I had my baby at 35 weeks, 5 days — it was so scary at first, but luckily he was absolutely healthy and perfect. He’s now five weeks old, so just about his due date, and I’m so confused by how to handle him and anticipate milestones. Do I do what is recommended for a five-week-old or treat him like a newborn? When do we start tummy time? When does he need to stop being swaddled? Etc., etc., etc. Thank you!—New Mama
With preterm babies, when we think about milestones, you want to use adjusted age. Adjusted age is simply the age your child would be if they had been born at their due date (you can subtract, or use a calculator to do it for you). The expected timing of milestones should be based on this adjusted age, rather than chronological age.
What’s important about this is when you start to worry about milestones. The CDC has guidance about what to expect babies to do at two months, four months, and so on. For a baby who was born two months preterm, these milestones should instead be evaluated at four months and six months. Research has shown that, for motor milestones in particular, this approach makes sense to avoid inappropriately classifying too many preterm infants as delayed when, in reality, they spent some of their gestation time out of the womb.
After about two years, these adjustments tend to be taken less rigidly, although doctors will often still have an eye on the idea of adjusting, especially for babies who were very preterm (which 35 weeks and 5 days is not).
What is a little more confusing here is the question of how to treat a preterm baby. The adjusted-age calculator is intended to help doctors identify babies who might need early intervention for developmental delays. It’s not built to define how to treat babies.
Fortunately, most of the guidelines we have about how to treat babies by age are pretty vague and end up being very particular to the baby. Swaddling is most valuable early on, in the first three months (so perhaps the first four months for you), but some people keep swaddling for many months past that, and others do not do it at all. People start sleep training as early as about three months, or wait until nine months or more. Solid foods start sometime between four and six months but really should reflect a baby being ready to start — sitting independently, holding their head up, showing interest — so that should be the cue, not the chronological age.
Bottom line: On milestones, adjust the age before you even start to worry. On most everything else, observe your baby and follow those signs. And when in doubt, ask your pediatrician.