Prevalence and Outcome of Preterm Admissions at the Neonatal Unit of a Tertiary Health Centre in Southern Nigeria

Background: Preterm babies have increased risk of morbidity and mortality which is inversely related to both gestational age and birth weight. Most preterm births result from maternal or foetal medical conditions. Objectives: To determine the prevalence and outcome of preterm admissions at the Special Care Baby Unit of the Niger Delta University Teaching Hospital, as well as their morbidity pattern and risk factors for preterm birth. Methodology: All preterm babies admitted from January 2010 to December 2012 were retrospectively studied. Information obtained included gestational age at birth, sex, risk factors for preterm birth, duration of admission, medical problems during admission and outcome. Results: Preterm admissions constituted 24.0% of the total admissions with a male to female ratio of 1.1:1. The commonest risk factor for preterm birth was preterm rupture of foetal membranes (46.4%) followed by lack of maternal antenatal care (35.5%) and multiple pregnancy (26.8%) respectively. The commonest medical conditions were respiratory problems in 95 (68.8%) followed by jaundice in 94 (68.1%) and sepsis in 54 (39.1%) of the patients. The case fatality rate was highest in the patients with necrotizing enterocolitis and seizures (66.7%) followed by respiratory problems (63.2%) and bleeding disorders (60.0%). The overall survival rate was 65.9%. The survival rate was significantly higher in the mild preterm category compared to the very preterm and extremely preterm for birth categories χ2 = 29.24, p value = 0.000. Conclusion: Preterms constituted a significant percentage of neonatal admissions at the Niger Delta University Teaching Hospital with the case fatality being highest among those with infections and respiratory problems. There is an urgent need for the establishment of a neonatal intensive care unit with facilities for thorough evaluation and management of preterm babies in order to improve survival rate of this vulnerable group of patients. Corresponding author. O. E. Kunle-Olowu et al. 68


Introduction
Preterm birth defined as child birth occurring at less than 37 completed weeks or 259 days of gestation is a major determinant of neonatal morbidity and mortality with long term adverse health consequences [1]- [3].Infants born preterm compared to term infants experience more difficulty with feeding, blood glucose control, jaundice, temperature instability, apnoea, respiratory distress and sepsis either singly or in combination [4].Worldwide, preterm deaths constitute 28% of the 4 million annual new born deaths with 99% of these deaths occurring in developing countries [5].Morbidity, mortality and prolonged hospital stay of preterm babies result in significant cost to the health sector, parents and the society [6].In 2005, estimates done in the United States of America showed that the costs to the country in terms of medical and educational expenditure and lost productivity associated with preterm births were more than $26.2 billion [7].
With advances in Obstetric practice which have led to increased medical surveillance to identify and prevent progression of maternal and foetal complications, the incidence of preterm deliveries have also increased [8].In 2005, the World Health Organization (WHO) estimated 9.6% of all births worldwide to be preterm [9].Causal factors linked to preterm birth include medical conditions of the mother or foetus, genetic influences, environmental exposure, infertility treatments, behavioural and socio-economic factors as well as iatrogenic prematurity [10].According to Pennell et al. [11] approximately 45% to 50% of preterm births are idiopathic, 30% are related to preterm rupture of membranes and another 15% to 20% result from medically indicated or elective preterm deliveries.
Factors that influence the success in the management of prematurity include level of prenatal care, gestational age at birth, sex, availability of resources and adequate and well trained personnel [12].The evolution of neonatal intensive care is one of the recent advances that ensures survival of the preterm neonate but sadly this is not readily available in most developing countries [13].This is not surprising as neonatal intensive care is expensive because of the cost of sophisticated equipment, need for constant power supply, constant use of laboratory facilities and high staff to patient ratio [14].
It is necessary to carry out neonatal audit regularly as disease patterns vary from place to place and even from time to time in the same place [15].Though several studies [14] [16]- [18] have been done on preterm admissions in other parts of Nigeria, since the inception of the Niger Delta University Teaching Hospital (NDUTH) in 2007, there has been no study involving preterm babies.The present study was therefore carried out at the Special Care Baby Unit (SCBU) of the NDUTH, a tertiary health centre in Southern Nigeria with the aim of determining the risk factors for preterm births as well as the prevalence and outcome of preterm admissions, in order to contribute to existing data in the sub region and advise the hospital management in formulation of intervention plans to improve survival of this vulnerable group.Information derived from the study will also be used in public enlightenment campaigns on the prevention of preterm birth.

