What does a discrepancy between fundal height and expected gestational age indicate?

From the Guidelines

A discrepancy between fundal height and expected gestational age is a significant indicator of potential pregnancy complications, and when the difference exceeds 2-3 cm, it warrants further evaluation with ultrasound to assess fetal growth, amniotic fluid volume, and fetal anatomy. This discrepancy can suggest various issues, including fetal growth abnormalities, amniotic fluid disorders, or multiple gestation. If the fundal height is larger than expected, possible causes include polyhydramnios, multiple pregnancy, fetal macrosomia, uterine fibroids, or gestational trophoblastic disease 1. Conversely, if the fundal height is smaller than expected, it might indicate intrauterine growth restriction, oligohydramnios, fetal malposition, or incorrect dating of the pregnancy.

Key Considerations

• The definition of fetal growth restriction (FGR) is crucial, with most guidelines recommending an estimated fetal weight or abdominal circumference below the 10th percentile for gestational age 1.
• The use of population-based fetal growth references, such as Hadlock, is recommended for determining fetal weight percentiles 1.
• Regular assessment of fetal biometry, amniotic fluid volume, and fetal well-being through Doppler US and fetal heart rate monitoring is essential for managing pregnancies with suspected FGR 1.
• The cerebroplacental ratio, calculated by dividing the middle cerebral artery pulsatility index by the umbilical artery pulsatility index, has emerged as a predictor of adverse outcomes among fetuses with FGR 1.

Recommendations

• When a discrepancy between fundal height and expected gestational age is found, additional assessment with ultrasound is typically recommended to evaluate fetal growth, amniotic fluid volume, fetal anatomy, and placental position 1.
• Serial umbilical artery Doppler assessment should be performed to assess for deterioration in fetuses with suspected FGR 1.
• Delivery at 37 weeks of gestation is recommended for pregnancies with FGR and an umbilical artery Doppler waveform with decreased diastolic flow but without absent/reversed end-diastolic velocity or with severe FGR with estimated fetal weight less than the third percentile 1.

Clinical Implications

• A discrepancy between fundal height and expected gestational age is not a diagnosis but rather a clinical finding that prompts further investigation to ensure appropriate management of potential pregnancy complications that could affect maternal and fetal outcomes.
• The management of pregnancies with suspected FGR should be individualized based on the specific gestational age, presence of structural defects, chromosomal abnormalities, Doppler abnormalities, fetal well-being, and other sonographic findings 1.

From the Research

Fundal Height and Gestational Age Discrepancy

• A discrepancy between fundal height and expected gestational age can indicate potential issues with fetal growth, such as intrauterine growth restriction (IUGR) 2, 3.
• Fundal height is a measurement used to estimate gestational age, but its accuracy can be affected by various factors, including maternal weight, parity, age, and ethnicity 4.
• Studies have shown that fundal height has a low sensitivity for detecting abnormal intrauterine growth, ranging from 16.6% to 17.3% 4.
• The use of fundal height to estimate gestational age is also inaccurate, with a mean bias of -14.0 days compared to ultrasound-confirmed gestational age 5.

Intrauterine Growth Restriction (IUGR)

• IUGR is a common complication in pregnancy that can increase morbidity and mortality at all stages of life 2, 3.
• The management of IUGR typically involves antenatal biophysical testing and umbilical artery Doppler studies 3.
• A study found that IUGR associated with umbilical Doppler II or III does not show any benefit from expectant management in terms of long-term morbidity 6.

Screening and Diagnosis

• The sensitivity and specificity of fundal height as a screening tool for abnormal intrauterine growth are limited, and other modalities should be considered to screen for growth abnormalities 4.
• A guideline for screening, diagnosis, and management of IUGR recommends using a combination of history, physical examination, laboratory investigations, and ultrasound characteristics to identify affected pregnancies 2.
• Increasing access to quality ultrasonography early in pregnancy can improve gestational age assessment and detection of IUGR 5.