Fundal Height Calculator

What Is Symphysis-Fundal Height?

Symphysis-fundal height (SFH) is the distance in centimeters from the pubic symphysis to the top of the uterine fundus. After the first trimester, SFH is used to track fetal growth and estimate gestational age. Measurements are most reliable when the fetus is in vertex presentation and maternal factors that distort the abdomen are noted.

Expected SFH from Gestational Age

Given gestational age between 12 and 42 weeks, the calculator estimates median expected SFH using a published regression model:

$$\text{SFH (cm)} = 5.1333 + 0.1058 \times GA^2 - 0.02312 \times GA^2 \times \ln(GA)$$

Where $GA$ is gestational age in decimal weeks. Pair this with the Gestational Age Calculator when dating pregnancy from last menstrual period or ultrasound, or the Crown-Rump Length Calculator for early pregnancy dating.

Reverse Calculation and Fetal Weight

Measured SFH can be converted back to estimated gestational age using the inverse of the median curve. Fetal weight estimation uses the Johnson formula:

$$\text{Weight (g)} = (\text{SFH} - W - V) \times 155$$

Where $W$ is 1 if maternal weight is above average and 0 otherwise, and $V$ is 12 when the vertex is above the spine or 11 otherwise. SFH that falls far from expected range may prompt ultrasound for growth assessment.