填空题 If mothers could choose the sex of their children, a disproportionate number of boys would undoubtedly be (31) at first but the sex ration at birth would ultimately even out. (32) to new findings of a national survey released yesterday.
The survey (33) questioned 5981 married women (34) their sex preferences in children, indicated that most would prefer their first-born to be a boy (35) by a girl (36) the second child.
Thus, in the United States at least, the survey indicates that counter to the fears of some, the ability to select the sex of offspring would not greatly distort the ultimate sex ratio of the population.
The survey findings, a part of the 1970 National Fertility Study, also (37) that (38) the time they were questioned, at least half of currently married women (39) to leave sex selection to nature (40) than use some new technology to predetermine the (41) of their children.
The National Fertility Study, first done in 1966, is based (42) national random sample of married women under 45 years of age living in the United States.
If left to (43) the national sex ratio (44) birth is 105 boys to 100 girls, with an approximately equal chance that a family with two children would have the following combinations: boy-girl, girl-boy, boy-boy or girl-girl.
The survey findings, published in the current(May 10) (45) of the journal Science, indicate that (46) sex selection were readily available and widely used, (47) would be a temporary"20 per cent excess of male births. "This would occur mainly (48) most women who have not yet had children would select a boy as their first-born, giving a birth ratio of 189 boys to 100 girls.
Then, as these women select girls as their second child, the sex ratio would ultimately balance out. Among women who have already started their families, the survey showed that in subsequent births they would seek to balance the sexes of their children, (49) would have little if any effect (50) the national sex ratio.