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 Table of Contents  
Year : 2014  |  Volume : 11  |  Issue : 2  |  Page : 89-98

A prospective study of maternal risk factors for low birth weight babies in Maiduguri, North-Eastern Nigeria

1 Department of Obstetrics and Gynaecology, Aminu Kano Teaching Hospital, Kano, Nigeria
2 Department of Obstetrics and Gynaecology, University of Maiduguri Teaching Hospital, Maiduguri, Borno, Nigeria

Date of Web Publication6-Sep-2014

Correspondence Address:
Dr. Idris Usman Takai
Department of Obstetrics and Gynaecology, Aminu Kano Teaching Hospital, Kano, PMB 3452
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0331-8540.140353

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Background/Aim: Low birth weight (LBW) is associated with a higher risk of mortality and long term consequences for the survivors. This study determines the incidence and risk factors for LBW babies in Maiduguri. Context/Setting: This study was done in the Departments of Obstetrics and Gynaecology of the University of Maiduguri Teaching Hospital and the State Specialist Hospital, Maiduguri. Materials and Methods: This was a prospective study involving 854 pregnant women and their babies between 2 nd February 2009 and 29 th July 2009. Socio-demographic, obstetric, medical factors, obstetrics interventions and foetal birth weights were obtained and recorded. Association between variables were examined using student's t-test and Chi-squared test and multivariate logistic regression analysis a P < 0.05 was considered significant. Results: The incidence of LBW was 16.9%. The risk factors for LBW were non-use of haematinics index pregnancy (OR = 13.04; 95% CI = 12-36; P value 0.000); previous history of stillbirth (OR = 8.11; 95% CI = 6-19; P value 0.000); hypertensive disorders of pregnancy (OR = 6.12; 95% CI = 5-14; P value 0.000); ante-partum haemorrhage (OR = 5.85; 95% CI = 4-9; P value 0.000); less than 4 ANC visitsn (OR = 4.94; 95% CI = 3-12; P value 0.000); previous history of premature delivery (OR = 4.39; 95% CI = 4-11; P value 0.000); previous history of LBW (OR = 3.65; 95% CI = 2-21; P value 0.000) and non-use of intermittent preventive therapy in the index pregnancy (OR = 3.24; 95% CI = 1-16; P value 0.001); and teenage mother (OR = 2.75; 95% CI = 2-27; P value 0.006). Conclusion: This study showed high incidence of LBW. Obstetric factors (problems and intervention of the current pregnancy) and previous obstetric performances played crucial role in the occurrence of LBW in our study. Qualitative antenatal care should be made available and provided to pregnant women at all levels of care.

Keywords: Incidence, low birth weight, Maiduguri, Nigeria, risk factors

How to cite this article:
Takai IU, Bukar M, Audu BM. A prospective study of maternal risk factors for low birth weight babies in Maiduguri, North-Eastern Nigeria. Niger J Basic Clin Sci 2014;11:89-98

How to cite this URL:
Takai IU, Bukar M, Audu BM. A prospective study of maternal risk factors for low birth weight babies in Maiduguri, North-Eastern Nigeria. Niger J Basic Clin Sci [serial online] 2014 [cited 2021 Aug 4];11:89-98. Available from: https://www.njbcs.net/text.asp?2014/11/2/89/140353

  Introduction Top

According to World Health Organization (WHO), a new born baby weighing less than 2500 g at birth with the measurement taken within 24 hours of life, before significant weight loss has occurred, is designated as low birth weight (LBW) baby. [1],[2] Many infants in developing countries are not weighed at birth because many births take place at home without the assistance of skilled health personnel. [1] In Nigeria today, a high proportion, [two third], [3] of births take place at home outside health facilities and only 35% of births are attended by skilled health personnel. [4] Logistic difficulties in recording birth weight at home will therefore preclude accurate national estimates of the magnitude and trends of LBW. However, a large volume of data on birth weight is available from individual studies, most of which are hospital based. [3] LBW can arise as a result of a baby being born too soon (at less than 37 weeks, also known as preterm birth) and/or being born too small for gestational age (small as a result of intrauterine growth restriction). [1],[2] Babies that are born prematurely and are also small for their gestational age have the worst prognosis. Weight at birth is considered one of the most important indicators of a newborn's chances of survival, growth, long-term health and psychosocial development, with LBW being a major risk factor for perinatal and infant mortality. [5] Those who survive are more likely to remain malnourished, have impaired immune function and face increased risk of health and developmental problems including lower intelligent quotients and cognitive disabilities leading to learning difficulties, school failure and poor job opportunities. [5] They are also prone to hearing and visual impairments, chronic respiratory problems such as asthma and chronic diseases such as non-insulin dependent diabetes mellitus (NIDDM) and coronary heart disease and stroke later in life. [1],[2],[5],[6] Thus, the baby born with a birth weight under 2500 g could be an 'at risk' individual for life! [1]

