There are several risks of allowing an infant to sleep in a car seat without adult supervision or allowing him/her to do so excessively (e.g., a 3 hour nap vs. 20 min after falling asleep in the car).
The first risk you covered - strangulation. As far as I know, every child seat manufacturer states that you should not leave a child unattended in an infant seat, and several times a year, I read news stories about a baby who is strangled to death after being left to nap or sleep in an infant seat.
There's also a risk that the child could fall out of the seat and/or that the seat could fall off of a table, bed, etc. Again, many babies are injurred each year from this type of fall.
Some very young babies, especially those born early, may have difficulty breathing when reclined in an infant seat for an extended period of time. Some hospitals do testing before sending babies home, but even a baby who passes the hospital's test may experience hypoxia when left in the seat for an extended period, such as overnight.
Finally, excessive use of an infant seat and other such devices outside of the car can lead to positional Plagiocephaly.
While there has been an increase in flatheads recently
reported in North America, New Zealand and Australia there
has never been a concern among countries which traditionally
practice back sleeping. This suggests that other infant care
practices may also play a role in the development of
flatheads. In North America, infants are more likely to be
carried in a back-lying position using a car seat, stroller
or carriage, swings or infant seat during wake and sleep
periods while many other cultures promote more adult/infant
contact through the use of carriers which hold an infant
upright (Nelson 2000).
( http://www.sidscanada.org/research_reducingrisk.html this
link is no longer valid, but I have e-mailed them asking if
the article is still available somewhere else)
But what about the cumulative effect of all these mechanical
assistants [stroller, car seat, crib, infant seat, etc.]? A
rather alarming news item in the January 1998 Brown
University Child and Adolescent Behavior Letter reported an
increased incidence of "deformational plagiocephaly" in
babies, a flattening and distortion of the skull that results
when a baby continually rests his head in one position. The
newsletter notes that not only do babies now usually sleep on
their backs, but "infant carriers [i.e. seats], car seats and
infant swings all require a semi-reclined supine/sit
posture." While the report describes this admittedly rare
condition at some length, it doesn't raise an equally
important concern: When a baby spends most of her day (and
night) in what is essentially a glorified box, isn't she
missing out on something vital - the warmth, touch, rhythm
and smell of her parents and caregivers?
( http://www.todaysparent.com/baby/behaviordevelopment/article.jsp?content=105 )
"Finally, try to be aware of how much time your baby spends
in a car seat, stroller, infant carrier, bouncy seat, or
infant swing where he may be leaning back and putting
pressure on his flat spot. Make sure you take him out of
these devices for a good part of each day and hold him or
play with him on his tummy instead."
(http://www.babycenter.com/expert/1187992.html and
http://www.babycenter.com/refcap/baby/babyills/1187981.html)
"Ways to prevent plagiocephaly I wish I had know about earlier...
...Limit the time your child spends in car seat, swing,
bouncy seat, stroller, and in the infant carrier every day."
( http://www.geocities.com/alittleone2000/plagiopage.htm )
If you have a baby with reflux (GERD), it may be necessary for him/her to sleep with his/her head elevated all the time. During the day, a sling or pack carrier can work well. At night, it is better elevate one end of a child-safe mattress, either in a crib or an appropriate family bed, to achieve the incline. Foam wedges are sold for that purpose. GERD support groups are a good source for information about the latest (safer) recommendations in that situation, and may be more up to date than many physicians.
--
Ulrike
Edited 6/9/2003 6:32:02 AM ET by ulrikedg
