Standard birth weight by gestational age values is not available for Sub-Saharan Africa. Still, they are needed to assess the incidence and risk factors for intrauterine growth retardation in areas where HIV, antiretrovirals, and other in utero exposures may impact birth outcomes. Researchers gathered data on birth weight was from six Botswana hospitals. They used the birth weight of infants born to HIV-negative women between 26 and 44 weeks of pregnancy to create gestational age charts. They matched these findings to published American norms for black newborns.

Birth records from 6 Botswana hospitals and clinics were evaluated in real-time over 29 months from 2007 to 2010. The study looked at 11,753 live babies who were born to HIV-negative mothers. The median birth weight was 3100 grams, while the median gestational age was 39 weeks (1st quartile 38, 3rd quartile 40 weeks). Researchers created approximated percentile curves for birth weight by gestational age, which show an increasing slope during the third trimester and a plateau after 40 weeks. Botswana-born newborns had a lower median birth weight for gestational age from weeks 37 to 42 (p <.02) than black infants in the United States. 

They report Botswana’s birth weight for gestational age norms, which are lower at term than US norms for black infants. These findings suggest the importance of regional birth weight norms in identifying and defining risk factors for higher-risk newborns. They use the data to identify infants at risk for perinatal problems and compare newborns exposed to HIV and antiretrovirals in utero. They can also compare infants exposed to HIV and antiretrovirals in utero.