Study Centre
The study was carried out at the Special Care Baby Unit (SCBU) of the Niger Delta University Teaching Hospital (NDUTH), Okolobiri, Bayelsa State.The SCBU is the neonatal unit of the hospital where children less than 28 days are admitted.The unit has 6 cots and 3 incubators and is manned by 2 Paediatricians, Residents and-Nursing staff with an average ratio of one nurse to 6 patients.

Ethical Consideration
Ethical approval for the study was obtained from the research and ethics committee of the Niger Delta University Teaching Hospital Okolobiri, Bayelsa State.

Sampling
This was a retrospective descriptive study.Using the ward registers, the folder numbers of all preterm admissions over the 3 year period (January 2010 to December 2012) were obtained and the folders subsequently retrieved from the hospital records.All preterm babies in the SCBU of the NDUTH born at gestational ages of less than 37 completed weeks of gestation were included into the study while those born at or after 37 completed weeks were excluded.Information obtained from the folders include gestational age at birth, place of birth, sex, birth weight, risk factors for preterm birth, duration of hospital stay, medical problems during the period of admission and outcome.Parental educational status and occupation were also obtained and used to derive the parental social class according to Oyedeji's [19] classification.The gestational ages at birth were calculated using the first date of the mother's last menstrual period [20] or early pregnancy ultra sound scan [21].The birth weights were taken as the first recorded weight at birth for the in-borns or the weight on admission for those born outside the hospital and presented within the first 24 hours of life.The preterms were classified into 3 main categories according to gestational age at birth with those born from 32 to 36 weeks classified as mild preterms, 28 to 31 weeks very preterm and less than 28 weeks classified as extremely preterm for birth [22] [23].

Treatment Protocol
All preterm babies were admitted and cared for at the SCBU of the NDUTH.Those with weights less than 1800 g were nursed in the incubator, they were all given intravenous fluids, prophylactic phototherapy and intravenous antibiotics.They were fed with expressed breast milk from their mothers until they were mature enough to feed directly from their mothers breasts.Those who developed severe jaundice or bleeding disorders were managed with exchange blood transfusion in addition to phototherapy.They were weaned out of the incubator at weights equal to or greater than 1800 g if clinically stable.

Data Analysis
Data was entered onto an excel spreadsheet and presented as means and percentages in tabular form.Data was analyzed using SPSS version 15 statistical package.Test of significance between proportions was assessed using Chi-square at a 95% confidence interval with a p value of less than 0.05 considered statistically significant.

General Characteristics
During the study period, 634 babies were admitted into the special care baby unit (SCBU) of the Niger Delta University Teaching Hospital (NDUTH) of which 152 (24.0%) were preterm.One hundred and thirty eight (90.8%) of the preterm babies were studied as the other folders were either not found or had too many missing data.There were 71 males and 67 females with a male to female ratio of 1.1:1 (Table 1).
Their gestational ages at birth ranged from 24 to 36 weeks (Table 1) with a mean gestational age of 31.43 ± 3.65 weeks.Twenty three (16.7%) of the patients were born at 32 weeks gestation followed by 18 (13.0%)born at 28 weeks gestation.Most of the patients 129 (93.5%) were born between gestational ages of 28 and 36 weeks.
Their birth weights ranged from 700 g to 3200 g with a mean weight of 1626 ± 448 g.The mean birth weight increased with increasing gestational age from 950 ± 100 g in those born at 26 weeks gestation to 2291 ± 505 g in those born at 36 weeks gestation except in the 28 weeks, 33 weeks and 35 weeks gestational age groups respectively.
Sixty nine (50.0%) of the preterm babies were from the lower social class, 25 (18.1%) from the middle social class while 2 (1.4%) were of the upper social class.The social class of 42 (30.4%)babies could not be derived as a result of incomplete information in the case notes.
Thirty two (23.2%) of the babies were the first born of their mothers, 55 (39.9) were the second to fourth, while 35 (25.4%) were the 5 th or more.In 16 cases (11.6%), the birth order was not stated.

