My post is not about breastfeeding, it is about the technology currently
being discussed on Lactnet as it may impact breastfeeding.  Personally I
don't think that's very likely.

This topic has actually been examined in obstetrics at least a decade ago.
The amount of energy absorbed by the fetus during a scan with a modern
machine is very very small.  Ultrasound machines spend about one thousandth
of the time sending waves out, and nine hundred ninety nine thousandths of
the time listening for the echoes of those waves.  This means that in a ten
minute scan, there is just over half a second of exposure to ultrasound
waves.  One one-thousandth of six hundred seconds, is six tenths of a
second.  This energy is distributed throughout the area examined, placenta,
umbilical cord, and all the tissues of the fetus.

Cardiotocography, or electronic fetal heart monitoring, OTOH, involves
almost continuous bombardment with ultrasound waves, as it is based on the
Doppler priniciple which differs from the principle underlying diagnostic
imaging ultrasound.  Hand-held electronic stethoscopes for auscultating the
fetal heart during pregnancy use the Doppler principle as well, so there is
reason to use plain acoustic methods for auscultation instead.  Proponents
of extensive use of electronic monitoring of the fetal heart argue that
while the amount of energy is much much greater than with imaging ultrasound
done in the first and second trimesters, the exposure is during labor when
the fetus is as mature as it will ever be before birth.

I am not a proponent of the routine use of cardiotocography in pregnancy or
labor, nor of the routine ultrasound scanning of pregnant women.  I have
lost a job in part because of my critical stance on ultrasound.  I'll be
ready to hear more definitive arguments about the safety or danger of both
these technologies when the daughters born to scanned and monitored women
have had enough children of their own for us to detect changes in
reproductive performance.  For now, the best evidence suggests that the
appropriate strategy is conservative use of both techniques, always on
indication, when the information gained will have an impact on treatment
decisions.  There are plenty of well documented reasons for this stance, in
particular the cost to benefit ratio.  We shouldn't need to scare women for
what to my mind seems a groundless fear of CNS damage resulting from an
indicated scan in early pregnancy, any more than we should persuade them to
have scans they don't need, which is the more common scenario where I live.

Rachel Myr
Kristiansand, Norway
Norway leads the world in rate of scanning pregnant women, not something I
am proud of!

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