Causes of Pulsating Sensations in the Abdomen During Late Pregnancy

The third trimester of pregnancy begins at week 28 and continues until delivery, typically around week 40, encompassing the eighth, ninth, and tenth months of gestation. The sensation of the fetus “jumping” or “pulsing” during this period is most commonly due to fetal movement—i.e., fetal kicks and activity. Fetal movement begins as early as weeks 7–8, but it is too subtle at this stage for the mother to perceive. During the second trimester—when early pregnancy symptoms (e.g., nausea) have largely subsided—fetal movements gradually become noticeable. Under normal circumstances, pregnant women begin to feel fetal movements around weeks 18–20; these may feel like small fish swimming, intestinal gurgling, or more forceful kicks and punches. If no fetal movement is perceived at all, this may indicate abnormal fetal activity.

In addition to fetal movement, the “jumping” sensation may also be caused by fetal hiccups. Fetal hiccups can begin as early as mid-pregnancy but typically become more pronounced in the third trimester. They result from rhythmic contractions of the fetal diaphragm and usually occur at a fixed location with consistent, regular intervals—producing a distinct, rhythmic “bouncing” sensation that the fetus cannot control. Even if mothers cannot distinguish between fetal movement and hiccups, there is no cause for concern: both are entirely normal fetal activities with no adverse effects on the fetus and will continue until birth.