Received: February 05, 2010;
Initial review: March 03, 2010;
Accepted: June 28, 2010.
Published online: 2010 November 30.

Understanding morbidity risk among late-preterm infants is not only important for helping newborn care providers to anticipate and to manage potential morbidity during the birth hospitalization and earlier follow-up after hospital discharge, but also may possibly assist in guiding non-emergency obstetric intervention decisions. The present study is an attempt to obtain actual data on incidence, pattern of early neonatal morbidities, and to compare it with term infants.

This hospital-based prospective cohort study was conducted at the Fernandez Hospital, Hyderabad, an urban private tertiary care women and newborn hospital. The study was approved by the hospital ethics committee. All live inborn late preterm infants (34 0/7 to 36 6/7 weeks) and term infants (37 0/7 to 41 6/7 weeks) [5] born between February 2009 to September 2009 were eligible for enrollment in the study. Informed parental consent was obtained prior to enrolment in the study. Infants with major congenital anomalies and those with clinically identified chromosomal syndromes were excluded. Gestational age was assessed by maternal last menstrual period and by first trimester ultrasound scan.

There were 3300 live births in hospital during study period. Of these, 371 (11.24%) were late preterm and 2725 (82.58%) were term births. Three hundred sixty three (98.65%) of late preterm infants and 2707 (99.33%) of term infants were included in the study. Twenty two infants were excluded due to congenital anomalies and in 4 cases parental consent was refused. All included infants were followed for 7 days of life for outcomes. On comparing the two groups, there was significant difference in mean gestation, mean birthweight, weight for gestation, mean Apgar score, mode of delivery, and multiple pregnancy status (Table I).

TABLE I



Baseline Variables of The Study Population 

257 (70.8%) of late preterm and 788 (29.1%) of term infants had atleast one of the neonatal morbidities requiring inpatient hospital observation, admission or readmission during the first 7 days of life. On comparing the neonatal morbidity after adjusting for mode of delivery, intrauterine growth, and multiple pregnancy status; late preterm infants were at significantly higher risk for overall morbidity due to any cause, respiratory morbidity, any ventilation (non invasive or invasive), jaundice, hypoglycemia, probable sepsis, and confirmed sepsis (Table II). Thirty six (9.9%) late preterm infants and 199 (7.4%) term infants required readmission in the first 7 days of life (Table III). As 40 weeks is considered an ideal gestation age for delivery, neonatal morbidities at each of the lower gestations was compared with morbidities of neonates born at 40 weeks. The incidence of morbidities increased from 23% at 40 weeks to 30%, 39.7%, 67.5%, 89% and 87.9% at 38, 37, 36, 35 and 34 weeks, respectively(Fig. 1).

TABLE II



Comparison of Morbidity in Late Preterm and Term Infants

Fig. 1 Neonatal morbidity: Individual gestation vs reference term (40 weeks).

In the present study, 70.8% of late preterm and 29.1% of term infants had at least one neonatal morbidity requiring inpatient hospital observation, admission or readmission during the first 7 days of life. Neonatal jaundice requiring phototherapy (55.1%) followed by respiratory morbidity (10.5%) and hypoglycemia (8.8%) were the frequently identified morbidities in late preterm infants while neonatal jaundice (24.8%) was the most frequently identified morbidity in term infants. Cesarean delivery, IUGR and multiple pregnancy status significantly contribute to neonatal morbidities. Compared with term infants, these variables are more common in late preterm infants. In order to neutralize the influence of these variables on the outcomes evaluated, adjusted odds ratios were calculated and were significantly higher in late preterm group. Compared with term infants, late preterm infants were at 5.5 times higher risk for overall morbidity due to any cause, 7.5 times higher risk for respiratory morbidity, 4.2 times higher risk for ventilation (non invasive or invasive), 3.4 times higher risk for jaundice, and 4.5 times and 3.2 times higher risk for hypoglycemia and probable sepsis, respectively.

Similar to our findings, in a retrospective study by Wang, et al.[1], 77.8% near term infants compared with 45.3% of term infants had at least one clinical problem and nearly all clinical outcomes differed significantly between near-term and full-term neonate viz. temperature instability, hypoglycemia, respiratory distress, and jaundice. They found that during the initial birth hospitalization, late preterm infants were 4 times more likely than term infants to have at least one medical condition diagnosed and 3.5 times more likely to have two or more conditions diagnosed [1]. Melamed, et al. [6] also found that compared with full-term infants, spontaneous late preterm delivery was independently associated with an increased risk of neonatal morbidity, including respiratory distress syndrome, sepsis, intraventricular hemorrhage, hypoglycemia, and jaundice requiring phototherapy. Another study Tomashek, et al. [7] found that late preterm infants were 1.5 times more likely to require hospital-related care and 1.8 times more likely to be readmitted than term infants. In another study, newborn morbidity was 7 times more likely in late preterm compared with term infants (22% vs 3%) [8]. The higher risk for neonatal morbidity in our study may be attributed to the inclusion of neonates of 34 weeks gestation in our data, difference in definition of morbidities, and a more precise follow-up due to it being a hospital based prospective study than previous studies, which are either retrospective or were based on population data.

The incidence of morbidity increased from 24% at 40 weeks to 90% at 34-35 weeks showing an inverse relationship with gestational age. There was a 10% increase from 38 weeks to 37 weeks, 20% increase from 37 weeks to 36 weeks and 30% from 36 weeks to 35 weeks. With 40 weeks as reference standard, all gestations except 39 weeks were at significantly higher risk for morbidity. Bradley, et al. [9] concluded previously that clinically significant respiratory morbidities are least common at 39-40 weeks. Roberta De Luca, et al. [10] similarly found that mortality and morbidities had a strong GA-related trend with the lowest incidences consistently found between 38 and 40 weeks of gestation. Shapiro-Mendoza, et al. [8] found that the newborn morbidity rate doubled in infants for each gestational week earlier than 38 weeks.

The present study is one of the first attempts to obtain actual data on late preterm births and associated neonatal morbidities from India. A major limitation of present study is inability to assess feeding difficulties and breastfeeding status. This was because of existing policy of the unit to give supplementary feeding to all at risk infants. As the present study was designed to asses early neonatal morbidities, it did not address morbidities after 7 days of life, and also whether outcomes studied had long-term implications. Among the neonatal units, often there is as a wide variation in antenatal use of steroids, intrapartum monitoring, feeding policy, asepsis protocols and management of jaundice/ respiratory distress and hence the results of this study may be more applicable to settings similar to ours and may not be generalizable.

The results show that late preterm infants have 5.5 times higher risk for overall morbidity due to any cause relative to term infants. All gestations except 39 weeks were at significantly higher risk for morbidity with 40 weeks as reference term.

Contributors: SM designed and supervised the study. AJ collected and analyzed the data. All the authors contributed in preparation and approved final manuscript.

Funding: None.

Competing interests: None stated.