Helen M. Alvaré is a law professor at George Mason University and president of the Chiaroscuro Institute, a nonpartisan, nonprofit think tank that addresses issues of human sexuality, marriage and respect for life. It receives some funding from the the Chiaroscuro Foundation, of which Meg T. McDonnell is the communications director.

Pro-choice Americans must wonder from time to time what keeps pro-lifers going. Why don’t we lay down our signs, cease our marching and admit that we’ve been good and beaten for these 40 years since Roe v. Wade? One of us is a baby boomer, the other a millennial; our views may help others understand these things and, along the way, think about some rarely considered aspects of the U.S. experience with legal abortion.

The case for pro-life despair has more than a few compelling points. First, there is abortion itself — the destruction of a human life, at its most vulnerable stage, with the consent of the mother. In the United States, there are approximately 1.2 million abortions every year — more than 3,000 per day — according to the Guttmacher Institute. Second, there is the procedure’s legal status: Access to abortion is protected as a constitutional “right.”

This combination is often too much to bear, especially in light of a third consideration, the projected longevity and sheer legal weight of Roe and the cases that have followed it. It is incredibly hard to overthrow a Supreme Court precedent. And 40 years is a long time.

Next, there is the breadth of Roe. When the court announced that even last-trimester abortions for women’s health (described as including all factors relating to physical or emotional well-being or familial concerns) merited constitutional protection, states could no longer prohibit abortion at a particular time or for a particular reason. States do, of course, often regulate the conditions under which abortions go forward, but under current law they cannot effectively say no to any abortion at any stage.

Fifth, poor and minority women and girls get the short end of the stick. Even though they are the groups most supplied with free contraception by state and federal governments, they have the most non-marital pregnancies and abortions. Sadly, no one in either political party is talking about what we might offer poor and minority women — other than more contraception and abortion — to effectively break their cycle of non-marital pregnancies followed by abortions or single-parenthood.

Sixth, neither our National Institutes of Health nor any other major health-care body has seen fit to investigate how women in the United States fare after they have an abortion. All ideological disputes aside, this is an important question, given that abortion is one of the surgeries most frequently performed on women in America. High-quality European studies, including a September 2011 article in the British Journal of Psychiatry, suggest reasons to worry about what a U.S. investigation might show, including the likelihood of significantly increased risk of mental health problems and substance abuse.

Seventh, it is more than a little likely that legal abortion, alongside contraception, has changed the mating market for women by reducing the cost of sex and eliminating one of the incentives to wed. Among millennials, marriage is occurring later in life, if at all, and non-marital birth rates are climbing.

The eighth factor is related: Abortion seemed to suck all of the oxygen out of the room on the subject of women’s equality and freedom. Exhibit A: “Women’s Night” at the Democratic National Convention was obsessively focused on contraception and abortion. Why should we be surprised then that the United States has never seriously debated adopting any of those terrific European family-and-work policies that boomers were eagerly anticipating back in the ’80s, such as paid maternity leave with job security for the mother?

After this litany, what can explain the fact that the pro-life movement is “not dead yet”? For starters, science and technology have been very good to us over the past several decades. Embryology, genetics, neurology, not to mention ultrasound technology — they are probably responsible for the fact that none of the abortion-rights Web sites bothers any longer to attack the humanity of the unborn child.

Second, the human rights nature of the abortion debate just never gets old. Journalist Gail Collins can characterize abortion as a “privacy” matter 10 times per article, and it still fails to persuade. Pregnancy involves the mother’s body, but the child is not only hers. The unborn child is vulnerable and dependent. Evolving standards of decency compel us to treat the vulnerable with particular care.

Third, pro-lifers have persisted against opposition that can boast of significant amounts of money and academic credentials. Indeed, we are flourishing. Our ranks are most recently swelled by millennials who show up at the annual March for Life in cheerful droves, armed with clever signs and infectious enthusiasm.

You might think that eight to three are bad odds — eight reasons to be overwhelmed, three reasons to fight another day. But when one of the three reasons is “because we’re fighting for human rights,” odds don’t matter. The cause still stirs the blood of a boomer and a millennial alike.