1. Centre of Excellence for Women and Child Health, Aga Khan University , Karachi 74800 , Pakistan
2. Department of Obstetrics and Gynecology, Aga Khan University , Karachi 74800 , Pakistan
3. Harvard T. H. Chan School of Public Health, Harvard University , Boston, MA 02115 , USA
4. Department of Paediatrics and Child Health, Aga Khan University , Karachi 74800 , Pakistan