Fetuses are only human. Just like us, they have “up” days, when they feel like kicking up their heels (and elbows and knees), and “down” days, when they’d rather lie back and take it easy. Most often, their activity is related to what you’ve been doing. Like babies out of the womb, fetuses are lulled by rocking. So when you’re on the go all day, your baby is likely to be pacified by the rhythm of your routine, and you’re likely not to notice much kicking—partly because baby’s slowed down, partly because you’re so busy. As soon as you slow down or relax, he or she is bound to start acting up (a pattern babies, unfortunately, tend to continue even after they’re born). That’s why you’re more apt to feel fetal movement in bed at night or when you’re resting during the day.
Activity may also increase after you’ve had a meal or snack, perhaps in reaction to the surge of sugar in your blood. You may also notice increased fetal activity when you’re excited or nervous—about to give a presentation, for example—possibly because the baby is stimulated by your adrenaline response.
Babies are actually most active between weeks 24 and 28, when they’re small enough to belly dance, somersault, kick-box, and do a full aerobic step class in their roomy uterine home. But their movements are erratic and usually brief, so they aren’t always felt by a busy mother-to-be, even though they are visible on ultrasound. Fetal activity usually becomes more organized and consistent, with more clearly defined periods of rest and activity, between 28 and 32. It’s definitely felt later and less emphatically when there’s an anterior placenta getting in the way.
Don’t be tempted to compare baby movement notes with other pregnant women. Each fetus, like each newborn, has an individual pattern of activity and development. Some seem always active, others mostly quiet. The activity of some fetuses is so regular their moms could set their watches by it; in others there’s no discernible activity pattern at all. As long as there is no radical slowdown or cessation of activity, all variations are normal.
Keeping track of your baby’s kicks isn’t necessary until week 28.