Fig. 1. Schematic representation of the categories of preterm birth.

Spontaneous PTB and medically indicated PTB are two subtypes of preterm birth (PTB). Spontaneous PTB can be further subdivided into idiopathic PTB and preterm premature rupture of membrane (PPROM). In idiopathic PTB, uterine contractions and cervical dilation is followed by rupture of the fetal membrane before the expulsion of the baby out of the womb while in PPROM, the fetal membranes get ruptured before the initiation of uterine contractions before 37 weeks of gestational age. Medically indicated PTB can be further classified into pre-eclampsia, obstetrical complications, placental abruption, fetal distress, and intrauterine growth restriction.