WHO and UNICEF published the first global, regional and country estimates of LBW incidence in 1992. [7] At that time the LBW incidence for industrialized countries was around 7% and in less developed countries, it ranged between 5- 33% with an average of 17%. [7] In fact, the latest projections indicated that more than half (72%) of the world's LBW babies are born in South Asia alone and some 13-15% born in Sub-Saharan Africa. [1],[6] According to WHO the incidence of LBW is estimated to be 14% worldwide [1] and is the same with the Nigerian National figure of 14%. [1] Neonatal death in Nigeria also contributes about 25% of the total infant mortality with prematurity and LBW being the main contributors to these high neonatal deaths. [8] However, there is significant variation in LBW incidence across the main geographic regions of the world, ranging from 4-45%. [1],[9] The incidence of LBW is 27% in South Asia followed by West and Central Africa (15%), East and Southern Africa (14%), Middle East and North Africa (12%). Among the more developed regions, Latin America and Caribbean averaged 9%, while East Asia and Pacific has the lowest regional average at 6%. [1]

In Nigeria, there is considerable variation within the country in the incidence of LBW as reported in hospital based studies ranging between 8-12%. [10] An earlier study in the University of Maiduguri Teaching Hospital (UMTH), Maiduguri, reported an incidence of 5.75%, [11] and LBW babies accounted for 41.1% of perinatal mortality [12] in a similar study in the same centre. In a recent study in Lagos, [13] an incidence of 10.2% was reported. In Enugu, the study showed a significantly higher incidence in LBW babies in 1998 as compared with the incidence in 1984. The babies were on average 183 g heavier in 1984 than in 1998, [14] this was felt to be as a result of the decline in socio-economic status of average Nigerians. An incidence of 8.3% was reported from a study in Ibadan, [15] while an incidence of 18.2% (males) and 20.8% (females) [16] was reported in a series from Ilorin. Rehan and Tafida, [17] in a study of LBW in Hausa babies in Katsina, Northern Nigeria, reported an incidence of 21.3%. In a review of neonatal morbidity and mortality in Aminu Kano Teaching Hospital, Kano, LBW accounted for 32.1%. [18] A study from Jos, in middle belt region of Nigeria, and consisting of a heterogeneous population of tribes, has reported an incidence of 12.7%. [19] At the University of Benin Teaching Hospital (UBTH), Benin City, an incidence of 3.4% was reported, [20] and in a similar study from a missionary hospital in Benin City, it revealed an incidence of 8.1%. [21] In a recent community based study from Nnamdi Azikiwe University, Awka, an incidence of 45% [22] was reported.

In the developing world, LBW stems primarily from poor maternal health and nutrition. [23] Giving birth to a LBW baby is influenced by several determinants including maternal variables, [23],[24] like maternal age (<20 or >35 yrs), ethnicity, marital status, birth interval, educational level, inadequate antenatal weight gain. Environmental factors, paternal factors (e.g. paternal height), foetal or placental factors resulting in an impaired placental transport of nutrients or reduced growth potential of the foetus are other determinants. [23],[24] A variety of maternal socioeconomic, socio-demographic, physiologic, pathologic and psychosocial factors are also known to increase the risk of low birth weight. [2],[23],[24],[25],[26] Constitutional, gender and hereditary factors explain up to 40% of the variability of birth weight. [26] Medical risk factors for LBW before pregnancy are chronic conditions like hypertension, renal insufficiency, cardio-respiratory, autoimmune, endocrine or infectious disorders. The risk factors for LBW during pregnancy are hypertensive disorders, diabetes, malnutrition, bleeding, anaemia, infection, placental or foetal anomalies and multiple pregnancies. In addition, a heavy physical workload during pregnancy may also negatively impact birth weight. [25],[26],[27]

