Preterm labor occurs between the 20th and 37th week of pregnancy. This labor includes both uterine contractions and cervical changes.

A full-term pregnancy lasts 38-42 weeks but preterm labor can lead to early delivery. Infants born before 37 weeks are considered premature.

In most cases, the cause is of preterm labor is unknown.

Some preterm labor is associated with preterm premature rupture of membranes (PPROM). PPROM is the rupture of both the amniotic sac and chorion membranes. It generally occurs at least one hour before labor begins.

Amniotic Sac
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