Sex ratio of male sex preselected children born to couples with exclusively female offspring.

The present study was undertaken to determine if couples with exclusively female children had a decreased probability of a male child after using male sex preselection. Selection criteria for subjects necessitated that couples have had only female children previously and had produced a child at one of 14 centers after using protocol 3 (n = 70) and modified 3 (n = 28) male sex preselection. Prior to sex selection, protocol 3 couples produced a combined total of 135 female children for an average of 2.01 (range 1-4) females per couple; modified 3 couples produced a combined total of 62 female children for an average of 2.21 (range 1-4) females per couple. The normal approximation to the binomial distribution was used to determine significant differences between the sex ratios prior to and after male sex preselection. For couples using protocol 3 there were significant differences in the sex ratio prior to sex preselection (0%) and after sex preselection (73.0%) (p less than .00003). There were also significant differences between the sex ratio prior to modified 3 (0%) and after sex preselection (86%) (p less than .00003). Couples using male sex preselection do not have a decreased probability of a male child if they have had exclusively female children.