Fundal height

Fundal height, or McDonald's rule, is a measure of the size of the uterus used to assess fetal growth and development during pregnancy. It is measured from the top of the mother's uterus to the top of the mother's pubic symphysis. Fundal height, when expressed in centimeters, roughly corresponds to gestational age in weeks between 16 and 36 weeks for a vertex fetus. When a tape measure is unavailable, finger widths are used to estimate centimeter (week) distances from a corresponding anatomical landmark. However, landmark distances from the pubic symphysis are highly variable depending on body type. In clinical practice, recording the actual fundal height measurement from the palpable top of the uterus to the superior edge of the pubic symphysis is standard practice beginning around 20 weeks gestation.

Most caregivers will record their patient's fundal height on every prenatal visit. Measuring the fundal height can be an indicator of proper fetal growth[1] and amniotic fluid development.

Knowledge of gestational age may impact how the height is measured.[2]

Fundal height landmarks

Gestational ageFundal height landmark
12-14 weeksPubic symphysis
20-22 weeksUmbilicus
36-40 weeksXiphoid process of sternum
37–40 weeksRegression of fundal height between 36–32 cm

Shorter measure

A shorter measure can happen for one of the following reasons:

Longer measure

On the other side, a longer measure can be caused by:

As a pregnancy approaches its end, the fundal height will become less accurate.

References

  1. Morse K, Williams A, Gardosi J (December 2009). "Fetal growth screening by fundal height measurement". Best Pract Res Clin Obstet Gynaecol. 23 (6): 809–18. doi:10.1016/j.bpobgyn.2009.09.004. PMID 19914874.
  2. Jelks A, Cifuentes R, Ross MG (October 2007). "Clinician bias in fundal height measurement". Obstet Gynecol. 110 (4): 892–9. doi:10.1097/01.AOG.0000282758.28533.d9. PMID 17906025.
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