BACKGROUND
Preterm birth is defined as delivery prior to 37 weeks’ gestation. Although infants born toward the end of this period were traditionally assumed to be ‘low risk,’ research has unequivocally demonstrated increased rates of adverse neonatal outcomes associated with LP births (34+0–36+6 weeks). Compared with term infants, LP infants are more frequently admitted to the neonatal intensive care unit (NICU), and have longer hospital stay, due respiratory morbidities, temperature instability, hypoglycaemia, and hyperbilirubinaemia. Such population is also at higher mortality risk and it is more susceptible to sepsis, necrotizing enterocolitis, and neurological morbidities [1, 2, 3].
The LP rate in Western countries represents 3.3-5.7% of all births, accounting for about two thirds of the entire preterm population [4]. Despite the LP period is restricted to just 21 days of intrauterine development, perinatal well-being may vary [5]. The primary determinant of neonatal outcomes is gestational age at delivery; however, race, fetal gender, and administration of antenatal corticosteroids are also important factors affecting both survival and intact survival [6]. Recent research suggests that also indication for delivery significantly impacts neonatal outcomes [7, 8]: studies on both preterm [7] as well as LP births [9] showed worse outcomes among medically indicated as opposed to spontaneous preterm deliveries. Furthermore, among births prior to 34 weeks, intrauterine growth restriction (IUGR) was found to have increased neonatal risks [10, 11] , while fetal or obstetric indications for delivery lead to higher neonatal morbidity when compared to maternal indications [12]. However, the role of specific maternal (such as hypertensive disorders, diabetes mellitus) or fetal risk factors (such as IUGR, amniotic fluid abnormalities) on neonatal outcomes is still a matter of debate, when they are not directly responsible for LP deliveries. Moreover, the outcomes of late LP premature rupture of membranes have not been compared to other delivery indications.
With this study we sought to expand our understanding of how neonatal risks in the LP period may vary according to the timing and the indication for delivery, in order to personalize prenatal counseling, as well as obstetric care for individual mothers and their newborns. Therefore, we investigated a large prospective cohort of LP neonates to determine:
1) if neonatal outcomes differ according to the specific gestational age at delivery (34 vs 35 vs 36 weeks’ births), as gestational age does not affect management of pregnancies when delivery is anticipated between 34+0 and 36+6 weeks
2) if neonatal morbidity varies based on the circumstances at parturition (spontaneous preterm labor (PTL), preterm premature rupture of membranes (pPROM), or indicated delivery)
3) if complications at birth are affected by specific maternal, fetal and obstetric conditions, even if they may not represent the indication for delivery.