Fundal Height Calculator

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Understanding the Fundal Height Calculator

Our Fundal Height Calculator is a valuable tool for expecting mothers and healthcare professionals alike. It provides accurate estimations based on different types of calculations, such as fundal height percentile, gestational age, and fetal weight. In this post, we’ll explore how to use the calculator and answer common questions about fundal height measurements.

What is Fundal Height?

Fundal height is a measurement used to assess the growth and development of the fetus during pregnancy. It is the distance from the top of the uterus (fundus) to the pubic symphysis (a joint just above the genitalia). This measurement can provide valuable information about fetal health and gestational age.

How to Calculate Fundal Height?

Fundal height can be measured directly, but it can also be calculated using the age of the pregnancy (gestational age) with the following formula:

Median SFH (cm)=5.1333+0.1058×GA2−0.02312×GA2×ln(GA)

where:

• Median SFH: Median symphysis-fundal height in centimeters (cm)
• GA: Gestational age in weeks (e.g., 1 week 1 day = 1.14 weeks)
• ln: Natural logarithm

This formula was established by the INTERGROWTH-21st project.

How to Use the Fundal Height Calculator?

1. Choose the Calculation Type:
   • SFH Percentile: Computes the median fundal height based on gestational age and compares it to the actual measured fundal height.
   • SFH to Gestational Age: Computes gestational age based on a measured fundal height.
   • SFH to Fetal Weight: Calculates baby weight by fundal height.
2. Input Necessary Data:
   • Measured SFH: Distance between the top of the uterus and the pubic bone.
   • GA weeks/days: Gestational age in weeks and days.
3. Get Results: The calculator will provide the estimated values based on the input data.

How to Calculate Gestational Age from Fundal Height?

There are two methods to determine gestational age from fundal height:

1. McDonald’s Rule:
   • At 12 weeks, the uterus’ fundus is located just above the pubic bone.
   • At 20-22 weeks, the fundus is at the belly button.
   • At 36 weeks, the fundus reaches the sternum.
   • After 36 weeks, the uterus begins to lower as the baby prepares for delivery.
2. Formula:
3. GA (weeks)=6.5858−2.7073× square root of SFH​+1.2952× SFH

How to Calculate Baby Weight by Fundal Height?

Fundal height can be an indicator of fetal development and wellbeing. Here’s Johnson’s formula to estimate fetal weight:

Fetal weight (g)=(SFH−Weight−Vertex)×155

where:

• SFH: Symphysis-fundal height in centimeters (cm)
• Weight:
  • Takes the value of 1 if the mother weighs > 91 kg (200 lb).
  • Takes the value of 0 if the mother weighs ≤ 91 kg (200 lb).
• Vertex:
  • Takes the value of 12 if the vertex is above the ischial spine.
  • Takes the value of 11 if the vertex is below the ischial spine.