The contributions of LBW on perinatal outcome cannot therefore be over-emphasized. LBW can results in high financial costs to the country's health sector and a serious burden on the immediate family, health care givers and the community in general. The entire extended family are worried and depressed, seeing their newborn baby covered in a machine in the neonatal intensive care unit (NICU). Studies conducted by Patwari [11] and Idrissa [12] in UMTH about 21 years ago, found a LBW incidence of 5.75% and a perinatal mortality rate of 22.6% in which LBW babies accounted for 41.1% of the perinatal death. To our knowledge, these were the last studies carried out in this environment which are related to the present study. These are against the backdrop of the hard and declining socio-economic realities of recent times as a whole within this period, emergence of new diseases like HIV, compared to the relatively prosperous economy of the 1980s when these studies were carried out. [28] These studies were retrospective in nature and only privileged neonates in the middle and upper socio-economic class were included. Therefore the population studied may not be a representative of the population of Maiduguri. The true incidence of LBW and risk factors for LBW for Maiduguri newborn babies will therefore be known only if a representative sample is studied. This is what the present study aims to achieve by including the State Specialist Hospital (SSH) Maiduguri, which cater for the majority of the poor. Evidence is accruing indicating that these LBW are caused by factors that are potentially modifiable or most of which can be prevented. [1],[4],[5],[7] The costs of preventing them are well within reach, even in poor countries and developing countries like ours. An understanding of the prevalence and a risk factors and constant surveillance of LBW is therefore of utmost importance and any abnormality, when detected should allow for intervention by the authority concerned. The aim of the study was to determine the incidence of LBW, and to determine the risk factors associated with LBW babies delivered in Maiduguri.

  Materials and Methods Top

This was a prospective cohort study. The study was done in the Departments of Obstetrics and Gynaecology of UMTH and SSH, Maiduguri from February 2 nd 2009 to July 29 th 2009. All aspects of the study were reviewed, authorised and approved by the research and ethical committee of the hospitals (UMTH and SSH) Maiduguri. Borno State occupies the greater part of the Chad Basin with an area of 116,589 km 2 . It is situated in the North-Eastern Sub-region of Nigeria. The state shares borders with the Republic of Niger to the North, Chad to the North-East and Cameroon to the East. Within Nigeria, Borno State shares boundaries with Adamawa State to the South, Gombe State to the West, and Yobe State to the North-West. The Northern part of the state is covered by Sahara Desert, with an exceptional small belt near the Lake Chad. The Southern part of the state contains the Biu Plateau, and slightly northeast of the plateau is the mountainous area of Gwoza and Askira/Uba.

Maiduguri is the capital of Borno State and has a population of about 521,492 according to the 2006 population census. [29] Maiduguri is a cosmopolitan city with the Kanuris, Bura, Shuwa-Arab, Marghi, Gwoza, Fulani, Hausa, Igbo and Yoruba as the major residents. There are also settlers from neighbouring francophone countries of Chad, Cameroon and Niger Republics. Like other cities in Nigeria, Maiduguri has all the facilities like hospitals, colleges, University, airport etc., The main food consumed by the people includes cereals, tubers, vegetables, fruits, fish, meat and meat products among others. The socio-cultural background of the people is similar, with Islam and Christianity as the major religions.

The study population included all pregnant women who gave their consents, booked and delivered in the UMTH and the SSH and their live singleton newborns. We excluded all pregnant women who declined consent, multiple gestations, gross congenital malformation at birth or diagnosed antenatally and still born baby. Unbooked mothers with known last menstrual period were later included 2 weeks after the expected date of delivery of the enrolled mothers ('considered defaulters or lost to follow‐up') to complete the sample size. The estimated number of pregnant women that attends UMTH per month was given as 2342 (statistic unit of the medical record department). A minimum sample size was calculated using a standard formula for a known population size given below. [30]

Where n = sample size of adjusted population, n = population size and e = accepted level of type one error of 5%, and a study power of 80%.