Risk Factors for Preterm Birth
As shown in Table 3, the commonest risk factor for preterm birth was preterm rupture of foetal membranes in 64 (46.4%) of the patients followed by lack of maternal antenatal care in 49 (35.5%) and multiple pregnancy in 37 (26.8%)respectively.

Morbidity and Mortality Pattern
The commonest medical conditions were respiratory problems in 95 (68.8%) followed by jaundice in 94 (68.1%) and sepsis in 54 (39.1%) of the patients (Table 4).
The case fatality rate was highest in the patients with necrotizing enterocolitis and seizures (66.7%) followed by respiratory problems (63.2%) and bleeding disorders (60.0%).

Clinical Outcome and Mean Duration of Stay according to Gestational Age
The duration of stay in the hospital ranged from 1 to 72 days with a mean duration of 13.33 ± 12.05 days.The mean duration of stay reduced with increasing gestational age from 18.25 ± 27.94 days in the 26 weeks gestational age group to 10.18 ± 6.90 in the 36 weeks gestational age group (Table 5).
Ninety one of the patients survived with an overall survival rate of 65.9%.The survival rate was 100.0% in the patients born at 33 and 36 weeks gestation respectively followed by those born at 35 weeks gestation with survival rate of 90.9%.

Survival Rate according to Category of Prematurity
As shown in Table 6, over half 74 (56.5%) of patients were mild preterms, followed by 14 (33.3%)very preterm and 9 (6.5%) extremely preterm for birth.The survival rate was significantly higher in the mild preterm category, followed by the very preterm category.This difference was statistically significant (χ 2 = 29.24,p value = 0.000).

