You'll usually feel your baby kicking inside the womb around the fifth month of pregnancy, according to [What to Expect](http://www.whattoexpect.com/pregnancy/ask-heidi/week-21/baby-movements.aspx). Thin women and those who've had previous pregnancies may feel kicking during the fourth month. Kicking is a natural part of pregnancy because your baby needs movement and exercise as part of the developmental process. If you can't feel your baby kicking by your fifth month of pregnancy or the kicking ceases for more than a day, consult your physician to make sure everything is OK.
Stretching, Exercise and Brain Activity
Kicking allows your baby to stretch his legs, torso and hips. The movements encourage muscle development and allow your baby to exercise in the womb. Kicking also encourages electrical activity in the brain, according to a 2006 study by Gyorgy Buzsaki, a professor of neuroscience at Rutgers University, and Rustem Khazipov, a professor at medical research facility INSERM in Marseille, France. This activity helps babies perceive the world around them, including distances between their different body parts, according to Rutgers.
Influx of Nutrients and Exercise
Babies often kick when nutrients enter their blood stream. Shortly after you eat, your baby receives a portion of the consumed nutrients, increasing her energy level. Kicking may be most noticeable after you eat sweet foods or drink extremely cold beverages, according to the American Pregnancy Association. In some cases, babies kick more actively between 9 p.m. and 1 a.m. as a woman's natural sugar levels decline. Babies often respond to physical activity with movement, so your morning walk or workout at the gym could get your baby kicking.
Awake Time and Hiccups
Some babies experience predictable sleep and awake times. Even though they kick during sleep, you might notice more movement when they're awake. During awake times, they like to explore their tight living quarters by rolling around, changing positions and kicking. Babies get hiccups in the womb and may respond with short quick kicks, which is a natural impulse. You'll likely be able to feel -- and possibly even hear -- your baby's hiccups. Hiccups are a natural part of pregnancy, so there's usually no need for alarm, even if they occur frequently.
Reasons to Contact a Physician
Contact a doctor if your baby's kicking becomes painful. You might notice some discomfort, especially during the final trimester as your baby's kicks become more forceful. The kicks could catch you off guard and you might see or feel his foot press or roll against your stomach, but you shouldn't experience any pain. Consult a doctor if you don't feel any kicking by your 25th week of pregnancy or if you feel frequent kicking that suddenly stops for more than a day. Due to your baby's increasing size, you should feel frequent movements -- including kicking -- during most of your third trimester.