title: Independent and joint effects of prenatal Zinc and Vitamin A Deficiencies on birthweight in rural Sidama, Southern Ethiopia: prospective cohort study.
abstract: BACKGROUND
  The effects of prenatal Zinc Deficiency (ZD) and Vitamin A Deficiency (VAD) on birthweight are controversial and their interaction has not been investigated.
  
  
  OBJECTIVE
  To assess the independent and interaction effects of prenatal zinc and vitamin A deficiencies on birthweight in rural Sidama, Southern Ethiopia.
  
  
  METHODS
  A community-based prospective cohort study design was employed. Six hundred fifty pregnant women in their second or third trimester were randomly selected and their serum zinc and retinol concentrations were determined. About 575 subjects were successfully followed until delivery and birthweight was measured within 72 hours after delivery. The association between the exposures and birthweight was examined using log-binomial and liner regression analyses. Potential interaction between ZD and VAD was examined using Synergy Index (SI).
  
  
  RESULTS
  The mean birthweight (± standard deviation) was 2896 g (±423). About 16.5% (95% CI: 13.5-19.6%) of the babies had Low Birthweight (LBW). Prenatal ZD and VAD were not significantly associated to LBW with Adjusted Relative Risk (ARR) of 1.25 (95 CI: 0.86-1.82) and 1.27 (95% CI: 0.86-1.87), respectively. Stratified analysis on the basis of gestational trimester showed that the occurrence of the deficiencies neither in the second nor third trimester were associated to LBW. The deficiencies did not show synergetic interaction in causing LBW [SI = 1.04 (95% CI: 0.17-6.28)]. Important risk factors of LBW were maternal illiteracy [RR = 1.80 (95% CI: 1.11-2.93)], female sex of the newborn [RR = 1.79 (95% CI: 1.19-2.67)], primiparity [RR = 1.16 (95% CI: 1.02-1.35)], short maternal stature [RR = 1.63 (95% CI: 1.06-2.51)] and maternal thinness [RR = 1.52 (95% CI: 1.03-2.25)]. In the linear regression model, elevated CRP was also negatively associated to birthweight.
  
  
  CONCLUSIONS
  LBW is of public health significance in the locality. The study did not witness any independent or interaction effect of prenatal ZD and VAD on birthweight.
authors.affiliation: College of Agriculture, Hawassa University, Hawassa, Ethiopia. samsongmgs@yahoo.com
authors.forename: Samson
authors.initials: S
authors.lastname: Gebremedhin
authors.forename: Fikre
authors.initials: F
authors.lastname: Enquselassie
authors.forename: Melaku
authors.initials: M
authors.lastname: Umeta
mesh_terms: D000328:Adult; D001724:Birth Weight; D002097:C-Reactive Protein / Q000096:biosynthesis; D015331:Cohort Studies; D005002:Ethiopia; D005260:Female; D006801:Humans; D008297:Male; D018811:Maternal Exposure; D011247:Pregnancy; D011248:Pregnancy Complications / Q000453:epidemiology; D011446:Prospective Studies; D012044:Regression Analysis; D012424:Rural Population; D012923:Social Class; D013997:Time Factors; D014802:Vitamin A Deficiency / Q000175:diagnosis*; D015032:Zinc / Q000172:deficiency*
chemical_list: D002097:C-Reactive Protein; D015032:Zinc