Assess Fundal Height
Fundal height in centimeters typically mirrors gestational age in weeks between 20 and 36 weeks. Deviations greater than ±2 cm warrant evaluation.
How to Use This Calculator
Measure fundal height correctly
Use a measuring tape from the pubic symphysis to the uterine fundus with patient lying supine and bladder emptied.
Enter accurate gestational dating
Use the obstetric gestational age confirmed by early ultrasound whenever possible.
Interpret deviations carefully
Persistent size-date discrepancy warrants further evaluation with ultrasound or maternal assessments.
Formula
Expected fundal height (cm) ≈ gestational weeks (valid between 16 and 40 weeks)
Acceptable range = Expected ± 2 cm
Large deviations can reflect fetal growth restriction, macrosomia, polyhydramnios, oligohydramnios, fibroids, or incorrect dating.
Full Description
Fundal height monitoring is a low-cost screening tool for fetal growth. After 20 weeks, the measurement in centimeters typically matches the gestational age in weeks. Factors like maternal BMI, bladder fullness, fetal position, multiple gestation, or leiomyomas can alter accuracy. Persistent deviations prompt formal assessment via obstetric ultrasound to evaluate fetal anatomy, growth, and amniotic fluid levels.
Frequently Asked Questions
Why is fundal height less reliable before 16 weeks?
The uterus is still within the pelvis, making tape measurements inconsistent; ultrasound is preferred early in pregnancy.
What if the patient is very tall or short?
Maternal habitus can shift measurements. Track trends over time and combine with other clinical findings.
Can fetal position affect the reading?
Yes. Breech or transverse presentations can alter the measurement. Repeat after repositioning if needed.
When should I obtain an ultrasound?
Any sustained discrepancy >2 cm, rapid growth changes, or high-risk pregnancies merit ultrasound evaluation.