But, that being said, I feel it is my role to bring a little balance back into the universe. I get very angry when I see discussion forums where women discuss what it was that caused their miscarriage, their baby's neural tube defect, etc. There are just endless comments such as this: "I had a fever when I was 3 weeks pregnant and a miscarriage at 6 weeks. People try to tell me that is not what caused it, but I know better...". Come on now. Fevers are common. Miscarriages are common. A woman having a fever and then a miscarriage proves nothing. And bear in mind, women who have a fever and don't develop any problems never write anything. This is how myths develop. The women who write these comments think that they are helping solve the mysteries of the human body. But they are actually doing a huge disservice to other women who become fearful after they develop a fever.
Now for a little personal background: I am a professional sauna sitter.
That is not me in the picture. If it were, I'd be naked like all the other Danes.
Actually, I am not a professional. I just sit in a sauna about 3 times a week. When I got pregnant, I didn't think twice about continuing, granted I can't sit in there nearly as long. I even told my swimming friends about my pregnancy in the sauna. Tons of pregnant women sauna sit in Denmark; it is simply part of the culture here. One day, a woman was telling me a personal story in the sauna and I suddenly got the emergent need to GET OUT. When I got out, I felt terrible in like the primordial terrible kind of way. I almost threw up, but didn't. This was the first time I thought "maybe that wasn't so healthy". But I reassured myself that pregnant women get fevers all the time (with certainly higher core temperatures for longer periods of time) and end up with perfectly healthy babies. If we've evolved through fevers, we must be able to tolerate saunas.
But what does research show?
In 2002 a study was done in Denmark in 24,000 pregnant women demonstrating no relationship between fever and miscarriage or still birth, regardless of how high the fever was or how long it lasted. So one must conclude that if there is an association, it is a very small one because this was an exceptionally large study. (The Lancet, Volume 360, Issue 9345, Pages 1552 - 1556, 16 November 2002 )
What about neural tube defects? Well I will point out first an observational study from Finland where they found that 98.5% of expectant mothers visited the sauna regularly and that Finland has close to if not the lowest percentage of neural tube defects in the world. Now, that is not to say saunas are beneficial, just to say that they are likely not very harmful (Saxén, Sauna and congenital defects, Teratology Volume 25, Issue 3, pages 309–313, June 1982).
So where did all the fear come from? First animal studies. And then a study in the Journal of the American Medical Association in 1992. In a study of nearly 24,000 pregnant women, there was no significant association between any single heat exposure (hot tub, sauna, electric blanket or hot tub) and neural tube defect when they were examined together randomly. BUT there was an association between hot tube use and neural tube defect that was significant. This was NOT true for fevers, electric blankets or saunas. From this, somehow it was deduced that any heat exposure (including that from exercise!) was potentially dangerous to the developing fetus. THIS (and animal studies) is where the "don't overheat during exercise while pregnant" comes from. Read the study for yourself and decide what you think (Mulinsky et al JAMA. 1992 Aug 19;268(7):882-5.). My personal interpretation of this is it tends to be women of a lower socioeconomic class that frequent hot tubs in the US while pregnant and that this group also tends to have poorer nutrition and higher percentages of substance and alcohol abuse. This was not controlled for, likely because they thought the study would not get published if they did not show any significant associations (studies with positive associations are about 9 times more likely to be published).
Bottom line - don't worry about an increase in body temperature from exercise in pregnancy inducing a neural tube defect (neither fevers nor saunas have an association, so why should exercise, which almost always rises the core body temp less?)But watch out for yourself like usual! Heat stroke is always dangerous (but is, by the way, much less likely while pregnant due to improved heat dissipation). I am still uncertain what the significance of the hot tub - neural tube defect is.
But now you can see why I didn't go into Ob-Gyn in the US. Can you imagine the lawsuits?! But on this blog, I feel free to give you all my honest opinion. Heck, when it comes to pregnancy, I am a scardy-cat. But no one needs to worry about things that aren't actually dangerous.
Remember, we are all nomads from Africa genetically - it simply doesn't make sense that an increase in body temperature from exercise would be dangerous.
On HOT SPERM
There has been a little banter going on between Piccola Pinecone and myself about whether or not a female's core body temperature rising slows down sperm transport, thus decreasing fertility. PPC said that she had read this in a Clapp book (does he have more than one?). Anyhow, I have not been able to find this study or any related study for that matter, but I simply want to point out why this theory doesn't make sense to me.
Sperm like to live in relatively cool temperatures. That's why they live outside the body (in the testicles). It is well documented that a rise in temperature in "the balls" causes DNA damage to the sperm and can affect fertility. But certainly once sperm enter the female body (or go into their active state), they have to be "ready" for the increased temperature inside the female body. Otherwise none of us would be here. And if an increase in a woman's body temperature (from for example exercise) negatively impacts the sperm, why is it evolutionarily speaking that we get so warm (as in exercise) during the actual act of baby making?
Okay, that last part was more "something to chew on" :) rather than proof of anything.
Running songs of the day:
Something old - Jesus He Knows Me by Genesis
Something new - Freedom Hangs like Heaven by Iron & Wine