It is not recommended, as your body temperature can go above what is considered safe for your baby.
While soaking in a hot tub might sound like the perfect way for a pregnant woman to relax, it is actually not the best idea. Hot tubs are usually kept around 104 degrees Fahrenheit, and the American College of Obstetricians and Gynecologists recommends that a pregnant woman’s body temperature does not get above 102.2 degrees Fahrenheit.
In the typical hot tub, it would only take about 10 minutes or so of soaking to get above this danger zone. Keeping a cooler temperature is recommended because a high core body temperature, also known as hyperthermia, can lead to miscarriage and predispose a developing baby to certain birth defects in the first trimester. It can also raise the temperature of a developing baby and increase his or her heart rate to a rate that is too fast at any point in the pregnancy.
If you must have a dip, only spend a couple minutes in the hot tub or program it to a cooler temperature. Another alternative is a warm bath, and there is no time limit on how long you can enjoy that!