Pregnancy has been removed from the list of contraindications for hot spring bathing. Therefore, The Japanese Society of Balneology, Climatology and Physical Medicine has considered that it is necessary to conduct a joint research on the safety of hot spring bathing for pregnant women, publish the results extensively, and enlighten the public about this matter. Considering that only a small number of reports have been published in Japan about the safety of hot spring bathing for pregnant women, the Society has decided to study this subject.   Expectant and nursing mothers living in hot spring towns, such as Beppu and Ibusuki City, have responded to questions about the period between the early stages of pregnancy and delivery via a self-administered questionnaire; The questions included: 1) age when the pregnancy ended, 2) number of previous deliveries, 3) details of hot spring bathing　habits (whether they bathed in hot springs on a daily basis, how often they bathed during the different [early, middle, and late] stages of pregnancy, and whether they used hot spring baths attached to their homes or hot spring facilities away from their homes), and 4) whether they had pregnancy complications such as miscarriages (excluding those occurring in the early stages of pregnancy), premature delivery, threatened premature delivery, or toxemia of pregnancy/pregnancy-induced hypertension (edema, hypertension).  Total 1,721 responses were collected (86% reply rate). The mean participant age was 30.8 years. Importantly, there were 643 (37.6%) primigravid and 1,078 (62.4%) parous women. Age and gravidity were not associated with pregnancy complications. In the early and middle stages of pregnancy, there were no significant differences in the incidence of pregnancy complications between individuals who bathed ≥ once per week [hot spring bath (+)] group and those who bathed < once per week [hot spring bath (−)] group. In the late stages of pregnancy, the number of pregnancy complications were fewer in the hot spring bath (+) group (20.3%) than that in the hot spring bath (−) group (25.9%) (p = 0.028). In addition, there were no significant differences in the pregnancy complications between hot spring bathing (+) and hot spring bath (−) groups in the early and middle stages of pregnancy even if we focused on the homecoming pregnant women. Whereas, in the late stages of pregnancy, the number of pregnancy complications were fewer in the hot spring bath (+) group (13.0%) compared with the hot spring bath (−) group (24.5%) (p = 0.028) in the homecoming pregnant women.  This study has confirmed that daily hot spring bathing during pregnancy does not increase the incidence of pregnancy complications. Furthermore, it can be stated that the removal of “pregnancy” from the contraindications of hot spring bathing was appropriate.