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To define normal growth of the fetal maxillary dental arch using magnetic resonance imaging.Four hundred twenty-four consecutive fetuses (18 to 37 weeks) with a morphologically normal anatomy or only minor malformations, not affecting bone growth and face anatomy were included. On axial T2-weighted images the dental arch length and width were measured. The measurements were correlated with gestational age and the biparietal diameter (BPD) of the fetal head using correlation and regression analysis.A linear growth relationship was observed between the dental arch length and gestational age (r = 0.86; p = <0.0001; y = −1.85 + 0.75 × gestational age) and the dental arch width and gestational age (r = 0.92; p = <0.0001; y = −2.19 + 1.05 × gestational age). A significant correlation was found between the dental arch length and the BPD (r = 0.903; p = <0.0001) and the dental arch width and the BPD (r = 0.927; p = <0.0001). The interobserver variability showed good agreement for the dental arch length (intraclass coefficient 0.981; r = 0.963) and width (intraclass coefficient 0.987; r = 0.974), respectively.We present a nomogram for the in utero assessment of the fetal dental arch. These data may help in the early detection of abnormal dental arch development. © 2012 John Wiley & Sons, Ltd.