I read with interest the article by Levine et al. The rate of spontaneous preterm birth (sPTB) in subsequent pregnancy, which was defined as spontaneous preterm labor or preterm premature rupture of membranes, was evaluated in women who had previously undergone induction of labor vs those who were in spontaneous labor at term ≥37 weeks’ gestation (index pregnancy). The authors excluded women with a history of preterm births (PTBs).
The authors observed that the induction of labor in term pregnancy (index pregnancy) was not a risk factor for subsequent sPTB, which is reassuring for clinicians. However, I have reservations about the authors’ other observation that women who experienced spontaneous early term (37 +0 to 38 +6 weeks’ gestation) birth in the index pregnancy had a 24% risk of sPTB in subsequent pregnancy. However, no explanation was offered for this association.
Chorioamnionitis (histologic and bacterial) is associated with late preterm and term births. The proportion of pregnancies that are complicated with chorioamnionitis decreases with advancing gestational age. Also, the proportion of neonatal adverse outcomes caused by bacterial sepsis decreases with advancing gestational age (37 +0 to 38 +6 and >39 weeks’ gestation). Chorioamnionitis as a contributory factor that leads to spontaneous early term births (37 +0 to 38 +6 weeks’ gestation) in index pregnancies and as a contributory factor in subsequent pregnancies that leads to spontaneous PTBs (preterm premature rupture of membranes and spontaneous preterm labor) was not evaluated by the authors.
With accurate dating of pregnancy at <20 weeks’ gestation, it is uncommon for women with no history of PTB to have late PTB in subsequent pregnancies solely because of spontaneous early term birth in their index pregnancy (ie, no underlying trigger).