9.3 Prenatal diagnostics

Symphysis-fundus uteri distance

Since in the last trimenon no ultrasound examination is routinely used, when some sort of growth disturbance is suspected, the diagnosis must be made with the aid of clinical means and these must be performed at the right time. The measurement of the symphysis-fundus uteri distance (SFD) according to Westin has proved to be the best clinical standard (4). This extent approximates the crown-rump length of the fetus.

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Growth disturbances:
Medline plus health information.

For this reason, during the examination in the second trimenon, the SFD is determined when the second ultrasound examination is made and recorded on the standard curve. At each further pregnancy check-up, the SFD is documented in the same way. If it clearly deviates from the percentile band, this can be interpreted as a sign of a fetal growth disorder. In such cases a supplementary ultrasound examination in the 3rd trimenon for adjudging the fetal growth is indicated. Fig. 11 - Symphysis-fundus distance

Fig. 11
The size of the fundus uteri in the various weeks of pregnancy after the LMP.

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The following guidelines concerning the size of the fundus uteri apply:

  • 16th week: 3 finger-widths over the symphysis
  • 20th week: 3 finger-widths below the navel
  • 24th week: at the navel level
  • 28th week: 3 finger-widths over the navel
  • 32nd week: between the navel and the processus xyphoideus
  • 36th week: at the costal arch
  • 40th week: 1-2 finger-widths below the costal arch

The lowering of the fundus uteri is a result of the slackening of the cervix uteri and the consequent descent of the head further down into the small pelvic cavity.


Quiz 08

Cardiotocogram (CTG)

During birth a continuous observation of the child is attempted in order to recognize a danger to the child at the right time. The cardiotocogram is an ideal method for this and consists in a continuous derivation and recording of the fetal heartbeat frequency together with the contraction activity of the uterus during the delivery. In this way, an intrauterine hypoxia can be detected early.

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