Ultrasound Technologies PD1 combi, Operating Instructions Manual

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Fetal heart detection
The PD1 combi / PD1+ combi can be used to detect the beating
fetal heart from approximately the 10th week of gestation, though
this will vary between patients.
Apply a liberal amount of coupling gel to the area just above the
symphysis pubis and position the transducer face flat against the
abdomen. Tilt the transducer slowly until the fetal heart is heard in
the loudspeaker or headset (in early pregnancy the headset helps
to eliminate ambient noise making it easier to detect the weaker
signals).
Later on in pregnancy the best signals are generally found higher
up the abdomen.
Avoid sliding the transducer over the abdomen as this results in an
increase in the background noise and makes it more difficult to
detect the fetal heart sounds.
The PD1 combi / PD1+ combi may be used to locate the position
of the placenta, thus aiding in the early diagnosis of placenta
praevia or eliminating placental site where amniocentesis is to be
performed.
The sound from the placenta is an indistinct swishing, caused by
bloodflow in many vessels. There is no distinct beat pattern to the
sound.
The vessels of the umbilical cord give rise to a higher pitched sound
than the normal fetal heart, with pulsations at the fetal rate.