what is the difference between doplar and U/S?

[tzs]

ok....so the deal is that we don't do ultrasounds unless there is a medical reason to do it (not dating, not to see the heartbeat....)
but last pregnancy i realized maybe halfway through that the doplar machine that my OB used (reluctantly, because he thinks U/S is "fun") because i wasn't getting the scans is not only a different form of ultrasound but i think i heard that it uses higher "doses" or whatever the case is.

i tried googling it but i dunno....

does anyone know what the deal is with doplar?

[nicky85]

Here is a link to wikipedia's entry on fetal heart monitors: http://en.wikipedia.org/wiki/Doppler_fetal_monitor

It does use ultrasound waves. It's not something I like, but I figure a minute or two of getting the heartrate is better than 10-30 minutes of all-over exposure from a sonogram. Just getting the heart rate also means that you don't have to be laying on your back as long like you would for a sonogram, which can reduce blood flow to the baby during the second and third trimesters.

Most Doppler heart monitors use 2-3 megahertz probes, I can't find out much about actual sonogram machines.

PS- I agree with you that it's "the deed not the breed"!

[MaerynPearl]

prenatal sonogram ultrasound is usually 7-18 MHz

while, as was just said, doppler ultrasound is usually 2-3MHz

So sonogram is a higher frequency and longer periods of time.



that said, I don't worry about either myself. All three of my children have had to have several ultrasounds (for various reasons, from dating due to honestly not knowing how far along I was... to an emergency room trip where the ultrasound diagnosed a placental abruption...)

I find there are things I do on a daily basis which are much more likely to damage them. Like sit at a computer. Or use CFL bulbs (honest... look up dirty electricity and CFLs)

[WifeofAnt]

Only a few times have I needed the doppler for more than 5 seconds. Usually my doctor is pretty good about making it super quick. So even if doppler were 'worse' all my added up doppler time won't even come close to the freakin' hour it took the ultrasound tech to finish with our 18w anatomy scan.

[Jodie8]

I've read in multiple places including Anne Frye's "understanding lab work in the childbearing year" that one minute of doppler is equivalent to 35 minutes of sonogram because the doppler emits continuous waves and sonogram emits pulsed waves. Makes sense to me. Here's a link: http://www.ehow.com/about_5347776_da...l-doppler.html

I have more too if you would like.

[tzs]

well, i don't do ultrasounds so much for "crunchy" reasons but rather religious ones. it sounds kooky, i know, it might sound kookier if i tried to explain it. so trust me, there for sure are way worse things i expose my body to...um....massive amounts of diet coke for starters.

basically my OB likes to do them monthly and really he only does it for a minute or two, not an intensive scan like the 20 week one. probably about the same length of time he takes with the doplar.

sounds like i have to look deeper into the reasons behind the religious reasons to figure this one out. hmmmm.....

[MaerynPearl]

Thats ... odd? I wouldn't say kooky though... all religions have their things they aren't totally okay with and their own reasons for them.

But yeah, if ultrasounds not okay with your religion then I would assume that includes doppler

FWIW though, you do have an alternative, using a fetoscope. Which is just a fancy stethoscope pretty much. Of course, it cannot be used until later than the doppler... but many midwives and some doctors know how to use them.

[Just1More]

I get you on the religous reasons. Maybe mine are not yours, but I can relate. (Though I've had u/s and doppler use...) I find the more I learn to ease up on the control factor, and trust and wait...the less I have use for medical wonders.

YES...SIGN ME UP for whatever if I have some serious thing going on (or my baby), but I'm not jumping up and down that a hb check once a month is going to find it. And I learned (the hard way) that u/s is not all it's cracked up to be...with it's high rate of false positives, and low rate of finding true anomalies.

Someone once said to me that babies are "knit in secret"...at least they are supposed to be.

[MamaChef]

That Anne Frye stat irks me...

Colorflow and spectral doppler.. ie, visual doppler/ doppler ultrasound.. not handheld dopplers/ doptones are much more powerful then plain ultrasound.

Colorflow and spectral doppler are high frequency pulsed doppler using a transducer that is anywhere from 3-12Mhz, 3d and 4D US can be up to 2000x more powerful then a doppler...handheld doppler or doptone is a continuous wave at 2 or 3 mhz using a 9 volt battery

Yes, there is ultrasound, but no, the doppler your midwife uses is NOT more powerful then an ultrasound.. much less 20 or 30+ x more powerful.

http://www.naturalchildbirth.org/nat...ventions27.htm

[Vol 2 Issue 9 March 3, 2000]:

Do most midwives regularly make use of the Doptone? Also, shouldn't each
woman be made fully aware that the Doptone is ultrasonic? Even though the
exposure periods are usually brief, I heard that 1 min. of Doptone is much
stronger--equal to 30 min of the other full-image type ultrasound. Is this
true?
Anon.
====

[Vol 2 Issue 10 March 10, 2000]:

...
Second, you stated that the frequency of Doppler devices is higher than an
imager device. This is also not true. The Hitachi unit ... has a
trans-abdominal probe that transmits at 3.5 MHz. The industry standard for
obstetrical Dopplers is either 2 or 3 MHz. Imex in fact sells both. Higher
probe frequencies that we sell such as 5 and 8 MHz are used for vascular
applications and are labeled "Not Designed For Fetal Use."

In addition, I would like to point out that the FDA limit for power
intensity emitted by a continuous wave ultrasound for fetal use is 0.094
watts per square centimeter. The FDA power intensity limit for pulsed wave
ultrasound for fetal use is 190 watts per square centimeter. The power
emitted by a Doppler can be 2,000 times less than an imager! Imex 3 MHz
probes emit 0.009 watts per square centimeter, a factor of ten times less
than the FDA limit.


Reprinted from Midwifery Today E-News (Vol 2 Issue 10 March 10, 2000)

[CinCanada]

Wow great thread! I really appreciate the info everyone. I hadn't realised until a few weeks ago that doppler could be stronger (now it appears that depends on the type & model) than ultrasounds. I asked my mw about it & said that yes it is stronger because it is a more focused ray but shrugged & said it was no biggie if I wanted to avoid it & only use a fetoscope but that she wouldn't be able to hear a hb until after 20 weeks then.
I didn't ask more details than that at the time but was satisfied by the answer.

[nia82]

We're skipping the doppler this time. We only did a 20 week ultrasound to check that everything is fine and we can birth at the birthing center. our midwives use fetoscopes instead if one asks. At my last appointment (22 weeks) they were able to hear baby's heartbeat with the fetoscope, and I have an anterior placenta even.

[nicky85]

MamaChef, thank you for your info! That makes sense to me. =)