title: Does the Mother or Father Determine the Offspring Sex Ratio? Investigating the Relationship between Maternal Digit Ratio and Offspring Sex Ratio.
abstract: OBJECTIVE
  In mammals, high parental testosterone levels present around the time of conception are thought to skew offspring sex ratio toward sons. The second to fourth digit ratio (digit ratio) is now widely accepted as a negative correlate of prenatal testosterone. Thus, we investigated the association between digit ratio and offspring sex ratio.
  
  
  METHODS
  A total of 508 Korean patients (257 males and 251 females) less than 60 years old who had one or more offspring were prospectively enrolled. The lengths of the 2nd and 4th digits of the right hand were measured by a single investigator using a digital vernier calliper. Next, the patients' lifetime offspring birth sex ratios were investigated.
  
  
  RESULTS
  Maternal (rather than paternal) digit ratio was significantly associated with the number of sons (r = -0.153, p = 0.015), number of daughters (r = 0.130, p = 0.039), and offspring sex ratio (r = -0.171, p = 0.007). And, the maternal digit ratio was a significant factor for predicting offspring sex ratio (B = -1.620, p = 0.008) on multiple linear regression analysis. The female patients with a lower digit ratio (< 0.95) were found to have a higher offspring sex ratio (0.609 versus 0.521, p = 0.046) compared to those with a higher digit ratio (≥ 0.95). Furthermore, females in the low digit ratio group have a probability 1.138 greater of having sons than females in the high digit ratio group.
  
  
  CONCLUSIONS
  Maternal digit ratio was negatively associated with offspring sex ratio. Females with a lower digit ratio were more likely to have more male offspring compared to those with a higher digit ratio. Thus, our results suggest that the sex of offspring might be more influenced by maternal rather than paternal factors.
authors.affiliation: Department of Urology, Gachon University Gil Hospital, Incheon, Republic of Korea.
authors.forename: Tae Beom
authors.initials: TB
authors.lastname: Kim
authors.affiliation: Department of Urology, Gachon University Gil Hospital, Incheon, Republic of Korea.
authors.forename: Jin Kyu
authors.initials: JK
authors.lastname: Oh
authors.affiliation: Department of Urology, Gachon University Gil Hospital, Incheon, Republic of Korea.
authors.forename: Kwang Taek
authors.initials: KT
authors.lastname: Kim
authors.affiliation: Department of Urology, Gachon University Gil Hospital, Incheon, Republic of Korea.
authors.forename: Sang Jin
authors.initials: SJ
authors.lastname: Yoon
authors.affiliation: Department of Urology, Seoul National University Hospital, Seoul, Republic of Korea.
authors.forename: Soo Woong
authors.initials: SW
authors.lastname: Kim
mesh_terms: D000328:Adult; D005220:Fathers; D005260:Female; D005385:Fingers / Q000033:anatomy & histology*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D009035:Mothers; D011336:Probability; D012307:Risk Factors; D012744:Sex Ratio