The Effect of Histological Chorioamnionitis on the Short-Term Outcome of Preterm Infants Weighing ≤1,500 Grams: A Single-Center Study

Presenter: M. Rinaldi (e-mail: [e-mail])

Introduction: Chorioamnionitis or intra-amniotic infection is an acute inflammation of the membranes and chorion of the placenta, typically due to ascending polymicrobial bacterial infection in the setting of membrane rupture. It complicates as many as 40 to 70% of preterm births with premature membrane rupture or spontaneous labor and 1 to 13% of term births. The most common microorganisms that cause this pathology are: U. Urealyticum; M. Hominis; G. Vaginalis; E. Coli. Clinical, microbiological, or histological criteria can be used to diagnose chorioamnionitis. Histopathological examination of the placenta is the gold standard for evaluating antenatal inflammatory processes that might influence fetal development. Chorioamnionitis is often associated with significant maternal, perinatal and long term adverse outcomes. Adverse maternal outcomes include an increased risk of cesarean delivery, postpartum infection and sepsis, while adverse infant outcomes include stillbirth, premature birth, neonatal sepsis, brain injury and chronic lung disease. The purpose of this study was to determine whether or not histological chorioamnionitis is associated with adverse outcome in very low birth weight neonates (VLBW).

Materials and Methods: This was a retrospective study. The placental histopathologic findings and the charts of the VLBW patients who were admitted to neonatal intensive care unit of Azienda Ospedaliera Ospedali Riuniti di Foggia from January 2012 to December 2014 were reviewed. Histologic examination of placenta and extraplacental membranes were performed, and neonates’ clinical data were extracted from Vermont-Oxford Network. Analyses included χ² test, Student t-test, Fisher exact test, standard deviation and mean. Parametric and nonparametric statistics were used for data analysis.

Results: Among the 92 placentas examined, the frequency of acute histologic chorioamnionitis was 23% (21/92). Histological chorioamnionitis was associated with a greater frequency of nulliparity (80%), vaginal delivery (76%), lower gestational age (25 ± 1.95), lower birth weight (800 ± 201.47), Apgar score <7 at first (95%) and fifth minute (71%), retinopathy of prematurity (38%; OR: 3.2; 95% CI: [1.02; 8.78]) and necrotizing enterocolitis (5%; OR: 1.72; 95% CI: [0.14;19.93]). The mortality rate of newborns with maternal chorioamnionitis was of 33%. However, no significant difference was observed in the incidence of neonatal distress respiratory syndrome (100%), bronchopulmonary dysplasia (5%; OR: 1.13; 95% CI: [0.11; 11.38]), patent ductus arteriosus (9%; OR: 0.42; 95% CI: [0.08; 1.9]), periventricular leukomalacia and intraventricular hemorrhage (28%; OR: 2.5; 95% CI: [0.7; 5.84]) (see Table 1).

Conclusion: This study proves that premature neonates born from pregnancies complicated by histological chorioamnionitis have a lower birth weight, gestational age and Apgar score at first and fifth minutes than that without chorioamnionitis. Moreover, histologic chorioamnionitis is a risk factor for ROP and NEC, but not for other causes of major morbidity.

Keywords: chorioamnionitis, preterm, retinopathy of prematurity, necrotizing enterocolitis

Table 1 Demographics and main results

Characteristics	HCA (−)	HCA (+)	OR [95% CI]	p-value
Gestational age	29.42 ± 3.3	25.28 ± 1.95		<0.05
Birth weight	1101.5 ± 302	800 ± 201.47		<0.05
Maternal age	32 ± 5,8	32 ± 6,8
1-minute Apgar score < 7	42 (59)	20 (95)	13.8 [108.2; 1.76]	<0.001
A5-minute Apgar score < 7	22 (31)	15 (71)	5.56 [16.2; 1.9]	<0.01
Cesarean delivery	63 (89)	5 (24)	0.089 [0.27; 0.028]	<0.0001
IVH	14 (20)	6 (28)	2.5 [5.84; 0.7]	>0.05
PVL	0	0
ROP	12 (17)	8 (38)	3.2 [8.78; 1.02]	<0.05
NEC	2 (3)	1 (5)	1.72 [19.93; 0.14]	<0.05
PDA	14 (20)	2 (9)	0.42 [1.9; 0.08]	>0.05
LOS	2 (3)	0
EOS	3 (4)	2 (9)	2.38 [39; 0.14]	>0.05
RDS	64 (90)	21 (100)		>0.05
BPD	3 (4)	1 (5)	1.13 [11.38; 0.11]	>0.05