Spontaneous and iatrogenic preterm birth rates among unselected women in three consecutive pregnancies

We studied a population with three subsequent singleton deliveries within 10 year. The incidence of PTB decreased with 50% from the 1st to the 2nd pregnancy, to then stay relative stable in the 3rd pregnancy. Compared to PTB in the 1st pregnancy, PTB in the 2nd pregnancy is more predictive for the occurrence of PTB in the 3rd pregnancy.