Changing Survival Rate of Infants Born Before 26 Gestational Weeks Single-centre study

OBJECTIVES
This study aimed to evaluate the changing survival rate and morbidities among infants born before 26 gestational weeks at the Sultan Qaboos University Hospital (SQUH) in Muscat, Oman.


METHODS
This retrospective study assessed the mortality and morbidities of all premature infants born alive at 23-26 gestational weeks at SQUH between June 2006 and May 2013. Infants referred to SQUH within 72 hours of birth during this period were also included. Electronic records were reviewed for gestational age, gender, birth weight, maternal age, mode and place of delivery, antenatal steroid administration, morbidity and outcome. The survival rate was calculated and findings were then compared with those of a previous study conducted in the same hospital from 1991 to 1998. Rates of major morbidities were also calculated.


RESULTS
A total of 81 infants between 23-26 gestational weeks were admitted to the neonatal unit during the study period. Of these, 58.0% were male and 42.0% were female. Median gestational age was 25 weeks and mean birth weight was 770 ± 150 g. Of the 81 infants, 49 survived. The overall survival rate was 60.5% compared to 41% reported in the previous study. Respiratory distress syndrome (100.0%), retinopathy of prematurity (51.9%), bronchopulmonary dysplasia (34.6%), intraventricular haemorrhage (30.9%) and patent ductus arteriosus (28.4%) were the most common morbidities.


CONCLUSION
The overall survival rate of infants between 23-26 gestational weeks during the study period had significantly improved in comparison to that found at the same hospital from 1991 to 1998. There is a need for the long-term neurodevelopmental follow-up of premature infants.

2][3][4][5] The reasons for this improvement are multifactorial-technological advances, use of antenatal steroids, surfactant therapy, improvement in neonatal resuscitation and standard antenatal and postnatal care are major contributing factors.][11] Survival and short-and long-term morbidity rates are needed to determine if active perinatal management is rational for preterm infants born at or before 26 gestational weeks. 3The limits of viability and the gestational age at which a neonate can be resuscitated and supported are still a challenge in the Eastern Mediterranean region.Given the limited resources and infrastructure for supporting disabled children, it is very important to know the outcomes of extremely preterm infants in Oman.Sultan Qaboos University Hospital (SQUH) in Muscat, Oman, is a tertiary care centre with an obstetrics unit which accepts high-risk delivery cases from other health institutes in the country.The newborn service operates as a referral neonatal intensive care unit (NICU).A previous study from SQUH indicated much lower survival rates of extremely preterm infants born between 1991 to 1998 compared with other reports from developed countries. 9he aim of this study was to determine and evaluate the survival rate and morbidities of preterm infants at 23-26 gestational weeks at SQUH.These were then compared with the results of the study conducted in the same unit approximately a decade previously to ascertain the change in survival rate. 9Additionally, survival rates and common morbidities among the infants from the current study were compared with international data. 12,13