Substituting the figures into the formula above, the minimum sample population required was estimated at 854 pregnant women for the two health facilities.

These patients who consented and met the inclusion criteria were then recruited for the study. Informed verbal and written consent to participate in the study was obtained from each patient recruited for the study. Sampling was done by convenience sampling through approaching all women who satisfied the inclusion criteria during the weekly booking clinic until the required sample size was obtained. Those enrolled were followed up till delivery. The questionnaires used for this study were pre-tested at UMTH using a few respondents. Interviewer administered questionnaires were used to obtain socio-demographic, obstetrics and medical information. The questionnaires were not translated to respondents' vernacular; however help was given to some of the women in the interpretation of the questionnaires especially those who could not speak English. Mother's age, educational level, occupation, ethnic group, marital status, address, parity, duration of pregnancy (in weeks) and birth-to-pregnancy interval (as duration in months between the immediate previous birth and conception of current pregnancy as stated by the mother) were obtained. Histories of miscarriage, preterm birth, stillbirth, previous LBW, smoking or eating of Kola nut (traditionally called 'Gorongo', bitter or the conventional ones) during the pregnancy were also obtained. Similarly, history of treatment of malaria in the index pregnancy and history of chronic medical conditions (hypertension, diabetes, sickle cell anaemia, asthma, heart disease and chronic renal disease and HIV status) were ascertained. Patients had basic booking examinations (except otherwise) including general physical examination, weight, height, blood pressure, obstetrics examinations. A predesigned proforma and the booking cards were used to record these information and labelled with the patient's identification number and followed up until patient presented in labour. To complete the booking process, investigation forms were given to each recruited patient for packed cell volume, blood group and Rhesus typing, haemoglobin genotype, Veneral disease research laboratory test (VDRL), urinalysis for albumin and glucose. Ultrasound scanning (Micromaxx ultrasound system 2D, made by SonoSite, USA) was offered to the study population. Voluntary counselling and testing for HIV with opt out option was also offered to all women. Haematinics were given routinely to all women while tetanus toxoid immunization was given as indicated. Intermittent preventive treatment (IPT) with suphadoxine-pyramethamine combination was given at booking (after 16 weeks or after quickening) and repeated 4 weeks from the first dose but before 36 weeks of pregnancy. HIV positive mothers had three doses of the IPT. The women continued their antenatal care (ANC) and were seen according to their appointments.

When patients presented in labour, a packed cell volume (PCV) and urinalysis was done for all patients in labour. Gestational age (GA) (in weeks) was assessed by calculating the number of completed weeks of gestation since the beginning of the last menstrual period (LMP). Early (<20 weeks) ultrasonic measurements were also considered in the assessment of GA. Patients were fully examined, including general physical examinations, systemic examination, obstetric examinations and vaginal examination. Labour allowed to progress, monitored in accordance to standard protocol and delivery conducted. The babies were fully examined, including general physical examination, suctioning and cleaning, APGAR scoring, gender assignment, birth weight, birth length and head circumference. Birth weight (in grams) was measured by trained midwives or doctors without clothes within the first 1 hour of delivery, using a standard baby weighing scale (Baby Weigh TM Scale, manufactured by MedelaR Inc. model 040.7012 which has an accuracy rate of 0.034-0.042%). A birth weight of <2500 g = LBW; 2500-3999 g = normal birth weight (NBW) and ≥4000 g = high birth weight (HBW). Babies were then broadly grouped into either LBW or Not LBW (NBW + HBW). To minimize errors in measurements, scale was always checked and zeroed before weighing. Record review format was used for reviewing ANC cards for use of haematinics and other supplements, use of anti-malarial prophylaxis during pregnancy and attendance at ANC and recorded. All information were entered in to the patient's proforma already prepared at booking. The volunteer clinicians for this study assisted in collecting data as per their usual shifts. All the information required were actually filled on the questionnaire within 24 hours of delivery. The principal investigator ensured that the data obtained were from the study subjects and correctly filled.

