A pregnancy that reaches or exceeds 42 weeks of gestation is clinically referred to as a term pregnancy, and its incidence ranges from 5% to 12% of all pregnancies. The rate of fetal perinatal disease and mortality is increased in term pregnancies and worsens with longer gestation, with perinatal mortality three times the normal rate at 43 weeks of gestation and five times the normal rate at 44 weeks. The risk of fetal distress, reduced amniotic fluid volume, delivery difficulties and injury to the fetus and mother are all associated with the increased risk of a term pregnancy in primiparous women compared to menstrual women. The causes of preterm pregnancy are not very clear, as there are many possible factors that can trigger labor, including progesterone blockade, oxytocin stimulation and fetal adrenocorticotropic hormone secretion, and any factor that causes an imbalance of these hormones can lead to a preterm pregnancy.