Fetuses have different levels of activity; some move more than others. Fetal movements occur in periods of activity and rest throughout the day (and night.) According to the University of New Mexico Health Sciences Center, women feel at least 75 percent of fetal movements. Week 28 marks the beginning of the third trimester. Pregnant women are advised to begin making note of the pattern and frequency of their baby's movements during this week and report changes in fetal activity to their prenatal providers.
While some are more active than others, all normally developing fetuses roll over, stretch, kick and thrust their arms during their active periods. Fetuses also move when they are startled. Pregnant women typically detect fetal movement by 20 weeks. Babies are most active during weeks 24 to 28. By week 28, fetal movements become more organized and predictable.
Patterns of Activity
Like babies outside the womb, fetuses develop a pattern of activity, alternating between active sessions and quiet spells. At 28 weeks, babies tend to be more active in the evenings and quieter in the morning. Movement increases in the evening hours and when the mother's blood sugar rises, such as after eating or drinking a sweet beverage. The level of activity is individual to each fetus. Over time, a woman usually notices the times of day when her baby is more active and when he is quiet.
At 28 weeks, health practitioners recommend that women monitor their baby's activity. Choose a time when the baby is normally active, such as after a meal. One way to assess fetal activity is to count the number of movements you feel in one hour. Another method is to find out how long it takes to feel the baby move 10 times. Babies average four to six movements per hour. Perform a kick count at the same time each day to determine the average movements per hour for your baby.
When to Call the Doctor
Fewer than eight to 10 fetal movements within a two-hour time period warrants a call to the obstetrician. Also notify your health care provider if you notice changes in your baby's individual pattern of activity, such as fewer movements per hour than her average. Reduced activity or lack of fetal movements might indicate fetal distress. The doctor might want to perform a non-stress test or ultrasound examination to determine the health of the baby.
- University of New Mexico Health Sciences Center: University Midwifery Associates, 24-36 Week Information
- University of Washington Medicine: Obstetrics, You're Baby's Well-Being
- University of Rochester Medical Center: Fetal Movement Counting
- What to Expect When You're Expecting"; Heidi Murkoff, et al.; 2002