Vomeronasal organ growth and development in normal and cleft lip and palate human fetuses

As part of an ongoing investigation of normal and cleft lip and palate (CLP) fetal midfacial development, the vomeronasal organ (VNO) was examined in 35 human fetuses (26 normal and 9 CLP) ranging in age from 8 to 30 weeks postmenstrual age. All specimens were examined histologically, and a computer reconstruction technique was used to quantify lengths and volumes of right and left VNOs and anterior paraseptal cartilages (PCs). Growth curves were generated for these data and were compared between normal and cleft samples. VNOs and PCs were present in all normal fetuses, whereas VNOs were found in only 5 of 9 CLP specimens and PCs were found in 8 CLP specimens. The side of the palatal cleft in specimens with unilateral CLP was associated with PC dysmorphologies but appeared to have no influence on VNO presence or absence. Septal dysmorphologies were observed in most CLP specimens with absent or abnormal VNOs. VNO length increased in a linear fashion across ages, and VNO volume was seen to change in a logarithmic fashion. Individual CLP specimens did not differ significantly from the mean of the normal sample for VNO length or volume. PC length was seen to change in a sigmoidal fashion, and PC volume changes were best described by a logarithmic curve. In contrast to findings on the VNO, CLP specimens exhibited significantly different growth rates (line slopes) for PC length and volume compared to the normal sample. Results on the normal sample suggested that the human fetal VNO exhibits volumetric increases between the 16th and 30th weeks of development, but this increase begins later and proceeds more slowly than that of the PCs. Examination of the CLP sample suggested that the VNOs were of "normal" size for age, but may be vulnerable to septal dysmorphologies that result in altered location or disruption.