Fundal Height Measurement: Evidence‑Based Guidelines for Detecting Discrepancies

1. Primary Factors Contributing to Fundal Height Discrepancy

Fundal height (SFH) discrepancies stem from both true fetal growth abnormalities and technical/maternal measurement confounders, the most common being maternal BMI > 35 kg/m², abnormal fetal lie, large uterine fibroids, polyhydramnios, and fetal head engagement. 1

Polyhydramnios of any etiology (e.g., fetal anomalies, maternal diabetes, twin‑twin transfusion) leads to an increased SFH. 1

Maternal BMI > 35 kg/m² at booking makes SFH measurements unreliable and inaccurate. 1

Large uterine fibroids distort SFH measurements, potentially producing falsely high values. 1

Abnormal fetal lie (transverse or oblique presentation) hampers accurate SFH assessment. 1

Fetal head engagement in the pelvis reduces measured SFH, potentially masking growth restriction. 1

Significant intra‑ and inter‑observer variation exists in SFH measurement; however, serial measurements can improve predictive accuracy. 1

2. Indications for Ultrasound Referral

If a single SFH plot falls below the 10th centile, an ultrasound should be performed to evaluate fetal growth. 1

When SFH shows no increase over two measurements taken more than two weeks apart, an ultrasound evaluation is warranted. 1

The urgency of ultrasound referral should be modulated by additional clinical findings such as altered fetal movements or abnormal maternal blood pressure. 1

3. Optimal Timing for Routine SFH Surveillance

Routine SFH monitoring should begin between 26 + 0 and 28 + 6 weeks’ gestation; initiating earlier leads to a high rate of false‑positive referrals. 1

Performing SFH measurements between 24 + 0 and 26 + 7 weeks tends to generate excessive referrals because centile relationships are less stable in early gestation. 1

4. Measurement Technique Recommendations

Measure from the uterine fundus to the symphysis pubis while keeping the tape hidden from the examiner to minimize observer bias. 1

5. Limitations of SFH as a Screening Tool

SFH has poor sensitivity for detecting small‑for‑gestational‑age (SGA) fetuses, though its specificity is moderate; it remains useful for low‑risk pregnancies due to its simplicity and low resource requirement. 1

In women with BMI ≥ 35 kg/m², routine SFH should be avoided and direct ultrasound surveillance employed. 1