English: The chart shows male to female sex ratio for India based on its Census data, along with historical timeline of technology for fetal sex determination ultrasonography.

Data sources:

1. 1941 through 2001 data is from Page 3, Chapter 6, "Sex Composition of the Population", Census of India 2001, Series 1, Paper 1 of 2001 (Publisher: Office of Registrar General and Census Commissioner of India, Ministry of Home Affairs, Government of India). Web version: http://censusindia.gov.in/Data_Products/Library/Provisional_Population_Total_link/PDF_Links/chapter6.pdf

2. Sex ratio for 2011 is from Final Population Totals, "Sex Composition of the Population", Census of India 2011 (Publisher: Office of Registrar General and Census Commissioner of India, Ministry of Home Affairs, Government of India). Web version: http://censusindia.gov.in/2011census/censusinfodashboard/

3. Historical timeline for ultrasonography in prenatal, obstetrics and gynecology is from: (a) Joseph Woo, A short History of the development of Ultrasound in Obstetrics and Gynecology; (b) "Looking at the Unborn: Historical Aspects of Obstetric Ultrasound" - Witness seminar transcript. Wellcome Witness to Twentieth Centurty Medicine. E M Tansey, D A Christie (editors), January 2000; (c) Roger Freeman et al. (2012), Fetal Heart Rate Monitoring, 4th Edition, ISBN 978-1451116632, Chapter 1, pages 2-4.