While there’s nothing inherently dangerous about the seaweed itself or the lovely, serene spa setting, the concern here would be overheating. An elevated body temperature of 101 or higher, especially for long periods of time, puts unborn babies at an increased riskfor neural tube defects. Being cocooned in strands of seaweed could easily raise your core temp above the safety threshold. (For the same reason, pregnant women should limit their hot tub and sauna use.)
So what about those really hot days? If you live somewhere with particularly warm and wet weather, San Diego–based expert David M. Priver, MD, FACOG, assures you that you’re fine. “Women’s bodies were designed to carry babies across all climates and cultures,” he says. Above all, stay hydrated. The Institute of Medicine recommends that pregnant women drink about 10 cups of fluids daily. (Water, juices, coffee, tea and even soft drinks “count,” although it’s wise to steer clear of sugar- and calorie-laden drinks, pregnant or not.) Also, remember that thirst is a sign that you’re already dehydrated, so sip often even if you’re not feeling parched.