Your 39-Week-Old Baby: Development, Milestones, and More

At 39 weeks old, your baby is undergoing significant changes and reaching new milestones. This period is marked by rapid physical, cognitive, and emotional development. Understanding what to expect can help you support your baby's growth and navigate any challenges that arise. From sleep patterns to social interactions, this guide covers all aspects of your 39-week-old baby's development.

Key Takeaways

  • Your 39-week-old baby is likely experiencing rapid physical growth, including changes in height, weight, and motor skills.
  • Cognitive and emotional development are also progressing, with advancements in language, communication, and problem-solving skills.
  • Sleep patterns may be evolving, with potential changes in nighttime sleep, napping schedules, and the possibility of sleep regression.
  • Feeding and nutrition remain crucial, with the introduction of new foods and the continuation of breastfeeding or formula feeding.
  • Social interactions and bonding activities are essential for building trust, security, and emotional connections with your baby.

Physical Growth and Changes

At 39 weeks, your baby is experiencing significant physical growth and changes. Tracking your baby's development is crucial during this period.

Height and Weight

Your baby's height and weight are important indicators of their overall health. Enter the baby growth chart, the major tool your pediatrician uses to plot your baby's physical development at every wellness checkup. This chart helps you understand how your baby compares to average growth patterns.

Motor Skills Development

Motor skills are rapidly advancing at this stage. You might notice your baby becoming more adept at crawling, standing, or even taking those first wobbly steps. These milestones are exciting and signify your baby's growing strength and coordination.

Teething Troubles

Teething can be challenging for both you and your baby. The discomfort and irritability from emerging teeth can disrupt sleep and feeding routines. Providing comfort and care during this phase is essential to help ease your baby's discomfort.

Cognitive and Emotional Development

At 39 weeks, your baby is making significant strides in their cognitive and emotional growth. This period is marked by rapid advancements in their ability to understand and interact with the world around them. It's a fascinating time to observe their development.

Sleep Patterns and Routines

Nighttime Sleep

At 39 weeks, your baby’s nighttime sleep might still be a bit unpredictable. Establishing a consistent bedtime routine can make a world of difference. Emphasize the difference between night and day by keeping nighttime interactions calm and quiet. Put your baby to bed drowsy but awake to help them learn to self-soothe.

Napping Schedule

Daytime naps are just as important as nighttime sleep. Aim for 2-3 naps a day, but be flexible as every baby is different. A good nap schedule can support better nighttime sleep and overall mood. Remember, a well-rested baby is a happy baby!

Sleep Regression

Sleep regression can be a challenging phase, but it’s completely normal. Around this age, your baby might experience disruptions in their sleep patterns. This could be due to developmental milestones or teething. Stay consistent with your routines and offer extra comfort as needed. Here's a guide to everything you need to know about a preterm baby's sleep—from the right sleep schedule and feeding tips to how to support their sleep.

Feeding and Nutrition

Introducing New Foods

Introducing new foods to your baby can be an exciting adventure. At 39 weeks, your little one might be ready to explore a variety of tastes and textures. Is baby ready for solids? Here are the top eight real and healthy first foods to start your baby on the right foot. Plus, three common first foods to avoid. Consider starting with mashed or pureed options like bananas, avocados, and cooked apples. These foods are not only nutritious but also easy for your baby to digest.

Breastfeeding and Formula

Whether you are breastfeeding, formula-feeding, or doing a combination of both, it's important to ensure your baby is getting the right nutrients. Breast milk provides essential antibodies and nutrients, while formula can be a convenient alternative or supplement. Pay attention to your baby's hunger cues and feed them on demand to keep them satisfied and healthy.

Healthy Eating Habits

Establishing healthy eating habits early on is crucial for your baby's development. Encourage a balanced diet that includes a variety of fruits, vegetables, grains, and proteins. Avoid sugary snacks and focus on whole foods to set the foundation for lifelong healthy eating. Remember, your baby is learning from you, so be a role model by making nutritious choices yourself.

Playtime and Activities

Interactive Games

Engaging your 39-week-old baby in interactive games is a fantastic way to support their development. Peek-a-boo and simple hide-and-seek games can be incredibly entertaining and educational. These activities help your baby understand object permanence and improve their social skills. Remember, while every baby develops at their own pace, you can use this list of expert-approved baby milestones to learn what to expect during that first year.

