La Constitución de 2008 en relación al tema de estudio

Study Site

The study was a prospective case control study conducted at the Maternity Hospital Wing of the University of Ilorin Teaching Hospital, Ilorin.

Ilorin is the capital of Kwara State with a population of 572 178 and an annual population growth rate of 2.3%. The State has a total population of 1 566 469 (projected from 1991 census). Vegetation is Guinea savanna.¹⁶⁹

The maternity hospital wing of the hospital provides secondary and tertiary healthcare services in neonatology, obstetrics and gynaecology. It caters for patients from Kwara State and parts of Oyo, Osun, Niger, Kogi and Ekiti states.

The department of Obstetrics and Gynaecology attends to both booked and unbooked emergency cases. The annual delivery rate is 2000 to 2500. Deliveries are both vaginal (spontaneous and assisted) and operative.

The neonatal intensive care unit (NICU) provides level II care to both inborn and out born neonates. It admits between 1000 and 1200 patients annually. All high risk deliveries taking place in the maternity wing are attended to by a paediatric resident.

Sample Size

The minimum sample size for the study was estimated using the formula n = z²pq ¹⁷⁰

d² Where

n = minimum sample size

z = normal standard deviation for 95% confidence p = estimated prevalence of preterm delivery q = 1.0 - p

d = tolerable margin of error set for the purpose of the proposed study at 5%

For this study, sample size was calculated based on prevalence of preterm delivery reported by Ibhanesebhor et al¹⁸ from Benin.

z = 1.96 (at 95% confidence level)

p = 6.2% (prevalence of preterm delivery) q = 1.0- 0.062=0.938

d = 0.05

n = 1.96²×0.062×0.938 0.05²

= 89

Allowing an attrition rate of 10%, the minimum sample size estimated was 99 preterm babies.

However, all deliveries during the period of subject recruitment were recorded in order to provide a denominator for calculating the incidence of preterm delivery and comparison of outcome measures. They were also used as controls particularly in determining the maternal socio-biologic characteristics associated with preterm deliveries.

Ethical Clearance

Ethical clearance was obtained from the Ethics Review Committee of the hospital (appendix V). The project was clearly explained to the mother and/ or father (appendix I) in a language they understand before subject recruitment. One of them

either signed or used the left thumb to thumb print the informed consent form (appendix II).

College Approval

Approval was obtained from the National Postgraduate Medical College of Nigeria to proceed with the field work.

Subject Recruitment

Subjects were recruited consecutively until the desired sample size was achieved. Two times the minimum estimated sample size was recruited to increase the power of the study. All deliveries during the study period were recorded consecutively. Following recruitment, the deliveries were grouped into preterm deliveries and term deliveries.

Recruitment of subjects was done by the Principal Investigator (PI) and/or trained Paediatric Residents assisting the investigator.

Inclusion Criteria

1. All deliveries in the maternity hospital wing of the UITH during the study period.

Exclusion Criteria

1. Subjects unsure of their LMP.

2. Discrepancy greater than 2 weeks between gestational age determined by LMP and that from Ballard assessment.

3. All multiple gestations.

4. All babies with gross congenital malformations.

5. All post term deliveries.

Data Collection

A structured study proforma (appendix III) was administered on all subjects recruited. Data on maternal profile collected include maternal age, tribe, height, parity, antenatal status, ante partum haemorrhage, previous preterm delivery, previous abortion and drug intake during pregnancy. Data on weight at first antenatal care visit, packed cell volume and pregnancy induced or associated hypertension was obtained from the mother's hospital records. Maternal body mass index was determined only for those who booked during the first trimester of pregnancy. It was determined using the formula weight (kg)/height (m)². Socio-economic index scores were awarded to the subjects based on the occupations and educational attainments of their parents or caregivers using the Oyedeji socio-economic classification scheme¹⁷¹(Appendix IV).

The mean of four scores (two for the father and two for the mother) approximated to the nearest whole number was the social class assigned to the subject.

All babies were allocated Apgar scores at one and five minutes by the investigator.¹⁷² Those with scores below 7 were allocated extended Apgar scores at intervals of 5 minutes up to 20 minutes or until the child attained a score of 7, whichever occurred first while resuscitation continued.

A thorough examination was done on all recruited subjects. This enabled identification of congenital malformations and documentation of morbidities. Two methods of estimating gestational age were employed, the date of mother’s last menstrual period and the Ballard score.¹⁰⁴ For uniformity, the gestational age derived from the Ballard score was used for analysis. Subjects were excluded when the mother was unsure of the date of her last menstrual period or when there was an

irreconcilable discrepancy in the gestational age by LMP and Ballard > 2 weeks. The weight was measured with the baby nude using a bassinet weighing scale (Waymaster). The scale was adjusted to zero before the baby was weighed. The weight was measured to the nearest 50g. The scale was checked for accuracy with standard weights every month. The length was measured with an improvised infantometer. With the child supine on a flattened firm surface, the feet were put together and held against a fixed foot piece, the back was straightened and the head was aligned to form a continuous longitudinal line with the back and lower limb. The fixed foot piece formed the zero mark. A movable head piece was placed firmly against the vertex and the readings were measured to the nearest 0.5cm. The occipito-frontal circumference was measured with a non stretchable tape measure. The measurement was taken at the maximum point of occipital protuberance posteriorly and at a point one inch above the glabellar anteriorly. The measurement was taken to the nearest 0.5cm. With an odd shaped or an abnormally large head, the maximum size of head circumference was obtained. The measurements obtained were plotted on a Lubchenco chart²¹ and the babies were classified as LGA, AGA, or SGA. The respiratory rate, heart rate and temperature were recorded. Congenital anomalies identified were documented. All babies were managed according to standard protocol depending on symptomatology and diagnosis. Morbidities encountered like sepsis, anaemia, apnoea, necrotizing entero-colitis, respiratory distress, asphyxia and jaundice were recorded. Duration of admission for both survivors and those that died was also recorded. Relevant details of clinical course and cause of death in fatal cases were recorded.

Data Analysis

Data from the proforma were entered into personal computer using SPSS version 11.0 for windows software. The data was cleaned before analysis. Frequency distribution tables for variables were generated. Prevalence of preterm delivery was determined. Potential determinants of prematurity and outcome were cross tabulated and odd ratios with their 95% confidence interval determined. Student t test and Mann-Whitney U test were used to test to test the significance of continuous variables. Chi- square test (with Yates correction where applicable) and Fisher’ss exact test were used to test for significance of the differences between categorical variables. The contributions of multiple independent variables on a specific outcome variable were determined using linear logistic regression analysis. Level of significance was put at 0.05.