This summer, President Obama proclaimed again that we “need fathers to recognize that responsibility doesn’t end at conception.” In a sense, of course, he is absolutely right. But the problem is that, in another sense, he is completely wrong: Male responsibility really does end at conception. Men these days can choose only sex, not fatherhood; mothers alone determine whether children shall be allowed to exist. Legalized abortion was supposed to grant enormous freedom to women, but it has had the perverse result of freeing men and trapping women.

The likelihood of this cultural development was foreseen by the radical feminist Catherine MacKinnon, one of the critical voices responding to Roe v. Wade’ s extension of the right of privacy to cover abortion. In an essay called “Privacy vs. Equality,” MacKinnon argued that “abortion’s proponents and opponents share a tacit assumption that women do significantly control sex. Feminist investigations suggest otherwise. Sexual intercourse . . . cannot simply be presumed coequally determined.” Indeed, she added, “men control sexuality,” and “ Roe does not contradict this.”

“Abortion facilitates women’s heterosexual availability,” MacKinnon pointed out: “In other words, under conditions of gender inequality [abortion] does not liberate women; it frees male sexual aggression. The availability of abortion removes the one remaining legitimized reason that women have had for refusing sex besides the headache.” Perhaps that is why, she observed, “the Playboy Foundation has supported abortion rights from day one.” In the end, MacKinnon pronounced, Roe ’s “right to privacy looks like an injury got up as a gift,” for “virtually every ounce of control that women won” from legalized abortion “has gone directly into the hands of men.”

At the time, MacKinnon’s work may have seemed little more than a curiosity on the left, but, as the years have passed, some of the essay’s claims have proved prescient. I recall a law student who would admit when pressed, “I’m in favor of keeping abortion legal because I don’t like using condoms.” Since abortion could now come between conception and birth, he saw no benefit to missing any portion of sexual pleasure, even though it imposed a risk of surgery on his partner. He may have assumed a rational partner would choose abortion either freely or under pressure. With less deliberate callousness, under the influence of passion almost any male may think quite simply: “At least there’s a way out if the unlikely happens and pregnancy occurs.”

I’ve also met a clever female undergraduate student living with her boyfriend, who thought she had solved this problem. When I asked whether she was for or against abortion, she answered: “I’m pro-choice, but you can bet I tell him I’m pro-life!” She reasoned that, in light of her warning, he would be careful not to fool around in ways that could lead to pregnancy.

Such a lie may not provide protection for every young woman in her situation, however. If she says she is pro-life so that he thinks abortion is not an option for her, he might decide to keep her from getting pregnant by leaving her for someone more open to abortion, a woman who doesn’t insist on his using a condom. That is, the presence in the sexual marketplace of women willing to have an abortion reduces an individual woman’s bargaining power. As a result, in order not to lose her guy, she may be pressured into doing precisely what she doesn’t want to do: have unprotected sex, then an unwanted pregnancy, then the abortion she had all along been trying to avoid. Even though her abortion in this case is not literally forced, it would be, in an important sense, imposed on her. And, far from alleviating her overall situation, it would merely return her to the same sexual pressures, made worse by a new assurance to her boyfriend that she is willing to take care of a ­pregnancy.

Perhaps it was difficult to foresee such cultural trends back in 1973, when Roe v. Wade was handed down by the Supreme Court. But they simply track the inner logic of choice and the market. Economists have shown that such scenarios have in fact become common since abortion was legalized in the United States. Easy access to abortion has increased the expectation and frequency of sexual intercourse (including unprotected intercourse) among young people, making it more difficult for a woman to deny ­herself to a man without losing him, thus increasing pregnancies and sexually transmitted infections. (See, for instance, Jonathan Klick and Thomas Stratmann’s 2003 study, “The Effect of Abortion Legalization on Sexual Behavior,” in the Journal of Legal ­Studies .)

Furthermore, if a woman attempts to choose birth instead of abortion, she may well find the child’s father pushing the other way. Her boyfriend’s fear of fatherhood would once have been focused on intercourse itself and could have led him either to be careful to avoid conception or else (overcoming that fear) to commit himself beforehand to equal responsibility for the child. His fear now will turn to getting her to choose abortion. One investigator, Vincent M. Rue, reported in the Medical Science Monitor , that 64 percent of American women who abort feel pressed to do so by others. Another, Frederica Mathewes-Green in her book Real Choices , discovered that American women almost always abort to satisfy the desires of people who do not want to care for their children.

Catherine MacKinnon seemed to suggest that abortion leads to greater male sexual aggression only “under conditions of gender inequality,” which implies more equality for women could reduce the male exploitation caused by Roe v. Wade . That makes sense in theory. To the degree that individual women are economically, educationally, and in other ways empowered, they should be more able to stand up to male pressures to have unwanted sex (and to have unwanted abortions in order to give the guys still more unwanted sex).

