An unmatched case-control study was conducted among women who delivered in five referral hospitals in the Western Area Urban district of Sierra Leone to determine factors associated with delivery of low birth weight (LBW) babies. This study has identified some socio-demographic, socio-economic, obstetric and lifestyle-related factors that are associated with the delivery of LBW babies in the study area.
Earlier studies from across Africa have reported some association between the delivery of LBW babies and several maternal socio-demographic, socio-economic, obstetric and medical factors [12–14]. In our current study, mothers who were unemployed were found to have a two-fold odds of giving birth to a LBW baby. This is consistent with findings of a population-based study in southern rural Ghana, which established a strong association between birth weight and maternal employment status. Mothers who were unemployed and coming from the poorest households were reported to be more likely to give birth to LBW babies compared to those who were gainfully employed . Unemployment can contribute to poverty, leading to poor maternal nutritional intake . According to Ahmed, et al., maternal undernutrition and inadequate dietary diversity during pregnancy are significant determinants of delivery of low birth weight babies .
The odds of delivering a LBW baby as observed in the current study, was greater among mothers who were anaemic during pregnancy (Hb < 11.0 g/dl), compared to those who were not, similar to an earlier study also carried out in Ghana . Other studies done in Ethiopia , Democratic Republic of Congo  and India  have also reported similar findings in which anaemia during pregnancy was found to be associated with LBW. Anaemia during pregnancy can limit maternal oxygen uptake, thus reducing oxygen supply to the foetus and this contribute to foetal growth restriction .
In this study, babies born within less than two years after another child had higher odds of being of LBW, compared with those born after two or more years. Similar findings have been reported from Ethiopia [18, 19] and India . This might be as a result of insufficient replacement of maternal nutrients used-up during the previous pregnancy and this may lead to reduced foetal development. A similar observation made in South Ethiopia by Mingude, et al.  has been explained on the basis that, the short inter-pregnancy interval is not able to allow the mother enough time to recover from the nutritional burden and stress of the previous pregnancy, resulting in maternal nutrition depletion. The short inter-pregnancy interval is also associated with maternal iron and folic acid depletion . This reduces the ability of the mother to support foetal growth and development which in turn increases the possibility of growth restriction and LBW in subsequent pregnancies.
Our study also revealed that mothers who smoke cigarettes have higher odds of giving birth to a LBW baby. In a similar case-control study conducted in China , pregnant women who were exposed to even passive smoking had an increased risk of delivering low birth weight babies. Although, our study failed to determine the number of cigarette sticks smoked per day and for how long, other studies have reported that, mothers who are heavy smokers (> 8–10 cigarettes/day) had a higher odds of LBW babies . Cigarette smoking is known to reduce oxygen supply to the foetus in-utero as carbon monoxide and nicotine-associated vasoconstriction reduces uterine and placental blood flow, thereby restricting the growth of the foetus, and hence can contribute to LBW . Other factors including gravidity, maternal ill-health and taking of herbal medicine during pregnancy were not found to be significantly associated with the delivery of LBW babies in the current study after multivariable logistic regression analysis.
Although we employed a case-control study, which we consider an appropriate design for the study, the study is not without limitations. Assessment of some independent variables was liable to recall bias. The measurement we used for maternal smoking may not be the most suitable. Measuring the number of cigarettes sticks smoked by a mother in a day may better show the difference between the cases and controls. These limitations notwithstanding, the study has identified important maternal factors that when addressed, can reduce the incidence of LBW deliveries in Sierra Leone and other developing countries with similar characteristics.