Am curious if anyone has any data on the risks of going from sea level
to high altitude exposure (either flying on an airplane or travel to
the mountains) while pregnant..does it cause vaginal bleeding or
increase risk of preterm labor.

Hi, 

I ran into something while doing the research for this, which I hardly
expected. The main worry I found for high altitude flights was Solar
Flare Activity. I thought this was a bit extreme so I checked out the
NASA website to see if they had something on this, and they did.
Apparently it is a small concern but not one that is as extream as
some of the other websites were making it out to be. Just in case
though, you can check to see if there is Solar Flare activity at the
website I listed below.

According to both the Center for Disease Control and David Shlim
(1997) at
http://www.ciwec-clinic.com/altitude/alti4.html , 
“there are no reported cases of high altitude exerting a negative
outcome on pregnancy in a trekker or climber. Oxygen saturation is
fairly well maintained up to an altitude of 10,000-12,000 feet…Because
of the rapid drop-off in oxygenation above 12,000 feet (3,658 m) or
so, we generally recommend that pregnant women avoid exposures above
that height. However, there are numerous anecdotal stories of women
who have traveled higher while pregnant and who gave birth to normal
children. “

The rest of the articles I found suggested basically the same thing.
Make sure the cabins are pressurized one article said, and that seems
reasonable to me. But none of them suggested anything like the
problems you are asking about, being caused by change of altitude or
air travel. Hope you have a good trip!


Air Travel in Pregnancy
http://pregnancy.about.com/library/weekly/aa052299.htm

Birthnet 
http://www.birth.com.au/class.asp?class=6720&page=1

NASA re: Flying during Solar Flares
http://helios.gsfc.nasa.gov/qa_sw.html#flight

Pregnancy and Altitude
http://www.bodyresults.com/E2pregnantalt.asp

Solar Flare Activity

SpaceWeather.com
http://www.spaceweather.com/


Queries Used
+"while pregnant" +"High Altitude " 
+"while pregnant" +"High Altitude Change" 
+"Flying while pregnant" 
Flying while pregnant vaginal bleeding or increase risk of preterm
labor


Thanks,

webadept-ga

Having flown while pregnant, and with my doctor's approval, I can tell
you that there are some things to watch for, but none of them are
risky:

--increased bladder pressure on take-off and landing.  Visit the
little girls' room just before preparations for these.

--a little nausea until you reach cruising altitude.  Nothing awful,
but you might want to keep a couple saltines in your purse.

--"airplane butt":  that uncomfortable sensation that your behind is
permanently fixed to your seat.  Fix that (and make your legs happy,
too) by walking around periodically.

Typically, the reason most pregnant women are forbidden to fly is
because after about 32 weeks, you can expect Junior to arrive at any
time, with little to no warning, and laboring in flight is not exactly
the ideal situation for anyone involved.  If you're pregnant and
planning to travel, do check with your doctor first and get his
A-okee-dokee before booking a flight.

Good luck!

--Missy

Actually, several authoritative sources *do* cite the possibility of
risk with high altitude, with the risk going up with both length of
high-altitude exposure as well as the hight above sea-level.

Commercial airline flights aren't an issue, as the cabin remains
pressurized. The issues primarily surround 1.) hiking or other
moderate to high-areobic activity, as well as 2.) prolonged exposure
to high altitude. The issue is that  of the possibility of reduced
oxegen to both the mother and fetus.

A good source of information for pregnant women considering trekking
at  a high altitude is provided at:
http://www.ciwec-clinic.com/articles/pregnant.html by the CIWEC Clinic
Travel Medicine Center.

On exposure to altitude:

“Long term exposure to altitude while pregnant has been shown to
retard fetal growth and it has been acknowledged that women tend to
give birth to small babies if they spend much of their pregnancy at
altitude. Small babies have their own set of problems at birth such as
hypothermia, low blood sugar and a higher rate of breathing problems
and a need for intervention. This is more a problem of longer-term
exposure to altitude and it is difficult to predict the effect of a
short visit to altitude when pregnant. It seems probable that a
two-week visit to moderate altitude (less than 3,000 meters) is
unlikely to affect the final birth weight of a baby.”

On acclimatization:

“Acclimatization to altitude can occur during pregnancy; it is not
possible to predict how well an individual, pregnant or not, will
respond to altitude. Most pregnancies show good exercise tolerance at
altitude, but problems such as bleeding and pre-term labor have been
noted to be the most common complications of pregnancy at altitude.
The risk of one of these complications has been shown to increase with
strenuous exercise, dehydration and rapid ascent without
acclimatization. Exercise without full acclimatization (as can occur
during a trek) has also been shown to impair fetal oxygenation.”

Another authoritive (but known for being somewhat alarmist) well-known
pregnancy guide, "What to expect when you are expecting" by Arlene
Eisenberg et. al.  has this to say about high altitude and pregnancy,

"Travel to areas at high altitude may be dangerousm since adjusting to
the decrease in oxygen may be too taxing for both mother and fetus. If
you must make such a trip, you should plan on limiting exertion for
serveral days after arrival to minimize the risk of developing acute
mountain sickness (AMS). If you are in your final trimester, your
doctor may recommend you have a nonstress test on arrival at your
destination and then daily for the next two to three days, and then
semi-weekly"

Search terms used: high-altitude pregnancy risk

Hope this helps!
pkp-ga