Your 44-Week-Old Baby

Now that baby is getting bigger, and if you're still using an infant car seat, you might be wondering when it's time to switch to a convertible one. 

The transition isn't always obvious—some parents make the switch when their baby hits a weight or height limit, others when lugging that heavy carrier starts to feel impossible. But knowing the right time to transition (and the common mistakes parents make during this stage) can help keep your baby as safe as possible. I talked to Dr. Chris Klunk, a board-certified neonatologist at Pediatrix Medical Group, and Jen LaBracio, Babylist’s senior gear editor and a certified child passenger safety technician (CPST), about when to make the switch, why rear-facing should continue as long as possible and what features actually matter when choosing a convertible car seat.

🚼 Baby’s Development 

When it's time to switch to a convertible car seat

If you’re wondering when it's time to move on to a convertible one, the good news: the signs are pretty straightforward once you know what to look for.

LaBracio explains that infant car seats are designed for newborns until your baby reaches the maximum height or weight allowed—typically around 30-32 inches or 30 pounds, depending on the model. "The 'or' is key," she says. "If your baby hits either limit, it's time to move on to a convertible seat."

But there's another sign that often comes first: the one-inch rule. Most infant car seats follow this guideline, which means there should be at least one inch of space between the top of your baby's head and the top of the car seat shell. If there's less than an inch of space, your baby has outgrown the seat, even if they haven't hit the listed height or weight limits yet.

LaBracio offers a simple trick for checking: "Place a one-inch-thick board book on your child's head while they're buckled in to help measure."

So the bottom line: if your baby exceeds the height limit, weight limit or the one-inch rule, it's time to move to a convertible car seat.

That said, you don't have to wait until your baby maxes out the seat. Convertible car seats can be used from birth, so as long as you can get a safe, snug fit, you can switch whenever it makes sense for your family. For many parents, LaBracio notes, that moment comes "when carrying the infant seat starts to feel like a workout—those things get heavy fast."

Keep them rear facing

Once you've made the switch to a convertible car seat, you might assume the next step is turning your baby forward-facing. But here's what matters most for car seat safety at this stage: keeping them rear-facing for as long as possible.

Why is this safer for children? Young kids have large, heavy heads and developing neck muscles, which makes this extra support especially important. "In a crash, a rear-facing seat supports your child's head, neck and spine and helps distribute crash forces across their entire body,” LaBracio says.

Dr. Klunk is straightforward about this: "The simple fact is that rear-facing is safer in a crash for as long as you can maintain it." This is also the American Academy of Pediatrics recommendation.

And before you worry about their legs being uncomfortable, "It doesn't matter if their feet are touching the seatback or if they have great head control," Dr. Klunk says. "The simple fact is that rear-facing is safer in a crash for as long as you can maintain it."

Don't rush the switch. Rear-facing is the safest position, and your baby can stay that way much longer than you might think!

Choosing the right convertible car seat

Once you're ready to buy a convertible car seat, there are a few key features to prioritize: 

• higher rear-facing limits (weight or height), so your baby can stay rear-facing longer

• a fit that works well in your specific vehicle

• easy installation

But you don't have to figure this out alone! Check out our convertible car seat guides to help you pick the best one for your family:

• The Best Convertible Car Seats

• I’m a CPST, and These Are My Favorite Convertible Car Seats

• Let Us Help You Pick Your Next Car Seat

👀 Looking Ahead

• New textures and chunkier foods: Your baby might be ready for more complex textures at mealtime. Next week, we'll talk about how to introduce chunkier foods safely, the difference between gagging and choking and what textures are developmentally appropriate right now.