But counteracting the negative forces of sexual competition is difficult. Even if women were universally to agree to refuse sex without condoms, for example, enforcement of this agreement in such an intimate sphere would be nearly impossible. Women would always be tempted to increase their individual sexual competitiveness by consenting to sex without a condom, while relying on abortion as a backup, thus causing female solidarity and power to collapse. Only women strong enough to forgo boyfriends altogether might be likely in the end to resist.

Furthermore, if MacKinnon is right, wherever women have not yet overcome gender inequality, involuntary sex and involuntary abortion will tend to be more frequent, precisely as a result of abortion’s availability. To the degree that a culture is built on machismo, for example, the legalization of abortion will make women relatively worse off by giving men another tool to manipulate women as sex objects. Again, to the degree that an economy employs mainly men, leaving women dependent on economic handouts, women will be much less likely to resist male pressures to make use of abortion. Wherever men make women’s decisions for them, the option of abortion will be a man’s choice, regardless of how the law may label it.

Human-rights activists in developing nations must learn to consider this fact. In those countries, only a thin, elite layer of truly independent and powerful women may be relatively unharmed by the availability of abortion, because only for them is the abortion option more nearly their own. Proclaiming a right to abortion in developing countries may mean just adopting the viewpoint of these well-to-do professionals”which ought to be no surprise. Those elites are often the only voices for women heard in the transnational political arenas where abortion is debated.

Moreover, the availability of abortion may make all societies less open to empowering women in other ways. MacKinnon may well be right that stronger women would more often resist male pressures to risk pregnancies and have abortions. But, perhaps paradoxically, the option of abortion actually makes sympathy and solidarity”and thus women’s empowerment”less likely.

When birth was the result of passion and bad luck, some people could sympathize with a young woman who was going to need help with her baby, though the stigma of bastardry was genuine. If money or a larger place to live were going to be necessary for her to stay in school, a sense of solidarity would likely lead friends and family to offer assistance. The father would feel strong pressure as well, for he was as responsible as she for the child. He might offer to get a second job or otherwise shoulder some of the burdens of parenting.

But once continuing a pregnancy to birth is the result neither of passion nor of luck but only of her deliberate choice, sympathy weakens. After all, the pregnant woman can avoid all her problems by choosing abortion. So if she decides to take those difficulties on, she must think she can handle them.

Birth itself may be followed by blame rather than support. Since only the mother has the right to decide whether to let the child be born, the father may easily conclude that she bears sole responsibility for caring for the child. The baby is her fault.

It may also seem unfair to him that she could escape motherhood (by being legally allowed to prevent birth), while he is denied any way to escape fatherhood (by still being legally required to pay child support). If consenting to sex does not entail consenting to act as a mother, why should it entail consenting to act as a father? Paternity support in this context appears unjust, and he may resist compliance with his legal duties.

Prior to the legalization of abortion in the United States, it was commonly understood that a man should offer a woman marriage in case of pregnancy, and many did so. But with the legalization of abortion, men started to feel that they were not responsible for the birth of children and consequently not under any obligation to marry. In gaining the option of abortion, many women have lost the option of marriage. Liberal abortion laws have thus considerably increased the number of families headed by a single mother, resulting in what some economists call the “feminization of poverty.”

The mother is even worse off if, during pregnancy, tests show that the child will have a disability: Doctors often press for abortion, in order to be sure that she does not later blame and sue them for the costs of raising her child. Some have suggested that health-care plans should provide no postbirth coverage for a handicapped child whose mother refuses a paid abortion. If she does not abort, after all, she will be causally responsible for the costs and the alleged burdens that the child brings. Even her friends and neighbors may make her feel ashamed for not choosing to abort her child.

Employers may likewise react negatively to maternal needs where abortion has been available. If they (or the state) pay for abortions, they may feel less obligated to shape labor practices to the needs of mothers. If maternity causes problems with work routines or job schedules, the employer may well consider these to be private or personal problems that female employees brought on themselves. The availability of abortion makes women’s claims for better working conditions lose a measure of legitimacy.

Throughout human history, children have been the consequence of natural sexual relations between men and women. Both sexes knew they were equally responsible for their children, and society had somehow to facilitate their upbringing. Even the advent of birth control did not fundamentally change this dynamic, for all forms of contraception are fallible.

Elective abortion changes everything. Abortion absolutely prevents the birth of a child. A woman’s choice for or against abortion breaks the causal link between conception and birth. It matters little what or who caused conception or whether the male insisted on having unprotected intercourse. It is she alone who finally decides whether the child comes into the world. She is the responsible one. For the first time in history, the father and the doctor and the health-insurance actuary can point a finger at her as the person who allowed an inconvenient human being to come into the world.

The deepest tragedy may be that there is no way out. By granting to the pregnant woman an unrestrained choice over who will be born, we make her alone to blame for how she exercises her power. Nothing can alter the solidarity-shattering impact of the abortion option.

Richard Stith teaches at Valparaiso University School of Law in Indiana.