Simple descriptive univariate analysis was performed to determine the frequency of the various factors. Means and standard deviations for continuous variables were computed. Bivariate analysis was used to examine the associations of individual factors with LBW and stepwise multivariate logistic regression analyses were used to evaluate the effects of the independent correlation of each factor on LBW rate by estimating odds ratios and their 95% CI. The model used an entry criterion of P = 0.05. A P <0.05 was considered significant. Results were presented by simple statistical tables.

  Results Top

The subjects were 854 mothers (720 booked and 134 unbooked considered 'defaulters or lost to follow‐up') and their 854 live singleton babies. There were 460 (53.9%) male and 394 (46.1%) female babies. Among these babies, 144 (16.9%) were LBW. Six hundred and sixty (660) had NBW whereas HBW was seen in 50 babies. The incidence of LBW was 16.9%. The preterm delivery rate was 80.6% (116) among the LBW babies. The mean GA at delivery was 38.5 ± 1.7 weeks. The incidence of preterm delivery in the entire study population was 24.9% (213), yet it accounted for 80.6% of the LBW babies, while term delivery was 75.1% (641) and accounted for 19.4% (IUGR-LBW). Thus GA at delivery significantly influenced the occurrence of LBW (χ2 = 2.86; df; =1; P value 0.000). The incidence of LBW was higher in males(8.7%) than in females (8.2%), but this was not statistically significant (χ2 = 0.427; df; =1; P value = 0.513). These are shown on [Table 1]. Among all births, the small-for-GA (SGA) babies were 11%; large-for-GA (LGA) babies were 28% while appropriate-for-GA (AGA) babies accounted for 61%.
Table 1: Gestational age and infant's sex distribution by birth weight categories

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[Table 2] shows the influence of maternal socio-demographic factors on incidence of LBW. The mean maternal age was 26.6 ± 6.0 years. Most (69%) of the mothers were 20-34 years old at the time of their child's birth, while 12% were aged 35 years or older. The incidence of LBW babies was highest (30.3%) among teenage mothers but it decreased significantly with increasing maternal age to 10.7% in those aged 35 years and above (χ2 = 25.35, df; =2; P value 0.000). Other maternal socio-demographic factors that were significantly associated with LBW included maternal education (P value 0.000), maternal occupation (P value 0.000), and marital status (P value 0.003). However, religion and ethnicity had no significant influence on the occurrence of LBW (P value 0.31 and P value 0.07) respectively. None of our respondents smoked cigarette or took alcoholic beverages. However, significantly more women who ate Kolanut had LBW babies (24.7%) compared with those who did not (15.9%) (χ2 = 4.37; df; =1; P value 0.036).
Table 2: Influence of maternal socio - demographic factors on incidence of LBW

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[Table 3] shows the effect of maternal obstetric factors/interventions on incidence of LBW. The mean parity was 2.2 ± 2.3 (range 0-14). There was inverse relationship between parity and LBW (P value 0.001). There were significant associations between booking status (P value 0.000), number of ANC visits (P value 0.000), regularity of visits (P value 0.002) and LBW. The mean GA at booking was 25.9 ± 6.1 weeks. As is seen from the table, majority (55.1%) of the mothers booked in the third trimester and even though early registration influenced the occurrence of LBW, this was not statistically significant (χ2 = 3.05; df; =2; P value 0.217). Short birth-to-pregnancy interval, bad obstetric history, previous history of LBW, and premature delivery were all significantly associated with LBW (P value 0.000). There were significant association in mothers who had any form of vaginal bleeding in the index pregnancy (P value 0.000), the use of haematinics (P value 0.000) and IPT (P value 0.000) with sulphadoxine-pyrimethamine combination for prophylaxis against malaria in the index pregnancy and occurrence of LBW.
Table 3: Effect of maternal obstetrics factors/interventions on incidence of LBW

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The effect of maternal medical factors on incidence of LBW is shown on [Table 4]. Anaemia at booking was significantly associated with occurrence of LBW (χ2 = 7.80; df; =1; P value 0.005) and the strength of association between anaemia and incidence of LBW was maximum (30.8%) with anaemia in labour (χ2 = 92.40; df; =1; P value 0.000). Sickle cell anaemia, asthma and hypertensive disorders of pregnancy were similarly associated with LBW (P value 0.000). However, none of the five diabetic mothers had LBW babies in this study. Maternal infections (HIV and Malaria) significantly influenced the occurrence of LBW (P value 0.000) in this study. There was no significant association between HIV positivity, treatment with anti-Retroviral drugs and occurrence of LBW (P value 0.066).
Table 4: Effect of maternal medical factors on incidence of LBW

