Background Neonatal mortality and morbidity in extremely preterm infants (< 28 weeks of gestation) have been extensively studied, but the risk added by intrauterine growth restriction remains controversial.
Aim To assess whether intrauterine growth restricted (small for gestational age, SGA) extremely preterm infants show a further increase in neonatal mortality and morbidity.
Methods The study included 9,888 singleton extremely preterm infants whose live birth was recorded at the Neonatal Research Network in Japan during 2003–2010. SGA was defined as birth weight at least 2SD below the mean for gestational age. The Risk of mortality and morbidity in the SGA group was evaluated by comparing outcomes for SGA against a non-SGA reference group.
Results Of the study subjects, 1,215 (12.3%) were SGA. Controlling for gestational age, sex, parity and multiple gestation, SGA infants showed a higher mortality rate during NICU stay compared with reference group infants (odds ratio [OR]: 4.23, p<0.0001). Severe neonatal asphyxia (OR: 1.89, p<0.0001), RDS (OR: 1.33, p<0.0001), chronic lung disease at 36 weeks’ postmenstrual age (OR: 2.23, p<0.0001), sepsis (OR: 1.95, p<0.0001), necrotizing enterocolitis (OR: 1.93, p<0.0001), focal intestinal perforation (OR: 1.46, p=0.011) and congenital anomalies (OR: 2.66, p<0.0001) were significantly associated with SGA status.
Conclusion Extremely preterm SGA infants are associated with increased the risk of neonatal mortality and major morbidity. These results are important for obstetric counseling and decision making and treatment of extremely preterm infants.