2 A contracted midpelvis is a common cause for the occipito-posterior position or transverse arrest of the fetal head transverse arrest. In most cases these conditions lead to dystocia.1 Before full dilation in prolonged deliveries, a part of fetal head skin located on drug discovery cervix becomes swollen. The incidence

of swelling when the fetal head is located in the lower part of the canal is higher because the outlet provides a source of resistance to the fetal head which most likely occurs in the posterior occipital position and with cephalopelvic Inhibitors,research,lifescience,medical disproportion.1,21 According to the results of the current study, women who have experienced 6.8 times more dystocia had fetuses whose heads were swollen. In the present study women with transverse diagonal of the Michaelis sacral that was ≤9.6 cm experienced 6.1 times more dystocia. The Michaelis sacral is a rhombic space in the sacral bone. The upper angle is located between L5-S1 and the lower angle is consistent with the tip of the coccyx, the lateral Inhibitors,research,lifescience,medical angles are at the level of the superior Inhibitors,research,lifescience,medical posterior spins.22

Initially, Michael proposed the importance of this space for evaluation of pelvic capacity in 1851.8,23 The transverse diameter of this rhombus could be observed between cavities of superior posterior spines on the skin.23 According to a number of studies, an abnormal shape and size of the Michaelis sacral rhomboid area indicates an abnormal shape and size of the mother’s pelvis. The results of the present study have supported these findings. We observed that women with height to fundal height ratings of ≤4.7 experienced 2.6 times more dystocia. Logistic regression

analyses showed that maternal height and neonatal birth Inhibitors,research,lifescience,medical weight were not significant risk factors for dystocia Inhibitors,research,lifescience,medical by themselves. It could be concluded that a normal delivery could be possible despite the shortness of height or macrosomia. If height was in proportion to fetal size, the mother could experience normal delivery; a disproportionate fetal size to the mother’s height was more important in dystocia. Barnhard et al. observed a significantly lower mean height to fundal height ratio in the dystocia group compared to the normal delivery group (P=0.002),14 which was consistent with the result of the others present study. In the present study despite a lower mean for mother’s head circumference and higher rate of head circumference to height in the dystocia group according to logistic regression, these findings were not effective on dystocia. The higher ratio of head circumference to height in the dystocia group could be related to the shorter stature of women in this group. The only study in this field was conducted by Connolly et al. who noted opposite findings. These researchers reported higher mean head circumference in the dystocia group. They concluded that larger head circumference was a risk factor for dystocia.