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Physiological immaturity plays primary role in late preterm infant morbidities
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Younger gestational age in late preterm infants was more likely to contribute to morbidities resulting in hospital stay compared with causes of preterm delivery, according to research presented at the Pediatric Academic Societies 2018 Meeting
“Our study investigated if common neonatal complications in late preterm infants are related to the reasons for preterm birth,” Melissa Lorenzo, MD, of Queen’s University, Kingston, Ontario, told Infectious Diseases in Children. “We examined the three most common causes of preterm birth. including medically indicated reasons, preterm premature rupture of membranes and threated preterm labor.”
“Our results demonstrated that younger infants were significantly more likely to suffer complications such as jaundice, respiratory distress and requirement for respiratory support (babies born at 34 weeks [are] more likely to suffer complications [than] those at 35, or 36 weeks),” Lorenzo continued. “Surprisingly, the reasons for preterm delivery did not impact the risk of developing neonatal complications.”
Lorenzo and colleagues noted that the preterm population consists of 70% late preterm infants (LPTs), with higher neonatal morbidities compared with term infants.
“Although this increased risk is attributed to physiological immaturity, recent studies indicate that immaturity itself may not be the sole cause of morbidity as all premature infants experience this risk but suffer different outcomes,” the researchers wrote. “Some studies demonstrate the risk of morbidities is determined by the causes of preterm delivery with immaturity acting as a modulator.”
The researchers conducted a retrospective cohort study of LPTs who were between 34 0/7 weeks’ and 36 6/7 weeks’ gestation and born from April 2014 to February 2016 at a single tertiary care center. Threatened preterm labor (TPTL), preterm premature rupture of membranes (PPROM) and medically indicated deliveries, including maternal and fetal pathologies were categorized as implications of birth.
Unadjusted and adjusted age risk ratios were calculated by multiple regression analysis, with PPROM as a reference category. This estimated hypoglycemia, hyperbilirubinemia, use of continuous positive air pressure and apnea of prematurity in LPT.
The researchers studied 279 infants. They found that 38.4% of deliveries resulted from PPROM, 22.8% from TPTL and 39.1% from obstetric and fetal indications.
The most common reasons for medically indicated preterm deliveries were pre-eclampsia and intrauterine growth.
Most infants born through medically indicated deliveries (67.6%) were classified small for gestational age (P = .001), delivered via cesarean section (62.9%; P = .001) and received antenatal steroids (53.3%; P = .02). Almost half were boys (49.5%), and the length of hospital stay averaged 9.39 ± 7.7 days.
Increased risk of morbidities showed significance in relation to lowered gestational age. Hypoglycemia was the exception, with the highest incidence at 36 weeks (66.7%) compared with much smaller percentage of incidence at 35 weeks (28.5%) and 34 weeks.
“However, none of the morbidities were significantly associated with any indication of birth with or without adjustment of age,” the researchers wrote.
“Our study demonstrated that immaturity related to gestational age, rather than the reasons for preterm delivery, is the primary contributor in the development of late preterm complications.,” Lorenzo said. – by Bruce Thiel
References:
Lorenzo M, et al. Morbidity risk among late preterm infants: Immaturity vs. indication of delivery. Presented at: The Pediatric Academic Societies 2018 Meeting; May 5-8, 2018; Toronto.
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Sheri Nemerofsky, MD, FAAP
Lorenzo and colleagues conducted a retrospective assessment of whether the indication for late preterm (34 0/7-36 6/7 weeks) delivery had an influence on neonatal morbidity. The three indications included TPTL, PPROM and medically indicated delivery for either maternal or fetal pathologies. Unlike other studies, they determined that there was no difference among these groups on infant morbidity. As expected, the incidence of hyperbilirubinemia, use of CPAP and apnea had an inverse relationship with gestational age. This is a common occurrence in our hospital system and among preterm infants. One unexpected finding in their study found the more mature infants had a higher risk of hypoglycemia. We have not found this to be the case.
The incidence of LPTs has remained significant throughout the last decade. Research on this group of infants continues to be important because we need to address the needs of this population both inside the hospital and after discharge. Institutional guidelines vary for neonatal care unit (NICU) admissions by gestational age. In the population presented here, all babies born before 36 weeks’ gestation were directly admitted to the NICU. It is unclear as to how many patients born at 36 weeks were asymptomatic and remained with their mother. At our institution, most newborns aged 35 and 36 weeks can stay with their mothers in the newborn nursery and the only babies born before 35 weeks are directly admitted to the NICU.
Lorenzo and colleagues determined that physiological immaturity in LPTs and not the indication for delivery causes neonatal morbidity. In the future, they could consider examining the differences between those who were admitted to the NICU and those who were not. Research on late preterm infants must continue in order to improve outcomes for this population.
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