RESULTS
Among the 1897 LP births, 302 (16.2%) occurred at 34 weeks’, 504 (27%)
at 35 weeks’ and 1061 (56.8%) at 36 weeks’ gestation. Spontaneous
preterm labor accounted for 686 (36.7%) deliveries, pPROM for 398
(21.3%), while 783 (42%) were indicated LP births.
Table 1 summarizes the maternal and obstetrics characteristics of the
study population presented by gestational age at delivery. Demographic
features, socioeconomic attributes, medical complications (hypertensive
and liver disorders, chorioamnionitis), prophylaxis with ASA or LMWH
were similar across different gestational age groups. Only 4 patients
developed pPROM < 34 weeks’ gestation. Diabetes mellitus was
more common among mothers who delivered at 34 weeks’ gestation (p
< 0.01), pPROM was more prevalent among pregnancies resulting
in 36 weeks deliveries (p = 0.03), while vaginal bleeding due to
abruption or abnormal placentation was less frequent among gestations
leading to 36 weeks as opposed to earlier births (p < 0.01).
Antenatal corticosteroids and progesterone prophylaxes progressively
decreased with gestational age (p < 0.01). The last (and for
605/634 the only course) of antenatal corticosteroids was administered
to 237 (37.4%) patients < 34 weeks’ gestation, while 397
(62.6%) received the treatment later. Induction of labor was more
common later in pregnancy, as opposed to CDs performed prior to labor
onset (p < 0.01); the vaginal delivery rate increased with
gestational age at delivery (p < 0.01).
Thirty-four women (4%) were diagnosed with pPROM prior to 34 weeks’
gestation, while 809 (96%) later. The median interval from rupture of
membranes to delivery was 4 days (95%CI 2 -5 days). Antibiotic
treatment was administered to 699 (83%) women with pPROM; although
details about the duration of treatment were available for only 634
women, the vast majority (i.e. 610, 96%) received a ≤ 7 day-course.
Fetal characteristics are displayed in table 1. Non reassuring fetal
status, prenatally diagnosed fetal anomalies, and amniotic fluid
abnormalities were similar among study groups, while IUGR was
significantly less common when delivery occurred closer to term (p
< 0.01). Circumstances at parturition (spontaneous PTL, pPROM
or indicated deliveries) did not differ according to timing of delivery
(Table 2). Instead, most neonatal outcomes were affected by gestational
age (Table 3). No cases of neonatal deaths were detected in our study
population. The prevalence of metabolic acidosis and respiratory support
dropped with gestational age at delivery (p < 0.01), while 5’
Apgar score and cardiopulmonary resuscitation remained unaffected (Table
3). Later deliveries were associated with higher birthweights, higher
proportions of SGA infants, as well as lower rates of jaundice,
difficulty feeding, hypoglycemia and sepsis (p < 0.01).
The composite neonatal outcome was detected among 27.1% (82/302) of the
34 weeks deliveries, 17.7% (89/504) of the 35 weeks deliveries, and 8%
(85/1061) of the 36 weeks births (p < 0.01). Similarly, the
composite outcomes respectively summarizing metabolic complications, and
respiratory support decreased when delivery occurred closer to term,
while the risk of metabolic acidosis and/or neonatal resuscitation was
unaffected by timing of delivery (Table 3).
Multivariate analysis showed that gestational age at delivery had the
most significant impact on the composite neonatal outcome, metabolic
complications, and the need for respiratory support. Table 4 summarizes
the multivariate logistic regression models investigating the role of
timing and circumstances at delivery. Neonatal morbidities decreased
with gestational age at delivery (p < 0.01), and were
associated with indicated births (p < 0.01); of note, outcomes
of pregnancies delivered due to pPROM were similar to spontaneous PTLs
(Table 4). Instead, timing of delivery did not affect neonatal
resuscitation, that appeared to be uniquely associated to deliveries
indicated by maternal, fetal or obstetric complications (p <
0.01). Table 5 illustrates the multivariate logistic regression models
assessing the impact of maternal medical conditions, fetal
characteristics, pregnancy complications, and gestational age at
delivery on neonatal morbidities. As gestational age increased, the
composite neonatal outcome, metabolic complications and the need for
respiratory support dropped (p < 0.01). Considering the same
outcome measures, pregestational diabetes was a significant risk factor
for neonatal morbidities (p =0.02, < 0.01, and <
0.01 respectively), while preeclampsia showed a protective effect (p
=0.03, < 0.01, and 0.04 respectively). Vaginal bleeding due to
abruption or abnormal placentation (p = 0.03), increasing maternal BMI
(p = 0.03, and 0.02 respectively), and polyhydramnios (p = 0.045, and
< 0.01 respectively) were significantly associated with both
the composite neonatal outcome and respiratory support, while pPROM (p
< 0.01) was solely associated with the composite neonatal
outcome. Non-reassuring fetal status was related to both metabolic
complications (p < 0.01), and respiratory support (p = 0.04);
instead, spontaneous PTL (p < 0.01) had a protective effect on
the risk of metabolic complications, as opposed to IUGR (p <
0.01). Gestational age at delivery did not affect the risk of metabolic
acidosis and/or neonatal resuscitation; the likelihood of such outcome
was associated with bleeding due to placental abruption or abnormal
placentation (p < 0.01), as well as with non-reassuring fetal
status (p < 0.01).