For most dads, feeling their baby kicking for the first time is a significant milestone in many ways. It’s not just their first chance to roughhouse, baby kicks are an emotional experience for new fathers eager to meet their child. And from their growing bones to their tiny hiccups in the womb, there are scientific reasons why babies move, kick, and flutter in utero.
But when do babies start to move? When can moms and dads feel babies kicking? And at what point should they start to worry? It might be too soon to sign your fetus up for soccer practice, but research reveals everything else dads need to know about baby kicks — including how to instigate more of them. Bring it on, kid.
Why Babies Kick in Utero
Fetuses don’t just shift because it’s cramped in there—every sharp kick helps shape your baby’s growing bones. A recent study in the Journal of the Royal Society Interface found that the force of fetal kicks markedly increases between 20 and 30 weeks gestation, and then declines by 35 weeks. This suggests that a baby’s kicks are the most vigorous during those middle stages of fetal development, just when bones and joints are beginning to take shape. It makes sense. Animal studies have shown that stationary fetuses emerge with bone and joint problems; conversely, weight-bearing exercises like brisk walking have been shown to strengthen bones.
Fetal movement may also be linked to long-term behavior. One fascinating, but far less authoritative, study found that “fetal motor activity appears to predict temperament attributes related to regulatory behaviors in early childhood.” So it’s possible that kicking also has something to do with neurological development (although causation is entirely unclear, and it’s also possible that babies with poor neurological development move less in utero).
Regardless, these studies broadly suggest that, when your baby kicks, it’s probably not just a friendly salutation from the inside—it’s an important part of fetal development.
When They Should Kick and When to Worry
Babies start moving at 12 weeks, but mom is unlikely to feel anything besides “flutters” until 16-20 weeks. That’s when you’ll feel your first kick. These kicks should strengthen, with a complement of twitches (those are baby hiccups!), through the third trimester, slowing down slightly around week 36 when the womb becomes too crowded for vigorous thrashing. Babies are most active in the morning and in the evening, and their movements are easiest to detect when the mother is sitting or lying down. Dads, if you want to feel a kick, let mom relax.
Starting at the beginning of the third trimester, physicians generally recommend that parents begin monitoring fetal movements. If at any point a mother suspects the baby is moving less than usual (even after 36 weeks), she should call her doctor immediately. Babies don’t move all the time but, as a rule of thumb, shoot for 10 movements per hour in the third trimester. And keep a careful eye on whatever is normal for your baby. If a child is always bouncing against mom’s belly in the morning, even one morning without fetal movement is cause for concern.
How to Get More Kicks
There are a handful of age-old tricks that ultrasound techs use to get sleepy babies moving in utero. Drinking juice or another sugary beverage is a time-honored way to give your kid a minor sugar rush and, similarly, raising your adrenaline by watching a scary movie can put your fetus on high-alert. In the third trimester, when the baby’s eyes and ears are more or less done cooking, shining a light on mom’s belly or playing music may help your baby perk up and kick.
One recent study found that babies move when their mothers are lying on their sides, and freeze up when mom lies on her back. The reason is a horrifying—mothers decrease their fetuses’ oxygen supply when they lie on their backs in late pregnancy, so their babies stop moving to conserve oxygen. Regardless, the joy (not to mention reassurance) of regular baby kicks is just one more reason for pregnant women to sleep on their sides.