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In summary, bivariate analysis taking LBW as the dependant variable and each of the study variables as the independent variables revealed that preterm delivery; Low maternal age; Mother's illiteracy level; Unemployment; Unmarried status; Consumption of Kolanut; Primigravidity; Unbooked status; <4 ANC visits; Irregular ANC visits; Short birth-to-pregnancy interval of <18months; History of miscarriage; History of stillbirth; History of LBW; History of premature delivery; Non- use of haematinics; Non-use of IPT; Any form of vaginal bleeding in the index pregnancy; Anaemia at booking; Anaemia in labour; Sickle cell anaemia; Asthma; Hypertensive disorders of pregnancy; HIV infection and Malaria infection contributed significantly to the occurrence of LBW. Variables found significant by bivariate analysis were entered into the multiple logistic regression analysis models in step-wise manner, with LBW as the dependent variable together with risk factors as predictors or independent variables and then run. The independent variables were those with a threshold statistical significance level of <0.05. The final model for the prediction of LBW consisted of 9 variables; as presented in [Table 5]; thus multivariate analysis revealed that the acceptable predictors of LBW in our population are:
Table 5: Multivariate logistic regression analysis of the risk factors of low birth weight babies in Maiduguri

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  • Non- use of haematinics in the index pregnancy (OR 13.04, 95% CI: 12-36, P value 0.000)
  • Previous history of stillbirth (OR 8.11, 95% CI: 6-19, P value 0.000)
  • Hypertensive disorders of pregnancy (OR 6.12, 95% CI: 5-14, P value 0.000)
  • Vaginal bleeding in the index pregnancy (OR 5.85, 95% CI: 4-9, P value 0.000)
  • Less than 4 ANC visits (OR 4.94, 95% CI: 3-12, P value 0.000)
  • Previous history of premature delivery (OR 4.39, 95% CI: 4-11, P value 0.000)
  • Previous history of LBW (OR 3.65, 95% CI: 2-21, P value 0.000)
  • Non-use intermittent preventive therapy (OR 3.24, 95% CI: 1-16, P value 0.001)
  • Teenage mothers (OR 2.75, 95% CI: 2-27, P value 0.006).

This study evaluated and analyzed the incidence and risk factors for LBW babies in Maiduguri, Borno State, North-Eastern part of Nigeria. The incidence of LBW of 16.9% in this study is comparable with the WHO/UNICEF reported global, regional and country observed incidences of 14%, and also similar to 13-15% reported for Sub-Saharan Africa. [1],[6] It also compares well with the 17% reported for the least developed and developing countries, [7] and lies within the global observed variations of 4-45% within the main geographical regions of the world. [1],[9] Our finding was however almost three times higher than the 5.75% reported in the same locality, [11] over two decades ago, and also higher than incidences reported across the country. [13],[14],[15],[19],[20],[21] It is lower than some figures reported from other studies in the country. [16],[17],[18],[22] The higher incidence observed in our study may be partly due to the fact that, this study included complicated pregnancies and the inclusion of the State Specialist Hospital Maiduguri, the largest referral centre owned by the State Government which cater for the majority of the poor. It could also be explained by the fact that there is increase awareness of the pregnant women to health needs created during antenatal classes, and increase public awareness through the media. Similarly, available statistics show that the reproductive health situations in Borno state is worst compared to other part of Nigeria, [3],[31] and this might have led to the higher incidence of LBW observed in this study. In fact, it has been reported that more than one third of the population of Nigeria live in extreme poverty-defined by the World Bank as earnings of under $1 per day; while 9 out of 10 Nigerians live on less than $2 per day. [28] The zones in the northern part of the country where this study was carried out present the highest vulnerability, with highest proportion of the households experiencing chronic poverty. [28] The hard and declining socio-economic realities of Nigerians in recent times, emergence of new diseases like HIV, compared to the relatively prosperous economy of the 1980s when the study in the same locality was carried out, [28] in which only the privileged neonates in the middle and upper socio-economic class were included, might have also contributed to the higher incidence of LBW recorded in this study. The previous study in this locality was a retrospective one in which some data may not be readily available for analysis. There is also some evidence to suggest that the higher incidence of LBW babies born in developing countries reflect, in fact, adverse environmental influences before and during pregnancy which result in majority of SGA babies, [6] and this may be a reflection in the study environment. Efforts are therefore required to reduce the incidence detected by the current study to improve pregnancy outcome. Better understanding of causes and risk factors for LBW will help in preventing and reducing the incidence of LBW.

