Preemie Milestones: Premature Baby Development Week by Week Guide

By: Claire B. Crompton, RNC-NIC
Claire is a registered nurse with a certification in neonatal intensive care nursing. She has years of experience taking care of moms and babies in postpartum and neonatal intensive care units and has taught childbirth education classes to new parents. 

Having a premature baby is an intense experience that dramatically alters your expectations. While every baby accomplishes their preemie milestones at their own pace, this overview of premature baby development week by week can help you anticipate your baby’s developmental achievements.

What are the Milestones for a Preemie Baby?

Preemie development milestones are goals your baby will accomplish before going home from the neonatal intensive care unit (NICU).Your hospital may have discharge goals in addition to these common milestones for preemies:

  • regulating their body temperature 
  • breathing effectively 
  • gaining weight 
  • learning how to feed

Even though your baby is being cared for 24/7 by highly trained healthcare professionals, being temporarily separated from your baby is difficult. If you are the one who has given birth, try to take care of yourself with these postpartum recovery tips. Your well-being is key to your ability to be there for your little one.

What Does Premature Baby Development Week by Week Look Like?

Although being born early can sometimes result in medical complications and temporary setbacks, premature baby development week by week happens in the same progression as it would in the womb. Some babies achieve these developmental milestones earlier, while others need a bit more time.

The Early Weeks of Premature Baby Development (23 to 32 Weeks Gestation)

At 23-26 weeks, your baby may not be able to open their eyes, but their ears are fully formed and they can hear your familiar voice. Their skin is also developing and is quite fragile. The NICU staff will teach you how to gently touch and comfort your baby.

Because they are so small, it is difficult for preemies to regulate their body temperature. Your baby will spend lots of time inside an incubator during these early weeks of preemie baby development. This warmed environment helps your baby devote their energy to developing and gaining weight.

Premature babies’ lungs aren’t mature and they may need medication and oxygen support to help them breathe. They also haven’t fully developed the part of their brain that consistently triggers breaths. This causes 15-20 second pauses in their breathing, known as apnea of prematurity. Your baby’s medical team will monitor their vital signs and help them with oxygenation if needed.

Initially, your baby will receive intravenous (IV) fluids containing all the nutrients they need until they are medically stable and ready to start feeding. Even though their digestive system may be ready, your baby has not developed the ability to coordinate sucking, swallowing, and breathing. Because they often need help with this premature baby milestone, NICU infants are fed through a tiny flexible feeding tube that is passed through their nose or mouth, down their esophagus, and into their stomach. 

Around 26-28 weeks, your baby may reach an important preemie milestone: opening their eyes! Their developing neurological system isn’t able to handle lots of stimulation such as bright lights or loud sounds. As you spend more time with your baby, you will learn their overstimulation cues and know when they need rest. If your preemie is medically stable, you can hold them on your chest skin-to-skin, also known as kangaroo care. This can help soothe your baby and stabilize their vital signs as well, so try to do it as much as possible.

By 28-32 weeks of premature baby development, your baby’s tolerance for sensory stimulation will increase, but they can still be easily overwhelmed and may shut their eyes in bright light. You might observe them responding to your voice and maintaining eye contact. As your baby becomes more alert, continuing kangaroo care can facilitate bonding and provide comfort to you and your baby.

Preemie Milestones During Transitioning Weeks (33 to 37 Weeks Gestation)

Your baby may begin to show feeding cues such as sticking out their tongue or smacking their lips around 33-34 weeks. Once the medical team has determined your baby is ready, they can begin working towards one of the more challenging preemie baby milestones; learning how to feed from the bottle or breast. Patience is essential because this process takes time.

As your baby grows, their incubator’s temperature will be gradually decreased until it is no longer needed. As long as your baby has achieved the preemie milestones of maintaining adequate weight gain and regulating their body temperature, they can be moved to an open crib. This is one of the more enjoyable premature baby milestones for your little one because now they can be swaddled. Swaddlingwith plenty of room for your baby’s legs to bend can help avoid unhealthy hip joint development and dislocation.  

The open crib sleeping environment is similar to the one they will have at home. To learn more about setting realistic expectations for premature baby development week by week for sleep and creating a nurturing environment, read this article about what to know about sleep when bringing home a NICU baby. Establishing safe and healthy sleep habits early is essential for preemie baby development and everyone’s well-being.  

Typically, around 35 weeks, apnea of prematurity starts to resolve on its own and is not known to cause other health or developmental issues. Once a baby has stopped having these episodes, they will likely never happen again. Your baby’s medical team will be watching them closely to determine when they have reached this stage of premature baby development.

If your baby is medically stable, they can be entertained and comforted by one of the NICU’s MamaRoo® Multi-Motion Baby Swing™. Thanks to 4moms’ commitment to supporting NICU families through the 4moms Cares program, NICU babies can enjoy the MamaRoo’s variety of calming sounds and natural motions and its ability to mimic parental movements. Babies aren’t the only ones who love the MamaRoo. Read this article for a NICU nurse's perspective on its benefits.

Developmental Milestones for Preemies Nearing Full-Term (37 to 42 Weeks Gestation)

Your baby has made huge strides in overcoming the common hurdles of preemie baby development and is getting close to going home. As they continue to develop and reach new preemie milestones, you can expect them to be more social as they explore their environment through touch. Massage can help them develop their sense of touch as well as offering soft toys and smooth fabrics of various textures. Their vision is continuing to develop and they may like objects with contrasting colors such as black and white, although faces are their favorite things to look at. Your baby will enjoy having unswaddled play time while supervised on a play mat or in a  MamaRoo Baby Swing. Allowing your baby to move freely helps strengthen their muscles and develop their motor skills - both crucial milestones for preemies.

Premature Baby Milestones for Homecoming and Beyond (42 Weeks to 3 Months)

Bringing your baby home from the NICU is a huge accomplishment and transition for your family. To help prepare for your baby’s homecoming and continue reaching preemie milestones at home, check out this article 12 must-haves for bringing home a preemie baby, for a list of essential items and helpful advice. You can make the adjustment to home life easier by talking, reading, and singing to your baby. Doing these activities throughout a flexible routine can stimulate their language development, calm them, and give them a sense of security and predictability. Having your own MamaRoo Multi-Motion Baby Swing can also be helpful in the transition to home life. Your baby will enjoy the familiar motions and sounds and you will enjoy the Bluetooth and voice control features that provide hands-free convenience.

Do NICU babies hit newborn developmental milestones later?

Premature babies’ progression towards their standard developmental milestones, is tracked according to their adjusted age. Adjusted age is calculated by subtracting your baby’s actual age minus the number of weeks they were born early. For example, if your baby was born 8 weeks early their adjusted age will be 4 months when they are 6 months old. You can expect them to have developmental skills similar to a 4-month-old baby who was born full-term. Try to keep this in mind when setting preemie developmental milestones and comparing your baby to others of the same chronological age.

How long does it take a preemie to catch up?

Every baby develops at their own pace. Most preemies catch up to the typical milestone range by age 2. If your child doesn’t seem to be on track by this time, their pediatrician can connect you with resources for extra preemie baby development support.

Celebrating Premature Baby Development Week By Week

Supporting your premature baby requires lots of patience. It is helpful to remember that they are very resilient, and you are too. Your baby will accomplish their preemie milestones in their own time. Having a preemie is challenging, but you are not alone. The healthcare professionals in the NICU are there to provide guidance and support. As you love, care for, and support your premature baby, take time to celebrate each milestone they achieve, in the NICU and beyond.