BIRTHS TO UNMARRIED MOTHERS ARE at a record high in the United States--almost 1.5 million in 2004 alone, according to the National Center for Health Statistics. While the rising trend is of long standing, one novel factor driving up childbearing outside marriage is the growing popularity of single motherhood by donor insemination. The incidence of this "assisted reproduction," as it is called, has more than doubled in the last decade.Most public discussion of donor insemination for single women has been carried on in a neutral, positive, or breathlessly celebratory tone. Isn't it great, the thinking seems to be, that these...