At week 31 the baby is now about 3 ¼ pounds and 17-18 inches long. The baby’s eyes are able to track light at week 31. You can play with the baby by moving a flashlight along your tummy and the baby may move with the light. If it doesn’t move, the baby’s eyes will be following it.
The baby will have definite sleep wake cycles at week 31. This can sometimes make moms nervous as there may be times during the day when the baby is not moving much. It is completely normal for the baby to have periods of lots of activity and then periods of less activity. The baby is allowed to sleep. You may notice that there is a pattern or rhythm to this variation in activity. I hear from patients that the baby seems to be sleeping during the day and really active at night. Don’t worry, the pattern you feel while the baby is inside of you is not necessarily the pattern the baby will have when it is born.
There are two main reasons babies seem to move more when you lay down to sleep at night. One is that you are less distracted. The baby may be moving during the day but the distractions of life keep you from feeling the movement. When you lay down to sleep you are no longer distracted and now notice the baby moving. The other reason has to do with motion. As you move around you create a rocking motion that is conducive to sleep. When you lay down the motion stops and the baby wakes up. We certainly observe this in newborn babies. Most parents will tell you that rocking the baby or even putting it in a car seat and taking the baby for a ride will help the baby fall asleep.
If you are concerned there is not enough movement a fetal kick count test can be done. To do this test drink some liquids maybe eat a small snack and lay down somewhere quite. Concentrate on the baby’s movements. You should be able to feel 10 distinct movements in under 2 hours. The movements do not have to be strong or even feel like kicks, any movement counts. If you feel 10 movements in less than 2 hours, you can be reassured that the baby is moving enough. If you do not feel these 10 movements you should contact your doctor or labor and delivery, you may need to be monitored.