title: Finger Length Ratio (2D:4D) in Central India and an Attempt to Verify Fraternal Birth Order Effect: A Population Based Cross-Sectional Study.
abstract: BACKGROUND
  A normal physiology of a human being is not mere a series of functions occurring with specific intensities and timing. There are lot of factors that may change the normal physiological activity within normal limits. Finger length ratio is one of the markers of intrauterine androgen exposure and it is debated and contradicted by many authors. Digit ratio varies among the ethnicities. Many Indian studies show that there is considerable difference in finger length ratio in different population. Data regarding Central India was not found on extensive search.
  
  
  OBJECTIVE
  To find out the finger length ratio and explore the birth order effect on finger length ratio among the first two successive born in the said population.
  
  
  METHODS
  We conducted a survey on 1500 volunteer persons (800 male and 700 female) over two years of time. We measured the length of the index finger (2D) and ring finger (4D) of both the hands and asked about their birth order history to find out the digit ratio for Central India population and any existing correlation of the same with birth order. T Test and Analysis of Variance (ANOVA) were used for the measure of significance and difference among the groups. The p< 0.05 was considered to be significant.
  
  
  RESULTS
  Our study reports that, study population mean for right hand 2D:4D ratio was 0.976 (SD±0.031) and for left hand it was found to be 0.969 (SD±0.035). For males, mean finger length ratio for right hand was 0.967 (SD±0.033) and 0.963 (SD±0.037) for left hand. In females the mean Finger length ratio was 0.982 (SD±0.027) for right hand and 0.974 (SD±0.034) for the left hand respectively. Finger length ratio was found to be significantly less (p=0.03) in males for right hand. No significant (p=0.24) difference was observed for left hand. When assessed fraternal birth order effect among the eldest, second born with elder brother and second born with elder sister groups, no significant (p>0.05) variation for finger length ratio of right and left hands observed in both male and female population.
  
  
  CONCLUSIONS
  Our study reports that the finger length ratio (2D:4D) for Central India population did not show significant association between finger length ratio and fraternal birth order among the first two successive born.
authors.affiliation: Assistant Professor, Department of Physiology, Modern Institute of Medical Sciences , Kanadia Indore, Madhya Pradesh, India .
authors.forename: Arjun
authors.initials: A
authors.lastname: Maitra
authors.affiliation: Assistant Professor, Department of Biochemistry, Modern Institute of Medical Sciences , Kanadia Indore, Madhya Pradesh, India .
authors.forename: Chaitali
authors.initials: C
authors.lastname: Maitra
authors.affiliation: Professor and Head of Department, Department of Physiology, Sikkim Manipal Institute of Medical Sciences , Tadong Gangtok, Sikkim, Assam, India .
authors.forename: Dilip Kumar
authors.initials: DK
authors.lastname: Jha
authors.affiliation: Professor, Department of Medicine, L.N. Medical College and Research Centre , Bhopal, Madhya Pradesh, India .
authors.forename: Rakesh
authors.initials: R
authors.lastname: Biswas
keywords: Digit ratio; H-Y antigen; Prenatal androgen exposure; Sex dimorphism