Methods
All premature infants born between 23-26 gestational weeks and admitted to the NICU at SQUH between June 2006 and May 2013 were included in the study.Infants referred to SQUH 72 hours or later after birth were excluded.Data were collected retrospectively from hospital electronic records, including maternal data, mode and place of delivery, antenatal complications, course of treatment during NICU stay and patient outcome (discharge or death).][16][17] Gestational age was determined from early ultrasound scans or calculated from the date of the last maternal menstrual period.Data were analysed using the Statistical Package for the Social Sciences (SPSS), Version 20 (IBM Corp., Chicago, Illinois, USA).Descriptive statistics and the incidence of neonatal mortality during the study period and among each gestational age group were calculated.For categorical variables, frequencies and percentages were reported.For numerical variables, the mean ± standard deviation or median and ranges were reported according to a normal distribution.A comparison of categorical data was performed using Chi-squared or Fisher's exact tests as appropriate.Numerical variables were compared using the Student's t-test for continuous data and the Mann-Whitney U test for non-continuous data.An a priori two-tailed value (P value) of ≤0.05 was considered significant.
Table 2 shows the demographic characteristics of preterm infants admitted to the NICU during the study period.Out of the 81 neonates, 47 were male (58.0%) and 34 were female (42.0%).The median gestational age was 25 weeks and the mean birth weight was 770 g.
The infants were assessed for common morbidities [Table 3].All of the infants were diagnosed with respiratory distress syndrome on the basis of clinical and radiological findings.A total of 37 infants (45.7%) received one dose of surfactant and 39 (48.1%) received two doses or more; five (6.2%) did not receive surfactant treatment.A total of 62 infants (76.5%) were screened for intraventricular haemorrhage (IVH) using cranial ultrasonography.Of these, 25 developed various degrees of IVH (seven neonates with grade I, five with grade II, four with grade III and nine with grade IV).A total of 10 infants (12.3%) developed necrotising enterocolitis while 17 (21.0%)and 11 (13.6%)infants developed moderate and severe    4].Among the fatality group, fewer infants received antenatal steroids (31.3% versus 67.3%; P = 0.001) and the mean birth weight was significantly lower (710 versus 810 g; P = 0.002) compared with the survivors.Gestational age was also lower in comparison with those who survived (24 versus 25 weeks; P <0.001).Apgar scores were significantly higher in the group that survived, both at one and five minutes (P = 0.014 and 0.029, respectively).Although pneumothorax and IVH occurred more frequently in the group of preterm infants who died, these differences were not significant.
Out of eight infants born at 23 gestational weeks, only one survived.Survival rates among the cohort at 24, 25 and 26 gestational weeks were 33.3%, 72.4% and 75.9%, respectively.These rates were compared with those from a multi-centre study performed by the Eunice Kennedy Shriver National Institute of Child Health & Human Development Neonatal Research Network (NICHD) in the USA as well as those reported in a previous study from SQUH [Table 5]. 5,9There were more hospital admissions of infants born <26 gestational weeks between 2006-2013 (n = 81) in comparison to 1991-1998 (n = 32). 9he overall survival rate for the present cohort had increased to 60.5% from 41%, the rate observed a decade previously at the same institution. 9There was an improving survival trend for infants of 24 and 26 gestational weeks.In the current study, survival rates for infants at 25 and 26 gestational weeks (72.4% and 75.9%, respectively) were comparable to those observed in the USA study (72.0% and 83.7%, respectively); however, decreased survival was noticed at 24 gestational weeks for the Omani infants at SQUH (33.3% versus 54.6%). 5Overall, survival rates increased with gestational age in both the comparative studies and present research. 5,9ommon short-term morbidities among the   6]. 12,13Incidences of bronchopulmonary dysplasia, severe IVH, necrotising enterocolitis and patent ductus arteriosus were comparable between the present study and the two international cohorts.

Discussion
8][19][20][21] The findings of this study indicated a significant increase in the number of admissions of infants born at <26 gestational weeks in comparison to a previous study conducted at the same institution. 9][7] Significant improvement was observed in the survival rate of preterm infants in Oman compared to hospital data from the 1990s. 9This may be due to specific institutional improvements in antenatal and postnatal care, staff training and subspecialty support as well as the modernisation of equipment and the implementation of standard international guidelines for the management of extremely premature infants.
One of the limitations of this study was that infants born between 22-24 gestational weeks who were not admitted to the NICU were not included in the sample.This is because it was difficult to retrieve these records retrospectively.However, all infants born at 25 and 26 gestational weeks were admitted to the NICU during the study period according to admission protocol.The exclusion of non-admitted infants between 22-24 gestational weeks may have resulted in a falsely low mortality rate in this cohort.Furthermore, this was a retrospective single-centre study with a small sample size; thus, the results cannot be generalised to all extremely preterm infants in Oman.The results of the current study provided information regarding mortality and the most severe short-term morbidities only.Long-term outcomes-including formal neurodevelopment follow-up data-for the survivors were lacking.Although major developmental delays are assessed in neonatal follow-up clinics, more resources are needed to ensure thorough follow-up of extremely preterm infants and thus assess the overall survival rate of this patient group.

Conclusion
The overall survival rate of extremely premature infants admitted to the NICU at SQUH improved significantly from a previous study at the same institution, suggesting an improvement in care.This study emphasises the need for long-term neurodevelopmental follow-up of this patient group in order to reveal the true clinical situation concerning preterm survival.c o n f l i c t o f i n t e r e s t The authors declare no conflicts of interest.

Table 4 :
Comparison of demographic and clinical characteristics of infants born before 26 gestational weeks by patient outcome (N = 81) Single-centre study e354 | SQU Medical Journal, August 2015, Volume 15, Issue 3

Table 5 :
Comparison of survival rates of preterm infants in Oman and the USA

Table 6 :
Comparison of morbidities of preterm infants in Oman with very low birth weight infants in the USA and Saudi Arabia