Evidence to support that spontaneous preterm labor is adaptive in nature: neonatal RDS is more common in “indicated” than in “spontaneous” preterm birth

Abstract

Objectives: The onset of preterm labor has been proposed to have survival value and to be adaptive in nature. This hypothesis would predict that induced preterm birth may be associated with higher rates of complications than spontaneous preterm birth. The purpose of this study was to determine if there is a difference in the frequency of neonatal respiratory distress syndrome (RDS), the most common neonatal complication, according to the etiology of preterm birth (e.g., preterm labor wPTLx, preterm PROM, or pregnancies which ended because of maternal-fetal indications). Study design:The relationship between the occurrence of RDS and the obstetrical circumstances leading to preterm birth was examined in 257 consecutive singleton preterm births (gestational age: 24-32 weeks). Cases with major congenital anomalies were excluded. The study population was divided into two groups according to the cause of preterm birth: 1) preterm birth due to PTL with intact membranes or preterm PROM (spontaneous preterm birth group); and 2) preterm birth due to maternal or fetal indications (indicated preterm birth group). Results: 1) RDS was diagnosed in 47% of cases; 2) RDS was more common in patients with indicated preterm birth than in those with spontaneous preterm birth group (58.1% vs. 38.4%, Ps0.002); 3) Patients with indicated preterm birth had a significantly higher mean gestational age at birth, but lower mean birth weight, lower rate of histological chorioamnionitis and higher rates of cesarean delivery, 5 min Apgar score of -7, and umbilical arterial blood pH of -7.15 than those with spontaneous preterm birth (P-0.05 for each); 4) Antenatal corticosteroids were used in 73.4% of cases with indicated preterm birth and in 76.9% of those with spontaneous preterm birth; 5) Multivariate analysis demonstrated that indicated preterm birth was associated with an increased risk of RDS after adjusting for confounding variables (ORs2.29, 95% CI 1.22-4.29). Conclusions: 1) The rate of RDS is greater following ''indicated'' rather than spontaneous preterm birth; 2) This observation supports the view that spontaneous preterm labor is adaptive in nature.

Immediate delivery compared with expectant management after preterm pre-labour rupture of the membranes close to term (PPROMT trial): a randomised controlled trial

“…These risks are thought to be associated with both gestational age and biological factors associated with the preterm birth, including PPROM 25 , however, immediate delivery does not appear to improve outcomes in preterm neonates and may exacerbate the risks of prematurity because of birth in the absence of labor and earlier gestational age. Although expectant management in a potentially hostile intrauterine environment should be avoided, in a mother who remains well, with no evidence of clinical chorioamnionitis, expectant management provides an opportunity for spontaneous labor to develop and for adaptive changes to occur in the neonate resulting in decreased risk of neonatal respiratory illness 26 . For some neonates, expectant management may also result in delivery at a substantially older gestational age.…”

Mild to Moderate, but Not Minimal or Severe, Acute Histologic Chorioamnionitis or Intra-Amniotic Inflammation Is Associated with a Decrease in Respiratory Distress Syndrome of Preterm Newborns without Fetal Growth Restriction

“…However, the effect of acute histologic chorioamnionitis (acute-HCA) on the development of respiratory distress syndrome (RDS) is still controversial [2]. Acute-HCA is known to be associated with a decreased risk of RDS [3,4], but some human studies do not show this relationship [5,6]. Moreover, no study about the relationship between intra-amniotic inflammation (IAI) and the development of RDS has been reported in human pregnancy, although intra-amniotic injection of inflammatory cytokines and endotoxin in animal model shows an increase in markers that would be considered to be associated with decreased RDS (i.e.…”

543: Presenting twins are exposed to higher levels of inflammatory mediators than non-presenting twins as early as the mid-trimester of pregnancy

“…In animal studies, intra-amniotic administration of endotoxin or inflammatory cytokine accelerated lung maturation by increasing the production of airway surfactant and improving lung gas exchange, which has been suggested as the mechanism by which antenatal corticosteroids act to promote functional maturation of the fetal lung [18][19][20][21][22][23][24]. Recent studies suggest that chorioamnionitis is associated with the decreased risk of neonatal respiratory distress syndrome, thereby supporting the theory that pulmonary maturation is accelerated in the presence of antenatal inflammation [14,[25][26][27][28][29][30]. Increased endogenous cortisol levels have been suggested as the possible mechanism for this relationship, since cortisol can increase surfactant synthesis in the presence of inflammation as well as increase pulmonary fluid clearance and subsequent gas exchange in the presence of MMPs and neutrophils [25].…”

“…The precise reason for this difference is not well understood, although it has been shown that the presence of inflammation reduces the risk of respiratory morbidity in singleton pregnancies [14]. We postulate that first twins are exposed to higher levels of inflammatory mediators than second twins, and that this may be true throughout pregnancy and not only at term when the cervix is effaced and dilated thereby allowing for ascending infection and inflammation.…”