Our study has shown that the identified risk factors for delivering LBW baby operational in our population are: teenage, less than four ANC visits, previous history of stillbirth, previous history of premature delivery, previous history of LBW, non-use of haematinics in the index pregnancy, and non-use of intermittent preventive therapy. Maternal medical factors/obstetric complication as the risk factors included hypertensive disorders of pregnancy, and ante-partum haemorrhage. It is now universally acknowledged that maternal age is an important factor influencing the incidence of LBW. [1],[13],[23],[25],[26] In the present study, teenage mothers who comprised only 18.1% of the subjects are responsible for the highest (30.3%) incidence of LBW and were also found to be 2.7 times more likely to have LBW babies than mothers who were aged 20 years and above. The finding on age is in keeping with what was reported in the same environment over two decades ago, [11] and also compares well with other studies. [13],[15],[16],[20],[21],[22] A possible explanation is the fact that in Maiduguri, like other cities in the North, neither stigma nor favour is attached to teenage pregnancy and girls get married at very early age before they are fully matured which can be explained by various religious, social and cultural reasons. [11] Age at first birth may also be a marker for low socio-economic status. [3],[4],[6],[13],[22],[31] Good Nutrition and education of girl-children is paramount in this regards. Women should therefore be empowered at all levels, this will go a long way in reducing the higher incidence of LBW observed in this age‐group.

The study has shown that the association between number of ANC visits and the incidence of LBW was statistically significant, similar findings were observed by various other studies that showed the risk of LBW was lower among those who had four or more ANC visits in comparison to mothers who received less than four ANC visits. [1],[6],[13],[21],[22] The study showed that mothers with <4 ANC visits were 4.9 times more likely to deliver a LBW baby compared to mothers with >4 ANC visits. It has been observed that most women in Maiduguri, Nigeria are not booked, avoid hospital deliveries and prefer home deliveries with the help of TBAs. [3],[31] The birth weights of these babies are usually not recorded in hospital register, thus even if they are of LBW, they will not be identified. In developing countries, prenatal care, even if only attended once, remains an important factor in obstetric care, as this may be a critical linkage between the women with maternity care services. [13] In contrast, research findings in middle-income countries emphasize the importance of the number of prenatal care visits and the adequacy and quality of prenatal care services. WHO technical working group committee has recommended four ANC visits for a woman with normal pregnancy and recommends prenatal care as a strategy for improved obstetric care. [1],[4] Our data suggested that prenatal care may help ensure that interventions occur in a timely manner, thus those mothers at risk for LBW can be identified early enough if good and qualitative prenatal care is made available to them.

