I recommend, from time to time, trying on an opposing viewpoint, like trying on new fashions in a changing room. Approaching problems from a different point of view—even intractable problems, from a diametrically-opposed point of view—can produce gainful insights. You may even change your mind. But even if you don't, I find it's a good thought exercise; subjecting your convictions to philosophical "stress tests" is a good way to fortify them against future attack.
It's in this spirit that I approach the subject of abortion from a pro-life perspective—the opposite of my own pro-choice convictions. However, most arguments against abortion are religiously-informed and, in my opinion, unconvincing; there would be no novelty in simply repeating these, and I don't propose to do that. Rather, I intend to make as persuasive a secular case against abortion as I can (and then refute it.)
But I must first dispense with the notion that men—or transgender women, in my case—are not entitled to an opinion on abortion, because it's a solely an issue of women's agency. Abortion is a complex issue—an intersection of science, religion, philosophy, and law. If you take the pro-life view that abortion is "murder," and that a million unborn persons are "murdered" each year in the United States, it's inconceivable that you wouldn't have a strong "anti-murder" stance. (In fact, it perplexes me that pro-life legions aren't protesting in the streets every day, if they sincerely believe that mass murder is being perpetrated on a routine basis.) The idea that men should be excluded from having a view on the subject is nonsense.
With that said, most of the abortion debate is about "when life begins," but this is a nebulous, unhelpful phrase. A zygote—that is, the cell that is formed when a female reproductive cell and a male reproductive cell join—is "alive," and it contains human DNA. It is, therefore, a living human thing, just as a hair follicle is a living human thing. What matters is not "when life begins"—plants are alive too, after all—but when a human thing becomes a human being. In other words, a legal person with human rights.
We now find ourselves in the realm of philosophy, and what it means "to be."
(But before I go on, allow me to dispose of one proposed criteria for personhood that has found traction in recent years—that of the heartbeat. Numerous state laws have been enacted that ban abortion after a fetal heartbeat is detected, usually around 6 to 7 weeks of pregnancy. This criteria is based on nothing but rank sentimentality. Animals have beating hearts, but we slaughter and eat them. Moreover, a human body in a vegetative state, with a fully-functioning heart but with no higher brain function, does not a meaningful life make. Opponents of abortion will need to do better than this.)
To make a complex philosophical issue simpler than it is, let's agree that to have the experience of being implies some degree of awareness of one's surroundings and oneself. The cerebral cortex—the structure of our brain that differentiates us from mere animals, and is responsible for perception, awareness, thought, memory, and consciousness—doesn't develop until 20 to 24 weeks. This is also when a fetus can (probably) feel pain, and is considered "viable." Abortions after this point are considered "late-term," and are seldom done for elective reasons.
Let's assume then that the pro-choice position I'm arguing against is that there's no compelling case for the personhood of a fetus before 20 to 24 weeks.
That may be so, but surely a fetus is still a category of person—a "potential person"—and "potential persons" do have certain rights. Consider, for instance, a newborn child. She isn't considered a full, legal person until the age of majority, usually 18 years of age. But despite being not-quite-a-person, she does have an undisputed right to life. This is because we expect her to develop into a functioning adult person eventually. Why should we expect anything different of her as a fetus? A child's rights are held "in trust," as it were, until she develops into a full-grown, responsible adult, but a fetus has no such rights. Why? Isn't birth an arbitrary point at which to confer rights? Why not prior to birth? We confer value onto a fetus, after all—we form emotional bonds with it, we give it a name, and we grieve at miscarriages.
To refute this argument, I would point out that a fetus, before 20 to 24 weeks, and a newborn child simply aren't comparable, despite whatever value we may confer upon it. A child is an autonomous person, aware of herself and her surroundings, and possessing a distinct personality. In other words, a fully-formed human being, with an interest in survival. A fetus has none of these characteristics. It is a blank canvas, not a painting. (At best, it is a work in progress.) Abortion does no harm because there is no human being who is harmed.
You may call this "the tyranny of the Existing," but the fact remains that "potential" existence does not have the same value as currently existing, any more than a seed is considered a tree. We may speak abstractly about our obligations to future generations, but it's not apparent at all that we owe any favors to the not-yet-existing. We have only those obligations to future generations that we ourselves decide we do (even then, we don't always fulfill those obligations—see climate change, for instance.)
But I suppose, at the end of the day, if I could make a convincing pro-life argument, I would be pro-life. This was the best that I could do. Maybe my hypothetical questions are thought-provoking, maybe not. But they aren't persuasive, to me at least. Perhaps I'm merely at the limits of my imagination, and you have a more compelling non-religious case against abortion? If so, I would be interested to read it in the comments. Although I'm unlikely to agree, I can only benefit from having my views challenged, and I commend all of us to do it more often.