Pregnant women often feel a mild spasm or movement of the entire belly, which can actually be fetal hiccups. A fetal hiccup is different from a fetal jerk or kick, which are felt as thumps on a specific area of the belly. Hiccuping in the womb may cause anxiety for pregnant women, but this phenomenon is normal and essential for fetal development. There are very few studies about hiccuping in the womb, and its exact cause has not been yet identified. The various theories that point to the cause of hiccuping in the womb include amniotic fluid, reflex development, and umbilical cord compression.

Hiccuping in the womb may begin late in the first trimester or early in the second. At this stage, the mother usually cannot feel it; she usually won't feel anything until late in the second trimester or early in the third. Fetal hiccups may continue through the end of the pregnancy. Although they cannot be felt in the earliest stages, a Doppler machine can detect the hiccups.

One of the suggested causes of hiccuping in the womb is the amniotic fluid. When amniotic fluid goes into and out of the fetal lungs, the diaphragm contracts and causes fetal hiccups. Fetal hiccups may help in the preparation of the lung functioning for breathing after birth and in the regulation of the fetal heart rate late in the pregnancy.

Some medical professionals suggest the cause of hiccuping in the womb is the reflex development for sucking and swallowing. Sucking ensures that the baby will be properly able to nurse right after birth. Swallowing prevents the baby from aspirating milk into his or her lungs.

Hiccuping in the womb for more than 10 minutes may be associated with umbilical cord compression. Umbilical cord compression is bad for the baby inside the womb because it may cause fetal distress, which may eventually lead to death of the baby inside the womb. For this reason, abnormally persistent fetal hiccups should be reported to a medical professional and closely observed. Doctors usually recommend an ultrasound to confirm cord compression.

Fetal hiccups generally do not cause discomfort, but they may occasionally cause anxiety to pregnant women. There is no way to prevent or stop fetal hiccups, and there is usually nothing to worry about it because it is generally normal. If the hiccups persist or the pregnant mother becomes very nervous about the sensation or condition, they should be reported to a medical professional and carefully monitored.