Maternal antenatal complications such as malaria and anaemia which are known to predispose to LBW babies are common in Nigerian obstetric practice. [9],[20],[22],[32] Substantial iron deficiency anaemia (usually <80 g/l) is associated with an increased incidence of LBW. The mechanism by which anaemia could produce this effect is unknown, but other nutrient deficiencies are important contributing factors. [23],[24] In this study, the incidence of LBW among women who did not use haematinics or any other supplements such as folic acid and multivitamins during pregnancy was significantly higher than those who used it. More mothers who did not use IPT with sulphadoxine-pyrimethamine combination for prophylaxis against malaria during pregnancy delivered LBW babies. This finding agrees well with other reports. [13],[15],[22],[32],[33],[34],[35] The regression model has shown that mothers who did not use haematinics in the index pregnancy and those that did not use IPT for malaria prophylaxis were associated with an excess risk of 13 and 3 times of delivering a LBW baby than mothers who used haematinics and IPT respectively. A 1.9 excess risk in non-users of haematinics during pregnancy was reported from Iran. [36] Anaemia and malaria in pregnancy have deleterious effect on both maternal and perinatal outcome and iron supplementation and intermittent preventive therapy of malaria have been shown to reduce the untoward effects of these disease conditions. [32],[33] The problems of anaemia and malaria are very important reproductive health issues in our country and should not be ignored, thus pregnant mothers should be encouraged as much as possible to use haematinics and IPT in order to reduce the risk of delivering LBW baby. Recent studies on prophylaxis against malaria using tablets or bed nets have shown a trend towards a higher mean BW among those in the protected groups. [22],[32],[33],[34],[35] Women, who had bad obstetrics history, were significantly associated with higher incidence of LBW and this finding was in agreement with other studies. [34],[35],[36] The study showed that these mothers were 8.1 times more likely to deliver LBW babies than mothers without such history. Mothers with previous history of LBW were 3.7 times excess risk of having LBW compared to mothers without previous history and this was similar to what was observed by Shiva et al., [37] who found an excess risk of 4, and a 2.5- fold was reported from Iran, [38] but lower than Mansour et al., [39] who found that the history of giving birth to a LBW baby increases the chance of delivering LBW baby three times our findings. This disparity may be as a result of large sample size and inclusion of stillbirth, multiple pregnancies and congenital malformations in their study. It is possible that multiple aetiologic factors that affect neonatal weight are generally the same in all pregnancies of the same mother. Prematurity significantly influenced the occurrence of LBW. This finding agrees well with previous studies. [34],[35],[37],[39] Perhaps genetic and socio-economic factors were the operational reasons for this phenomenon leading to repeat adverse obstetric outcome. Therefore improvement in socio-economic status may likely lead to better pregnancy outcome.

Hypertensive disorders of pregnancy, was the single most important risk factor for LBW among the studied maternal medical disease. It increased the risk of LBW by 6.1 folds in our study in keeping with a finding of 6 folds from a study by Singh et al., [34] however, other studies reported a 40.9 folds, 2 folds, 3.7 folds and a 4.6 folds, increase in some population. [19],[36],[37],[38] More mothers with hypertensive disorders of pregnancy delivered LBW babies, in consonance with some reports. [13],[19],[20],[34],[37],[38] Hypertension causes blood vessel stenosis in pregnant women, reduces plasma volume, reduces the supply of nutrients to the foetus thus affecting foetal growth and results in LBW. [2],[5],[27] Complications during pregnancy such as placenta abruption and placenta praevia have been directly associated with LBW. [39] Maternal pregnancy complication such as ante partum haemorrhage which is known to predispose to LBW babies is common in Nigerian obstetric practice. [13],[20] In our study, there was a 5.9 fold increase risk in delivering LBW in mothers with ante-partum haemorrhage, consistent with a 5.4 folds increase risk in a study from Egypt. [37]

Based upon the findings of this study, there is the need to provide qualitative ANC services at all health care levels and possibly strengthen the existing maternal health care services in the state. Pregnancy amongst teenagers may be concealed and they do not present for ANC. Health promotion in this regards should be targeted to this age‐group. Improving the socio-economic status especially of women is therefore essential. Periodic evaluation of the risk factors for LBW to reduce its burden to the barest minimal is recommended. Our study has some limitations. The associations we established in the predisposition and/or risk factors for LBW in this study, could be confounded by unmeasured factors. Some maternal febrile co-morbidities like urinary tract infection (UTI) in pregnancy, tuberculosis (TB) and premature rupture of membranes (PROM) which are known to predispose to LBW [18],[32],[34] were not studied. TORCHES are some important foeto-maternal infections associated with LBW babies, [36] placental factors and uterine malformations were all beyond the scope and ability of this study. Poor precision (nearest 50 g) of spring type of weighing scale used in our study is another limitation, though daily checking and zeroing the weighing scale before new measurements may eliminate some errors, there could have been some intra-observer error in measurements. Since this study was carried out on a sample of newborn babies in a hospital setting, generalisation of the findings to the entire community may be limited. Community-based studies are advocated and may overcome this limitation.

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  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5]

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