Perinatal characteristics and outcome of preterm singleton, twin and triplet infants in NSW and the ACT, Australia (1994–2005) P Garg, 1 M E Abdel-Latif, 1,2 S Bolisetty, 1 B Bajuk, 3 T Vincent, 3 K Lui 1,2 1 Department of Newborn Care, Royal Hospital for Women, NSW, Australia; 2 School of Women’s and Children’s Health, University of New South Wales, NSW, Australia; 3 Neonatal Intensive Care Units’ (NICUS) Data Collection, NSW Centre for Perinatal Health Services Research, NSW, Australia Correspondence to: Associate Professor K Lui, Department of Newborn Care, Royal Hospital for Women, Locked Bag 2000, Randwick, NSW 2031, Australia; k.lui@ unsw.edu.au Accepted 29 July 2009 Published Online First 9 August 2008 ABSTRACT Objective: To compare the perinatal characteristics, neonatal morbidity and mortality of preterm singletons, twins and triplets born at 22–31 weeks’ gestation and admitted to neonatal intensive care units (NICU) in New South Wales and Australian Capital Territory between 1994 and 2005. Methods: Perinatal characteristics and neonatal outcome data were obtained from the regional NICUS data collection to test for a priori hypothesis. The 10 068 very premature infants studied included 7304 (72.5%) single- tons, 2444 (24.2%) twins and 320 (3.2%) triplets. Results: Assisted conception was associated with a higher maternal age and increased twins and triplets admissions into NICU than spontaneous conceptions (twins OR 6.9, 95% CI 6.1 to 8.0; and triplets OR 35.6, 95% CI 27.6 to 45.8). Major neonatal morbidities were similar between the three groups of singletons, twins or triplets. While twins of 22–27 weeks’ gestation (adjusted OR 1.39, 95% CI 1.12to 1.72) had higher mortality compared with singletons, mortality only diverged below 24 weeks’ gestation. Mortality was predicted by decreasing gestational age, male gender and lack of antenatal steroids, whereas assisted conception was protective against mortality (adjusted OR 0.69, 95% CI 0.57 to 0.86). Conclusions: Assisted conception contributed to higher very premature NICU admissions of twins and triplets. Preterm twins at the very extreme of viability had higher mortality compared with singletons. The protective effect of assisted conception against mortality requires further research. From the mid-1970s, there has been an enormous increase in the number of twin and triplet pregnancies in the western world. 12 Up to one third of this increase is attributable to an increase in the maternal age and up to 50% of twin pregnancies and 75% of triplet pregnancies occur after infertility treatment. 23 Twin and higher order multiple pregnancies are associated with an increase in perinatal mortality and morbidity, compared with singleton pregnancies. This increase in perinatal mortality and morbidity is largely due to a higher incidence of delivering preterm. There are a few studies that reported the differences in outcomes between preterm infants of multiple gestation and preterm singletons, 4–7 but none of these studies has reported on the effects of assisted conception on the outcomes in these infants. The present study was aimed at all infants of less than 32 weeks’ gestation admitted to the tertiary neonatal intensive care units (NICU) in New South Wales (NSW) and the Australian Capital Territory (ACT) to test the hypothesis that twins and triplets have higher mortality and predischarge morbidities than singletons at this gestational age. METHODS AND SUBJECTS Data source The data for this study was extracted from the NICUS data collection, which is a population-based prospec- tively collected state-wide audit of infants admitted to all 10 NICU (eight perinatal centres and two children’s hospitals) in NSW and the ACT during the neonatal period for one of the following reasons: gestational age less than 32 weeks’ gestation, birth weight less than or equal to 1500 g, assisted ventila- tion (mechanical ventilation or continuous positive airways pressure) for 4 h or more commenced during the first 28 days of life and major surgery (opening of a body cavity first performed in the first 28 days of life). Neonatal, maternal and perinatal data were prospec- tively collected and collated within each NICU by a designated clinical nurse specialist. NICU group uses standard operational definitions across all the net- work (B Bajuk, T Vincent, and the NSW and ACT Neonatal Intensive Care Units’ (NICUS) Group, unpublished). These data were compiled into a central database located at the NSW Pregnancy and Newborn Services Network, where they underwent rigorous quality control procedures and the accuracy of the NICU data collection was validated. 8 For this study, only 22–31 weeks’ gestation infants admitted to one of the collaborating NICU during the period 1994–2005 were included. We excluded quadruplets (n = 12, 0.1%) from the outcome analysis as the number of these neonates was small. For retinopathy of prematurity and intraventricular haemorrhage the denominator was the number of babies who had an eye examination or a head ultrasound, respectively. What is already known on this topic c Preterm multiple births are increasing. c Assisted conception contributes to increased preterm multiple births. What this study adds c Preterm infants following assisted conception had better survival rates in NICU. c Whereas preterm twins of 22–27 weeks, irrespective of the nature of conception, had higher mortality compared with singletons, mortality only diverges below 24 weeks’ gestation, at the very extreme of viability. Original article F20 Arch Dis Child Fetal Neonatal Ed 2010;95:F20–F24. doi:10.1136/adc.2009.157701