Outdoor Adventures

Taking your baby outside for some fresh air and exploration can be a delightful experience. Whether it's a stroll in the park or a visit to the playground, outdoor adventures offer numerous sensory experiences. The different sights, sounds, and textures can stimulate your baby's senses and foster a love for nature. Plus, it's a great way for you both to get some exercise and enjoy the outdoors.

Sensory Play

Sensory play is crucial for your baby's cognitive and emotional development. Activities like playing with textured toys, water play, or even exploring a sandbox can provide endless entertainment. These activities are organized and color-coded based on the age of your baby, starting from weeks 0-12 and moving up every three months. Sensory play helps in building neural connections in the brain and enhances problem-solving skills. So, get creative and let your baby explore different sensory experiences!

Health and Safety Tips

Babyproofing Your Home

Ensuring your home is safe for your little explorer is crucial. Start by securing heavy furniture to the walls and covering electrical outlets. Don't forget to install safety gates at the top and bottom of stairs. Keep small objects out of reach to prevent choking hazards. Regularly check for any potential dangers as your baby becomes more mobile.

Common Illnesses

At 39 weeks, your baby might encounter common illnesses like colds or ear infections. It's essential to recognize the symptoms early and consult your pediatrician when necessary. Keep a well-stocked first aid kit and maintain a clean environment to reduce the risk of infections. Remember, responsive settling can help comfort your baby when they're feeling unwell.

Related: Playdates offer a great opportunity

Vaccination Schedule

Staying on top of your baby's vaccination schedule is vital for their health. Ensure you follow the recommended immunizations and keep track of upcoming appointments. Vaccinations protect your baby from serious diseases and contribute to their overall well-being. Consult your healthcare provider for any concerns or questions about the vaccination timeline.

Social Interaction and Bonding

Playdates and Socialization

At 39 weeks, your baby is becoming more curious about the world and other children. Organizing playdates can be a fantastic way to encourage social skills. Playdates offer a great opportunity for your baby to learn sharing, empathy, and communication. Plus, it's a wonderful chance for you to connect with other parents and build a support system.

Family Bonding Activities

Spending quality time with family is crucial for your baby's emotional development. Simple activities like reading a book together, singing songs, or even a family walk can strengthen your bond. These moments help in forming attachment and provide a sense of security for your baby.

Building Trust and Security

Trust is the foundation of a strong parent-child relationship. Promptly and consistently responding to your baby's needs helps build trust. This not only makes your baby feel secure but also fosters a healthy emotional environment. Remember, your responsiveness plays a key role in your baby's overall development.

Social interaction and bonding are crucial for your baby's development. Our curated monthly baby boxes are designed to foster these essential connections through play and learning. 

Visit our website to explore our subscription options and give your baby the best start in life.


As your baby reaches the 39-week milestone, it's a time filled with excitement, curiosity, and rapid development. From new physical abilities to cognitive leaps, every day brings something new to marvel at. Remember, every baby is unique and will hit milestones at their own pace. Enjoy these precious moments, support their growth with love and patience, and don't hesitate to reach out to healthcare professionals if you have any concerns. Here's to many more weeks of discovery and joy with your little one!

What to read next

123 Baby Box sources ideas for their blog content from a variety of channels including feedback from subscribers, trending topics in baby care, and insights from industry experts. They aim to cover topics that are both informative and relevant to the needs and interests of parents and caregivers.

The writing process at 123 Baby Box typically involves several steps. First, they outline key points to cover in the article based on thorough research.

123 Baby Box publishes new content on their blog on a weekly basis. This regular schedule helps keep their audience engaged and informed about the latest in baby care, product recommendations, and parenting tips.

The blog posts for 123 Baby Box are typically written by content writers who specialize in parenting, child development, and health. These writers often have backgrounds in journalism, education, or healthcare, providing them with the expertise necessary to produce reliable and valuable content for parents.

123 Baby Box writers put in a lot of time researching and fact checking each article.

123 Baby Box is a subscription service that provides monthly boxes filled with products tailored for babies and toddlers.

Baby Box Subscription

Monthly subscription box for babies aged 0-3 years - delivering unique, fun products

star star star star star
(5.0 rating)
take baby quiz