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.