Wow, it’s incredible how much your 39-week-old has changed since their newborn days! Aside from growing an incredible amount, your once-tiny bundle is likely now babbling, trying exciting new foods and exploring the world on all fours. Here’s a closer look at what baby’s working on this week—and how you can support them.

39-Week-Old-Baby Milestones and Development

Growth

On average, a 39-week-old boy is 28.3 inches long and weighs 19.6 pounds. The average size for girls at the 39-week mark is 27.6 inches long, weighing 18.1 pounds. At the nine-month checkup, your pediatrician will measure baby’s height, weight and head circumference to make sure their growth is on track. If you have any questions or concerns, this is the time to bring them up.

Emerging skills

At 39 weeks, baby may be crawling, pulling themselves up to stand and “cruising” on furniture—all in preparation for those first solo steps. (Get ready, they’re coming soon!) Baby’s also babbling up a storm. But don’t be surprised if all that bubbliness takes a backseat around strangers: It’s normal for baby to act clingy or fearful with unfamiliar people.

39-Week-Old Baby Health

Feeding

Baby’s working on eating more independently and exploring new tastes and textures, although most of their nutrition is still coming from breast milk or formula. Try to make it a point to offer more finger foods, which will encourage baby to self-feed and give them more opportunities to work on fine motor skills—including the soon-to-emerge pincer grasp. Just remember to steer clear of foods that pose a choking hazard (think grapes, hot dogs and popcorn for starters.) Talk to your pediatrician if you have any questions about what is and isn’t considered safe.

Sleep

Baby's sleep needs have stayed pretty consistent over the past few weeks. Your 39-week-old should be logging about 12 to 16 hours of sleep every 24-hour period, with nine to 12 of those hours at night and the rest spread out between a morning and afternoon nap. At least, that’s what you’re aiming for! It’s not uncommon for sleep interruptions to strike around this time, whether it’s because of teething, colds, developmental milestones or just plain wanting to hang out with you. (That’s sweet, baby, but come on!) Try to stay the course with a consistent sleep schedule, including naps. And if you're really struggling, it could be time to look into sleep training.

Common ailments

Stomach bug

If baby’s throwing up or having diarrhea, it could be a stomach bug, often caused by viruses like rotavirus. Make sure to keep baby hydrated and call your doctor for guidance. Check in with your provider if baby is peeing less than every four to six hours, is acting very sleepy or less alert, has a high fever or has blood in their poop or vomit.

39-Week-Old Baby FAQs

Is it okay to give baby restaurant food or takeout once in a while?

You’re enjoying your pizza or pad Thai—can baby try some? While it’s best to avoid giving baby overly salty foods or foods with added sugar before their first birthday, some restaurant fare is fine to share with baby. Stick with menu items that are less processed and soft enough for them to gum safely, like well-cooked meats or vegetables, beans or pasta.

I want baby to be comfortable in the water. Now that they're getting more mobile, should we look into swim lessons?

There's no evidence that swim classes for babies under one will prevent drowning risk, since infants can’t lift their heads out of the water well enough to breathe, according to the American Academy of Pediatrics (AAP). Of course, that doesn’t mean you can’t take your little one swimming for fun and to get comfortable with the water. And by the time baby turns one, they'll be ready to start reaping the water-safety benefits of swim lessons.

Timely 39-Week-Old Topics

It’s snack time!

Now that baby is likely eating three meals a day, it’s a good time to introduce a couple of healthy snacks into the daily routine, if you haven’t already. Try to serve a balance of protein, grains and fruits and veggies: Think plain yogurt with diced ripe strawberries or a banana, steamed broccoli florets with hummus or whole grain toast strips with a thin layer of nut butter. (Avoid any choking hazards!) Keep in mind that it’s okay if a snack is just a few bites. And if baby eats so much they’re not hungry for the next meal, don’t stress—as long as you’re serving nutritious foods, it’s all good.

Making bath time more fun

Baby can’t keep still in the tub? Consider adding some sensory bath toys to the mix to keep them entertained. Toys like stacking cups and floating boats will strengthen fine motor skills—and keep them distracted long enough for you to get them sudsed up. And don't overlook items from around the house. To baby, non-breakable cups, scoops and strainers can be just as exciting as regular toys. And since bath toys are notorious for building up scum and grime, make your life easier by looking for ones that are quick-drying and can be cleaned in the dishwasher. Try to let the toys air-dry between tub sessions by spreading them out on a clean towel.

Parent Tips

• Don’t stress over baby classes. Research shows that baby music and movement classes can support parent-child interaction and foster bonding. So if you've got the flexibility in your schedule and budget, by all means, take baby to that Saturday morning parent-and-me class. But don’t pressure yourself if classes aren't an option now—or you just aren't into them. There are plenty of other opportunities to interact with baby and strengthen your bond.

Products You Need at 39 Weeks

• Bath toys. Stacking cups, things that float and other sensory bath toys will delight baby and strengthen key motor skills.
• Overnight diapers. If baby’s sleeping longer stretches (hurray!) and keeps waking up wet, it might be time to upgrade to an overnight diaper—or upgrade your overnight diaper to a more absorbent one.

Weekly Activity For Your 39-Week-Old Baby

All that crawling, pulling up and cruising means baby might be ready to tackle a mini obstacle course. Set up things like couch cushions and blankets for them to crawl over—it’ll boost their gross motor skills and they’ll have a blast with sensory exploration. Just be sure to keep an eye on them during this exploratory activity.