INTRODUCTION
Labor is a continuous, multifaceted process divided into three stages.1 The first stage refers to the time from the beginning of labor until the cervix is fully dilated.123 The second stage describes the time from full cervical dilation to delivery of the baby.1456The time from the expulsion of the baby to the removal of the placenta refers to the third stage.17
The first stage consists of two parts, latent and active. According to current studies, the latent phase defines as 0 to 6 cm, and however, the active phase means the duration between 6 cm and full cervical dilation.138910
Based on formal Friedman’s study, the latent phase duration in nulliparas must be shorter than 20 hours and in multiparas, faster than 14 hours after the onset of the latent phase.811 The active phase (time from 6 to 10 cm) is more rapid than the latent phase in both induced and spontaneous labors.1213 Active phase protraction means cervical dilatation in women with ≥6 cm and dilatation duration of less than about 1 to 2 cm/hour.10 Active phase arrest defines that in a pregnant woman with a cervical dilatation of ≥6 cm and ruptured membranes; no cervical changes for ≥4 hours despite adequate contractions or ≥6 hours even if contractions are inadequate.381014
The optimal duration for the second stage of labor is still controversial. Based on current data, it suggested for a nulliparous patient 3 hours and 2 hours for a multiparous woman. If regional anesthesia is performed, we can wait for 1 hour more.181415 Longer times may be defined as second stage arrest.
The protraction or arrest in the first or second stage of labor is a significant risk factor for the primary cesarean. Maternal obesity, macrosomia, cephalopelvic disproportion, neuraxial anesthesia, occiput posterior position, nulliparity, uterine abnormality, short stature (less than 150 cm), maternal age, post-term pregnancy, and hypocontractile uterine activity states are associated with prolongation and arrest of birth.1617
In the first stage of labor, especially in the active phase, oxytocin augmentation and amniotomy may be an option for labor progression.18 But women with labor arrest in the first stage should be managed by cesarean delivery.15When the second stage arrest diagnosed, the obstetrician should consider the options including observation, operative vaginal delivery, and cesarean delivery if the maternal and fetal conditions permit.16
Prolonged delivery may cause some maternal and fetal complications. In the literature, the studies show that a longer duration of the active phase and second stage of labor may be associated with risk of operative vaginal delivery, cesarean delivery, perineal lacerations, postpartum hemorrhage, chorioamnionitis, shoulder dystocia, increased risks for neonatal intensive care unit requirement, Apgar score decrease,  hypoxic-ischemic encephalopathy and fetal mortality.151619202122232425
Fetal soft tissue composite is in relation with gestational diabetes, macrosomia, the risk for cesarean delivery and neonatal adiposity.2627282930
Shoulder dystocia is one of the serious obstetrical complications as it can cause permanent plexus brachialis injury. It occurs in 0.2 percent of births. Although there are several known risk factors, the clinicians often can not predict the shoulder dystocia. Clinicians should consider the risk factors for shoulder dystocia and should be prepared to address this complication in all deliveries.31 Shoulder dystocia is a subjective clinical diagnosis, but there are some studies as more objective definition criteria in the literature.3233
We have mentioned above the risk factors in prolonging labor. In this study, we will examine the relationship between fetal adipose tissue thickness without these risk factors but associated with them, prolongation of delivery and complications caused by this. In this context, it may be the first study in the literature regarding the relationship between fetal adipose tissue thickness, prolonged delivery, shoulder dystocia, and cesarean delivery.