Discussion
In the present study preterm admissions constituted 24.0% of all admissions at the special care baby unit of the NDUTH.This is less than the 16.4% reported by McGil Ugwu [24] at the Delta State University Teaching Hospital also in Southern Nigeria, but less than the 31.3% reported by Onwuanaku et al. [25] in Jos University Teaching Hospital, North Central Nigeria.The reason for these differences is not clear but may be due to differences in the incidence of preterm births in the various parts of Nigeria as a result of geographical and ethnic differences in these study populations.There is need for further studies on the influence of ethnicity and place of residence on the mean gestational age at birth.There were more preterm males than females in the present study compared to the study by McGil Ugwu [16] in Warri and Zeleke et al. [26] in Ethiopia who reported more preterm females.The commonest risk factor for prematurity was preterm rupture of foetal membranes followed by lack of antenatal care.This is similar to findings by Shrestha et al. [27] in Nepal who reported lack of antenatal care as the commonest risk factor for preterm births among their patients.Multiple pregnancy ranked third as a risk factor for preterm delivery in the present study.Other Nigerian authors [14] [18] [28] have also reported multiple pregnancy as a risk factor for preterm delivery.This is not surprising as multiple pregnancy has been shown to contribute to the increase in percentage of preterm births [8] with the average gestational age of twin birth being 35 weeks [29].The popular hypothesis is that multiple pregnancy causes over distension of the uterus which may stimulate premature uterine contractions resulting in preterm delivery [30] [31].
Hypertensive disorders in pregnancy were risk factors for preterm birth in almost a quarter of the patients in the present study.This is similar to reports from other authors in Nigeria [18] Nepal [27] and Thailand [32].Onyiriuka and Okolo [33] carried out a study on neonatal morbidity pattern in infants born in Benin City to Nigerian mothers with hypertensive disorders in pregnancy.They reported that the rate of preterm delivery was significantly higher in the hypertensive mothers compared to their normotensive counterparts.Hypertension in pregnancy is believed to predispose to acute or chronic utero-placental insufficiency resulting in antepartum and intrapartum foetal hypoxia with associated adverse outcomes of which preterm delivery is one [34].
Interestingly, abdominal massage also featured as a risk factor for prematurity in the present study.It is noteworthy that abdominal massage during pregnancy is common in the delta region of Nigeria where the present study was carried out [35].The popular belief is that abdominal massage loosens the nerves and relaxes the muscles thereby facilitating easy pregnancy and delivery as well as correcting malpresentation [35].This cultural practice however, has potentially harmful effects which include uterine rupture, abruptio placenta, premature rupture of foetal membranes, preterm labour and ruptured spleen [35].Igbarase GO [36] reported a case of maternal and foetal death from ruptured spleen as a result of abdominal massage at 30 weeks gestation in a rural community in the delta region of Nigeria.This highlights the urgent need for public enlightenment campaigns on the dangers of abdominal massage in pregnancy.
The commonest morbidity in the patients in the present study was respiratory problems followed by jaundice and sepsis.This is similar to reports by Khan et al. [37] in Karachi, Pakistan who reported jaundice and sepsis as the commonest morbidities in their preterm patients.Onalo and Olateju [38] in Abuja, Nigeria also reported jaundice as the commonest morbidity in their preterm patients.Onwuanaku et al. [25] in Jos University Teaching Hospital Nigeria, however reported sepsis as the commonest morbidity, followed by jaundice.This highlights the importance of infection control in the management of preterm babies who are a high risk group for neonatal sepsis as a result of their immature immune system [39].There is also an urgent need for the prevention and adequate management of jaundice in this vulnerable group.
The mortality rate in the present study was higher in the male preterms compared to their female counterparts which is similar to findings from other studies [16] [40].This is not surprising as male neonates, including preterms have been consistently reported to have higher mortality rates compared to their female counterparts [41] [42].In the present study, the duration of hospital stay increased with reducing gestational age.This may be explained by the fact that duration of hospital stay for specialized care is inversely proportional to gestational age as a result of associated illnesses and management requirements which increase with reducing gestational age [43].
The case fatality rate was highest in the patients with respiratory problems after necrotizing enterocolitis and seizures.Shrestha et al. [27] also reported respiratory problems as the commonest cause of death in their preterm patients.The overall survival rate was 65.9% with the survival rate improving with increasing gestational age and only one (11.1%) of the nine patients born at less than 28 weeks gestational age survived.This is not surprising as the average age of viability in Nigeria is still 28 weeks [17].The survival rate of preterms born at less than 28 weeks gestation in developing countries like Nigeria tends to be low as a result of unavailability of exogenous surfactant and mechanical ventilation [32].Kalimba and Ballot [44] in South Africa also reported a low survival rate of 26.5% in extreme low birth weight preterm babies who were not mechanically ventilated due to limited intensive care facilities.However 2007 reports in Netherlands, a developed country, showed that 52% of babies born between 23 and 27 weeks gestation survived to 2 years with 70.6% of them having no disability.Owa et al. [45] compared the birth weight and gestational age specific mortality rates among low birth weight infants at the neonatal units of Qatif Central Hospital, Saudi Arabia (with neonatal intensive care including 17 entilator support) and Wesley Guild Hospital, Ilesha, Nigeria (with only special care services but no 17 ventilator support).The overall mortality rate was lower in Qatif Central Hospital compared to Wesley Guild Hospital.This highlights the need for the establishment of neonatal intensive care units in developing countries like Nigeria with adequate equipment like portable x-rays and ventilators for more detailed evaluation and management of the extremely preterm for birth babies.
A limitation of the present study was that due to lack of sophisticated diagnostic facilities like portable xrays, cranial ultra sound scan and echocardiography, disease conditions like hyaline membrane disease, intra cranial haemorrhage and congenital heart disease were either under diagnosed or not diagnosed at all.Also as a result of late presentation to the hospital or incomplete information in the case notes, the gestational ages of some patients were unknown.

Conclusion
Preterms accounted for a significant percentage of neonatal admisions at the Special Care Baby Unit of the Nig-

Table 1 .
Gestational age and sex distribution.

Table 2 .
Place of delivery.

Table 3 .
Risk factors for preterm delivery.

Table 4 .
Morbidity and mortality pattern.

Table 5 .
Clinical outcome and mean duration of stay according to gestational age.
DAMA: discharged against medical advice.

Table 6 .
Survival rate according to category of prematurity.