How is gestational age and the fundal height related on abdominal examination?

From ~12 weeks the uterus becomes palpable abdominally. Landmarks: at 12 weeks the fundus is at the symphysis pubis, at 20 weeks at the umbilicus, and at ~36 weeks at the xiphisternum.

From ~20-36 weeks the symphysis-fundal height in centimetres roughly equals the gestation in weeks (+/- 2-3 cm) - a discrepancy prompts ultrasound for growth, liquor, multiples or wrong dates.

Clinical relevance. Fundal height landmarks and the SFH rule give a quick bedside estimate of gestation/growth, with discrepancies prompting ultrasound.

More Detail

Fundal height and gestational age

The symphysis-fundal height is a simple bedside estimate of uterine size/gestation.

Landmarks

• 12 weeks - fundus at the symphysis pubis (just palpable).
• 16 weeks - midway between symphysis and umbilicus.
• 20 weeks - at the umbilicus.
• 36 weeks - at the xiphisternum (highest).
• Near term the fundus may drop slightly as the head engages.

Symphysis-fundal height (SFH)

• From ~20 to 36 weeks, the SFH in centimetres roughly equals the gestation in weeks (within ~2-3 cm).
• Measured from the symphysis pubis to the top of the fundus.

Discrepancy

• Large-for-dates (SFH too big) -> polyhydramnios, macrosomia, multiple pregnancy, fibroids, or wrong dates.
• Small-for-dates (SFH too small) -> FGR, oligohydramnios, transverse lie, or wrong dates.
• A discrepancy prompts ultrasound (biometry, liquor, fetal number, dating).