We surveyed 1, 312 pregnant women who were puerperal in-patients of this clinic by retrospective investigation for the effect of hot-spring bathing on the birth weights of babies they delivered.
The women were classified into eight groups.
Group 1 consisted of 14 pregnant women who took hot-spring baths every day and delivered male babies. Group 2 consisted of 115 pregnant women who took plain-water baths with additives every day and delivered male babies. Group 3 consisted of 139 pregnant women who took plain-water baths without additives every day and delivered male babies. Group 4 consisted of 16 pregnant women who took showers every day and delivered male babies. Group 5 consisted of 17 pregnant women who took hot-spring baths every day and delivered female babies. Group 6 consisted of 133 pregnant women who took plain-water baths with additives every day and delivered female babies. Group 7 consisted of 136 pregnant women who took plain-water baths without additives every day and delivered female babies. Group 8 consisted of 17 pregnant women who took showers every day and delivered female babies.
The weights of male babies were 3069.8±357.1g in group 1, 3139.3±396.0g in group 2, 3147.8±382.8g in group 3, and 3037.4±363.7g in group 4. The weights of female babies were 2966.2±337.9g g in group 5, 3050.7±390.6g in group 6, 3087.2±353.1g in group 7, and 3047.9±295.6g in group 8.
The weights of male babies were proportional to the duration of bathing. The weights of female babies were also proportional to the duration of bathing.
The weights of the placentas of male babies were not proportional to the duration of bathing. The weights of the placentas of female babies were proportional to the duration of bathing.
The ratio of the weights of male babies to the weights of the placentas was proportional to the duration of bathing. The ratio of the weights of female babies to the weights of the placentas was not proportional to the duration of bathing.
The conclusion: The above results demonstrate that pregnant women may take hot-springs baths without any adverse effect on the baby.

We studied the effect of hot-spring bathing by pregnant women on the Apgar score of their vaginally delivered babies by retrospective investigation.
The subjects were classified into four groups: group 1 consisting of 33 pregnant women who took hot-spring baths everyday, group 2 consisting of 166 pregnant women who took plain-water baths with additives everyday, group 3 consisting of 308 pregnant women took plain-water baths without additives everyday, and group 4 consisting of 34 pregnant women who showers everyday.
In group 1, the Apgar score was 9 for 27 babies (81.8%) and 8 for six babies (18.2%). In group 2, the Apgar score was 10 for two babies (1.2%), 9 for 125 babies (76.2%), 8 for 37 babies (22.6%), 7 for one baby (0.6%), and 6 for one baby (0.6%). In group 3, the Apgar score was 10 for five babies (1.6%), 9 for 227 babies (73.7%), 8 for 69 babies (22.4%), 7 for four babies (1.3%), 6 for one baby (0.3%), 4 for one baby (0.3%), and 3 for one baby (0.3%). In group 4, the Apgar score was 9 for 30 babies (88.2%) and 8 for four babies (11.8%).
No significant correlations were observed between the Apgar score and the groups who bathed in different ways (hot-spring bathing, plain-water bathing, or showers).
In conclusion, pregnant women can bathe in hot springs without fear of affecting their babies.

We investigated the influences of hot-spring bathing on the incidences of abortion and premature birth using questionnaires returned from 768 puerperal in-patients.
These patients were classified into four groups: 24 taking a hot-spring bath daily (group 1), 134 taking a bath with additives (group 2), 178 taking a plain water bath daily (group 3), and 35 taking a shower daily (group 4).
The incidence of threatened abortion among the ambulatory patients in each group was 4.2% for group 1, 11.9% for group 2, 9% for group 3, and 2.9% for group 4.
The incidence of threatened abortion among the hospitalized patients in each group was 4.2% for group 1, 6.7% for group 2, 4.5% for group 3, and 8.6% for group 4.
The incidence of threatened premature birth among the ambulatory patients in each group was 12.5% for group 1, 17.2% for group 2, 15.7% for group 3, and 14.3% for group 4.
The incidence of threatened premature birth among the hospitalized patients in each group was 0% for group 1, 7.5% for group 2, 3.4% for group 3, and 2.9% for group 4.
The incidence of vaginitis among the patients in each group was 50% for group 1, 43.4% for group 2, 46.6% for group 3, and 44.1% for group 4.
The incidence of premature rupture of membrane (PROM) among the patients in each group was 4.2% for group 1, 21.1% for group 2, 12.9% for group 3, and 22.9% for group 4.
The incidence of premature birth among the patients in each group was 0% for group 1, 3% for group 2, 2.8% for group 3, and 2.9% for group 4.
Among the 42 multiparas experiencing single delivery and being treated for threatened abortion, those who for more than 10 minutes daily showed a significant difference from ambulatory patients being treated for threatened abortion that required hospitalization.
Many of the 63 primiparas who did not use a labor accelerating medicine but bathed for more than 10 minutes daily delivered their babies within 1000 minutes.
Conclusion
The above suggests that pregnant women may bathe in hot-springs without problem but bathing for less than 10 minutes is recommended during early stage of pregnancy.