As you near the end of your pregnancy, you might notice changes in the movement of your baby. Some mothers notice a change in the frequency or timing of fetal hiccups. In most cases, this isn't a problem; your baby is simply experiencing a normal involuntary reflex. If you have concerns or notice a significant increase in hiccups, you may want to ask your doctor if everything is OK, since this can on rare occasions be an indication of a potential problem.
Almost all pregnant women feel fetal hiccups by the ninth month of pregnancy, and many feel them much earlier. They feel like small, rhythmic movements, and some moms-to-be notice them multiple times a day, while other women feel them only every once in a while. They can last anywhere from a few seconds to 10 or more minutes. You might be more prone to feel them during the last trimester as your due date approaches, because your womb is becoming more cramped and your baby presses up against the wall of your uterus. But the actual frequency of hiccups usually decreases during the last trimester. In addition to feeling your baby's hiccups, you might be able to hear your baby's hiccups on Doppler ultrasound if he has an episode during one of your prenatal visits.
The precise cause of hiccups in the womb remains unknown, but researchers believe it might have something to do with the development of the lungs and could be helping pave the way for breathing in the future. This involuntary movement of the diaphragm could also be a harmless reflex that has nothing to do with the baby's development. There is no association between fetal hiccups and particular behavioral states in the unborn baby, such as the baby having them more frequently when awake or asleep.
While most cases of fetal hiccups are harmless, report any sudden changes in the frequency and amount of hiccups to your doctor. In some cases, fetal hiccups could be a sign of a problem with the baby's umbilical cord, which could be compressed or wrapped around him. Your doctor might want to check your baby's blood flow using ultrasound if you have noticed multiple episodes of hiccups lasting 10 minutes or longer, especially if they are also accompanied by other changes in fetal movement.
If your baby hiccups a lot in the womb, you'll probably notice that he also hiccups frequently once he's born. You might want to keep a diary of when you feel fetal hiccups, both to keep your doctor informed as well as to have a fun record of your baby's activity before birth.