I don't think it is safe even when you aren't pregnant. If you're pumping water into there at any time you can get an infection. If you're in a shower it's different but I don't think it's a good idea in a bath or a pool.
:::Sex in a hot tub, Jacuzzi or pool can lead to infections. During sexual activity, water can get forced into the vagina or anus. This water may be teeming with microbes which can lead to an infection. Sometimes residential (and commercial) hot tubs, pools and Jacuzzis are not chlorinated adequately, increasing the amount of bacteria they contain and the likelihood of an infection. Even if the water in a hot tub has a chlorine level maintained in accordance to government standards, there is still a risk of infection if the water is forced into the vagina or anus. Exposing a vagina to chlorine may disrupt healthy native bacteria and change the natural pH (acidity) in the vagina leading to a yeast infection.:::