The PLART study: incidence of preterm labor and adverse pregnancy outcomes after assisted reproductive techniques—a retrospective cohort study

Even though assisted reproductive techniques represent one of the greatest achievements in modern medicine, the risk of preterm birth related to these pregnancies is about twice as high. This must be highlighted and further investigated to optimize the management of both mothers and newborns. The purpose of this study was to compare adverse pregnancy outcomes after assisted reproductive techniques (ART) and spontaneous conceptions, focusing on the incidence of preterm births (PTB) and distinguishing between iatrogenic and spontaneous events. This retrospective cohort study analyzed single births of one Italian hospital. The incidence of PTBs in ART pregnancies, divided into iatrogenic procedures, spontaneous preterm labors and preterm premature ruptures of the membranes (pPROMs), was compared with the non-ART control group. The incidence of other adverse pregnancy outcomes and the types of delivery were also reported and compared. Of the 11,769 single births included, 2.39% were conceived by ART. The incidence of PTBs was 4.74% for spontaneous pregnancies and 12.8% for ART pregnancies (aOR 1.93; 95% CI 1.29–2.88). The percentage of iatrogenic procedures was 27.78% in the ART-PTBs’ group and 30.88% in the non-ART-PTBs’ controls. ART pregnancies showed an increased incidence of pPROMs (6.40% versus 2.41%), preterm labors (2.85% versus 0.93%), hypertensive disorders of the pregnancy (8.19% versus 2.32%), placenta previa (3.20% versus 0.59%), cesarean sections (28.47% versus 16.27%) and vacuum extractions (10.32% versus 5.19%). Singleton ART pregnancies have a higher risk of PTB which is mostly linked to a higher incidence of pPROMs and spontaneous preterm labor. The concurrency of a demonstrated higher risk of hypertensive gestational disorders and placenta previa suggests that placental development plays an important role in the pathogenesis of PTB.