follow Wake Windows: Sleep patterns will be irregular until around 3 or 4 months but tracking naps and nighttime sleep in an app that follows wake windows can help know the optimal time for your baby to sleep, which can relieve a lot of stress.

7. Be Kind to Yourself: Every phase is temporary. While the fourth trimester has its challenges, it’s also an incredible period of bonding and discovery. If you’re ever struggling with how to soothe a crying baby, it’s okay to ask for help.

8. Reach Out for Help: If you’re feeling overwhelmed, exhausted, or unlike yourself, your healthcare providers are your best resource during this time. Don’t hesitate to reach out with questions about 4^th trimester healing, breastfeeding, or newborn care.  

Final Thoughts

While the fourth trimester officially ends after 12 weeks, the bond you’re building with your baby and the growth you’re experiencing as a parent will continue to flourish long after. Knowing what to expect for the 4^th trimester, and how long the 4th trimester lasts, can help you mentally and physically prepare for the challenges and joys ahead. By embracing this time with care, patience, and flexibility, you’ll create a nurturing environment for your growing family. And remember: this phase is temporary, so try and enjoy the ride.

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