When should symphysis-fundal height (SFH) measurements be started during pregnancy?

When to Start Symphysis-Fundal Height Measurements in Pregnancy

Symphysis-fundal height (SFH) measurements should be initiated at 24 weeks gestation and continued serially throughout the third trimester at every antenatal visit. 1

Guideline Consensus on Timing

Multiple international guidelines converge on starting SFH measurements in the mid-second trimester:

• United Kingdom guidelines recommend serial fundal height measurements on customized charts starting at 24 weeks gestation 1
• New Zealand guidelines recommend beginning at 26 weeks gestation 1
• Canadian, Irish, United States, and French guidelines recommend serial fundal height measurements from approximately 22-24 weeks onward 1

Rationale for This Timing

The measurement becomes clinically reliable between 16-36 weeks gestation, when the height in centimeters approximately corresponds to gestational age in weeks. 2 However, starting at 24 weeks allows establishment of a baseline growth trajectory before the third trimester when detection of fetal growth restriction becomes most critical. 1

Key physiological landmarks:

• The uterine fundus reaches the umbilicus at approximately 20 weeks gestation 1, 2
• Between 20-32 weeks, the rate of fundal growth is approximately 1 cm per week 3
• The fundus reaches the xiphisternum at 36 weeks gestation 2

Measurement Technique

All guidelines recommend using a tape measure to assess SFH, with 50% of guidelines (3 of 6) specifically recommending plotting measurements on customized growth charts rather than population-based charts. 1

The measurement should be performed at every antenatal visit once initiated. 1

Clinical Triggers for Ultrasound Evaluation

Guidelines recommend ultrasound assessment when:

• Fundal height is <10th centile on customized charts 1
• Fundal height shows slow or static growth (change in measurement <5 mm over 14 days) 1
• Fundal height is >3 cm less than gestational age in weeks (using McDonald rule) 1

Important Caveats

Fundal height measurements are unreliable in certain populations, and ultrasound should be considered instead:

• Women with obesity 1
• Women with fibroid uterus 1
• Women with abdominal distention or increased body mass index 1, 2

Evidence limitations: A Cochrane review found insufficient evidence that SFH measurement improves detection of small-for-gestational-age infants compared to clinical palpation alone, though this reflects the quality of available studies rather than proof of ineffectiveness. 4 Despite limited high-quality evidence, all major international guidelines continue to recommend SFH measurement as an essential screening tool, particularly when combined with standardized training and customized growth charts. 1

Special Consideration: Growth Assessment Protocol

The Growth Assessment Protocol (GAP) in the United Kingdom, which incorporates standardized SFH measurement training and customized growth charts starting at 24 weeks, has been associated with increased detection of small-for-gestational-age babies and reduction in stillbirth. 1 This program is recommended by the National Health Service as part of stillbirth reduction initiatives. 1