London School of Hygiene & Tropical Medicine

Half of all babies who die in the first month of life are premature or born too small, with premature babies at the greatest risk of death, according to an analysis of studies in East Africa led by the London School of Hygiene & Tropical Medicine.

Every year around 3.3 million babies world-wide die within their first month of life, but the relative importance of low birth weight (less than 2,500 grams or 5.5 pounds), being born too small for gestational age (below the 10th percentile of weight for gestational age compared to a reference population), and preterm birth (less than 37 weeks gestation) in causing newborn deaths remains unclear.

To investigate these causes international researchers led by Dr Tanya Marchant analysed data on 4,843 live births from studies in Kenya, Tanzania, and Uganda. They found that overall, 9% of babies were low birth weight, 4% were premature, and 20% were small for gestational age.

In their detailed analysis published in PLoS Medicine, the authors found that the odds (chance) of death in the first 28 days of life were 7 times higher for low birth weight babies compared to those with normal birth weight. The odds of death were twice as high for babies born small for gestational age compared to those born appropriate weight for gestational age.  Compared to those born at term, the odds of death were over six times higher for babies born moderately preterm (between 34-36 weeks) and almost 60 times higher for babies born before 34 weeks—almost half of these babies died before they were one month old. Furthermore, moderately preterm babies who were also small for gestational age had a much greater odds of death than moderately preterm babies who were of the appropriate weight for gestational age.

Dr Marchant, Lecturer at the London School of Hygiene & Tropical Medicine, said: “Although preterm birth was the biggest risk factor for death, these findings suggest that small weight for gestational age also plays an important role, especially in moderately preterm babies. Babies born both moderately prematurely and small for gestational age made up 1% of the births, but 8% of the deaths we analysed. Extrapolating this percentage to the estimated 1.2 million newborn deaths each year in sub-Saharan Africa suggests that 96,000 African newborns who die each year are born both moderately premature and too small.

“These findings are important for public health because they emphasise the pressing need to find strategies that reduce foetal growth problems and prevent prematurity in Sub-Saharan Africa. Strategies could include tackling insufficient nutrition and the high infectious disease burden experienced by many women. This study provides evidence on which action to improve the situation can be based.”