Pregnancy and sauna

Pregnancy and sauna is approached in this encyclopaedia the way the obstetric literature approaches it: with respect for the physiology of the developing child, confidence in the Finnish experience of bathing mothers, and a firm boundary that the advice of the midwife or obstetrician decides the individual case. The evidence base is small, the concerns concentrate in early pregnancy and in overheating, and the practical differences between the occasional recreational session of a healthy woman and the "hyperthermia" of the malformation literature are substantial enough that the two must never be conflated.

The concerns

Two distinct questions occupy the literature. The first is whether maternal heat exposure in very early pregnancy — the weeks of organ formation — can harm the developing embryo; this concern comes from animal studies and from epidemiological work on febrile illness and on recreational hot-water exposure such as hot tubs, which reported associations with malformations or loss in some studies and not others. The debate reached the Finnish sauna in the early 1990s through correspondence in the European Journal of Epidemiology, where researchers comparing the hot-tub experience with the deep cultural sauna habit of Finland noted how rarely the Finnish data show associations in a population where sauna use in pregnancy is common — a difference that underlines how dose, duration and the exposure itself matter, and how the "one simple answer" of the wellness literature does not survive contact with the actual studies. The second question is the late-pregnancy one: whether short heat exposures alter uterine activity or fetal well-being. This has been measured directly in at least one Finnish study, which monitored uterine contractility, fetal heart rate and fetal movements during short-term heat stress in late pregnancy; it remains a small field, and the general obstetric view treats the well-hydrated bather in a short session differently from the overheated one.

The physiology for the mother

The mother's own side of the session is the same physiology this encyclopaedia describes everywhere, with pregnancy-specific modifiers. Blood volume and cardiovascular load are already raised, the heart rate and skin circulation respond eagerly to heat (Heart rate in a sauna, Vasodilation), blood pressure is often lower in the middle of pregnancy with the orthostatic dips of the hot room amplified — the standing-up faint of the second and third trimesters is a classic. The general Dehydration and Electrolyte balance rules apply with extra force, because the fluid needs of the pregnancy are layered onto those of sweating; and the comfort rules of the mid-trimester breast and skin sensitivities echo the Skin and sauna and Eczema and sauna pages. Long or repeated overheating — the sustained high core temperature of extended sessions or of added fever (see Fever and sauna) — is precisely what all the guidelines advise the pregnant woman to avoid; short, comfortable, hydrated sessions in a moderate cabin are a different quantity from that.

Practical guidance

The practical synthesis used in facility practice and obstetric counselling: the hot room is optional during pregnancy, and every woman reserves the right to skip it. Those who bathe should keep sessions short and cool-to-moderate (Sauna session duration), drink water before and during (Hydration during sauna), sit near the door with a towel, stand up slowly, never bathe alone (see Going to a sauna alone), and leave at the first sign of dizziness, nausea or headache (Fainting in a sauna, Heat exhaustion, Overheating prevention). In the first trimester, the cautious obstetric reading is to limit heat exposures until the questions of the early-pregnancy literature are discussed with the caregiver; in later pregnancy, the same rules of comfort and hydration apply, with attention to the added burden of the growing uterus on Blood circulation. None of this is a prohibition; the Sauna during pregnancy article gives the specific detail, and the general caveat of the whole subject is the one sentence that belongs in every pregnancy-sauna discussion: the pregnant woman's midwife or obstetrician is the authority, and the encyclopaedia's role is to summarise the science, not to override prenatal care (see Medical advice before sauna and Sauna contraindications).

The balance

The balance of the literature, fairly stated, is reassuring at the level of ordinary, careful use — the Finnish bathing culture has not produced evidence of harm from normal sauna habits in pregnancy, and the direct measurements of late pregnancy show how a short heat episode can be well supported — while remaining emphatic that sustained overheating, dehydration and the collapse of the first faint are obstetric warnings, not folklore. For the partner's side of the question, see Male fertility and sauna; for the children's side, Children and sauna and Sauna with children.

See also

• Sauna during pregnancy
• Medical advice before sauna
• Hydration during sauna
• Heat stress
• Sauna contraindications

References

• Lipson AH, Edwards MJ. "Maternal sauna and hyperthermia during pregnancy and cardiovascular and other malformations in offspring." European Journal of Epidemiology 9, correspondence, 1993. doi:10.1007/bf00211447
• Tikkanen J, Heinonen OP. "Maternal sauna and hyperthermia during pregnancy and cardiovascular and other malformations in offspring (reply)." European Journal of Epidemiology 9, correspondence, 1993. doi:10.1007/bf00211448
• Vähä-Eskeli K, Erkkola R. "The effect of short-term heat stress on uterine contractility, fetal heart rate and fetal movements at late pregnancy." European Journal of Obstetrics & Gynecology and Reproductive Biology 38(1):9–14, 1991. doi:10.1016/0028-2243(91)90200-5
• Kukkonen-Harjula K, Kauppinen K. "Health effects and risks of sauna bathing." International Journal of Circumpolar Health 65(3):195–205, 2006. doi:10.3402/ijch.v65i3.18102
• Heinonen I, Laukkanen JA. "Effects of heat and cold on health, with special reference to Finnish sauna bathing." American Journal of Physiology – Regulatory, Integrative and Comparative Physiology 314(5):R629–R638, 2018. doi:10.1152/ajpregu.00115.2017
• Hussain J, Cohen M. "Clinical effects of regular dry sauna bathing: a systematic review." Evidence-Based Complementary and Alternative Medicine 2018:1857413, 2018. doi:10.1155/2018/1857413