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Ear length in trisomy 21 fetuses at 11-14 weeks of gestation
C Sacchini1, A El-Sheikhah, S Cicero
1Harris Birthright Research Centre for Fetal Medicine, King's College Hospital Medical School, London, UK.
Insights
Fetal ear length measurement at 11-14 weeks gestation shows reduced length in trisomy 21 fetuses. However, this difference is too small to be a reliable screening tool for chromosomal defects.
Area of Science:
- Prenatal diagnosis
- Fetal medicine
- Genetics
Background:
- Chromosomal abnormalities, such as trisomy 21, are significant concerns in early pregnancy.
- Accurate screening methods are crucial for timely intervention and management.
Purpose of the Study:
- To evaluate the diagnostic value of fetal ear length measurement in screening for chromosomal defects during the first trimester.
- To assess the correlation between fetal ear length and crown-rump length in normal and trisomy 21 fetuses.
Main Methods:
- Fetal ear length was measured in 450 fetuses between 11-14 weeks gestation prior to chorionic villus sampling.
- Karyotyping was performed to determine fetal chromosomal status.
- Ear length was analyzed in relation to crown-rump length and compared between chromosomally normal and abnormal fetuses.
Main Results:
- Fetal ear length significantly increased with crown-rump length in chromosomally normal fetuses.
- Trisomy 21 fetuses exhibited a significantly reduced median ear length compared to normal fetuses (0.45 mm reduction).
- However, only 6.3% of trisomy 21 cases fell below the 5th centile of normal ear length.
Conclusions:
- While fetal ear length is reduced in trisomy 21 fetuses at 11-14 weeks gestation, the deviation is minimal.
- Fetal ear length measurement alone is not sufficiently sensitive or specific for effective screening of trisomy 21.
Objective:
To determine the value of measuring fetal ear length at 11-14 weeks of gestation in screening for chromosomal defects.
Methods:
The fetal ear length was measured in 450 fetuses immediately before chorionic villus sampling for karyotyping at 11-14 weeks of gestation.
Results:
The median gestational age was 12 (range, 11-14) weeks. The fetal ear was successfully examined in all cases. The fetal karyotype was normal in 409 cases and abnormal in 41, including 32 cases of trisomy 21. In the chromosomally normal group the fetal ear length increased significantly with crown-rump length from a mean of 3.7 mm at 45 mm to 6.9 mm at 84 mm. In the trisomy 21 fetuses the median ear length was significantly below the normal mean for crown-rump length by 0.45 mm (P = 0.013) but it was below the 5(th) centile of the normal range in only two (6.3%) of the cases. There was no significant association between the delta score of ear length and delta nuchal translucency in either the chromosomally normal (r = - 0.015, P = 0.753) or the trisomy 21 fetuses (r = - 0.014, P = 0.94).
Conclusions:
At 11-14 weeks of gestation the ear length in trisomy 21 fetuses is significantly reduced but the degree of deviation from normal is too small for this measurement to be useful in screening for trisomy 21.
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