Instead of saying:

"Those children, born later when the parents are in a more stable relationship and when their financial and social positions are more secure, will have, on average, a considerable advantage over the children who would have been born earlier."

think:

A woman who is not compelled to have a child she does not want, at a young age when she is emotionally and even physically immature and has not completed an education that will qualify her for employment with a decent income, is more likely to be poor and to suffer the physical and psychological effects of poverty that lead to a shortened life expectancy, and to be able to form a stable couple/family relationship that will provide all parties to that relationship, parents and children, with the social, economic, emotional and physical security that enhance their health and life expectancy.

The economic, social and health effects on the women of early childbearing by young single women are well known.

This is all part of the package of reasons why "the issue of outcome is nobody's business but the patient's and her doctor's, and the meddling outsider has no business sticking his/her nose into it." The same factors that operate in favour of the woman's future children operate strongly in her favour as well.

Everyone, including the society that has fewer women and children living in poverty and precarious relationships, benefits when women have control over their lives and bodies. But you are right to say that it is the woman's interests that prevail both in making the individual decision and in deciding whether to permit the decision to be acted on.

Quick google for early childbearing as a determinant of health ... this one refers to developing countries, but the factors apply everywhere.

http://www.worldbank.org/html/extdr/hnp/hddflash/issues/00060.html

These statistics show that investing in women at different stages of life could save millions of women in developing countries from needless suffering or premature death. However, the resources allocated for women's health do not reflect the clearly demonstrated need. For example, it is estimated that less than twenty percent of government health budgets are allocated to maternal and child health and family planning; most of which goes to child health. Poor health is a reflection of the low status of women in many developing countries. Some cultures can also limit a women's access to health services.

Women's health is affected by complex biological, social, and cultural factors. Therefore, to reach women effectively, policies and programs must take into account the biological factors that increase health risks for women and such sociocultural determinants of health as age at marriage and status in the family, as well as psychological factors, such as low self-esteem and depression arising from discrimination and gender violence. Women's lack of education and disadvantaged social position help perpetuate poor health and high fertility, as well as the continued cycle of poverty.

Because women tend to be less educated and have less access to information, they are less apt to recognize problems or understand the value of or seek out preventive and curative care. For example, female education, especially through the secondary level, is associated with greater use of contraception and increased age of marriage, both of which improve women's health by reducing their exposure to pregnancy and early child bearing.

A number of health problems associated with low socioeconomic status are emerging as concerns that need to be addressed by health and development programs. These include gender specific violence and occupational health hazards. In Papua New Guinea, for example, a Law Reform commission survey found that 67 percent of rural women were victims of wife abuse. Women's low status, particularly lack of education, exacerbated by economic hardship, is leading to increasing prostitution. This, in turn, is contributing to the rapid spread of sexually transmitted diseases, including AIDS.