Should you keep the child, and should anyone force you to, legally or ethically? And why?
I will go from the cold facts to the feelings that hit home, and will try to expend the most of my knowledge without boring people.
The brass tacks
Before getting to all the statistics and the ethics, lets first agree that pregnancy is a natural thing, a necessary thing, and not one bit unique in the animal kingdom. The rat, the monkey, the horse, the sheep and yes, mankind, keep their lineage going by keeping getting pregnant and procreate.
Yet human pregnancy is a little bit more special (I'm still staying with the facts here). See, mankind is unlike most of the animal kingdom when it comes to sex. With the exception of the bonobos, the homo sapiens is the only species that uses sex more than simply procreation and a seasonal enjoyment. Sex is a symbol. Sex is a connection. And, oh yes, sex is pleasure. So while animals have sex to have offsprings, we human have sex to achieve a lot more things.
Like a burger at first...
So why do we have sex?
Well, let me digress a bit. Through evolution, nature gives us certain rewards for completing certain things. For example, in the wild, there is always a paucity of energy. Eating gives us pleasure, because nature rewards us for storing up some strength and keeping alive. It is almost universal knowledge that fatty and sweet food gives the most energy per mass compare to other types of food (starchy food are rare, so we don't have a craving for such things). And it is, ahhah, natural, that we get the most reward from nature with a fatty and sweet culinary experience. Corporations like McDonald's and Burger King spend millions to find the sweet spot for their simple-looking recipe, to get people to crave and crave.
...but actually so, so much more
So for actions that increases that chance of survival for you as an individual and your species as a whole, the brain rewards you with an awesome thing called dopamine. Dopamine makes it feel good to find a shelter. Dopamine makes that greasy burger extra tasty, and make foie gras and Beluga caviar the most covetted culinary experiences despite their ethics. Dopamine is the bounty shot for when we get new things - since new things means more ways to survive. Explains why you get hyped for Pokemon X for months and then settle down after playing it for half a week, no? Dopamine is why you love having friends (that awesome BFF feeling is about nature telling you that having a BFF is good for combat and foraging, not because of spa day), why you like achieving things, and more.
And for the ultimate survival action - breeding, dopamine gives us a shot of pleasure so large magazines and tabloids worldwide spend 90% of the pages to tell people how to get it. There's even a name for it. Orgasm.
and it leads us back to our thing
All in all - having a child is sometimes undesirable. It's easy to say that when you don't actually have a child coming.
But let's say you (or your loved one), like millions with unplanned pregnancy, actually are pregnant.
There comes our issue.
Let's all agree that we will keep the fetus if we can.
And if we really are in a pickle, now we'll talk. Again with the facts.
Conciousness, or in more flowery artsy words, the soul, defines a human.
Cogito ergo sum. I think, therefore I am - said René Descartes.
The thinking mind, the breathing soul is what makes a human truly human - you can lose a limb, hell, you can lose all your limb, but as long as you are screaming and cursing whatever fate that brough you to this limb-less situation, you are a human, and with it comes all your rights.
It is, naturally, a question to ponder as to when the fetus is accounted as a full, right-bearing human?
A human fetus has a minimal brain stem (like that of a worm) at 7 weeks old. At the third trimester of the pregnancy, the fetus will develop some conciousness but in a dream state, and only at birth will the baby be truly concious. As such, while fetal nerve cells can receive some trauma (like most cellular structure), pain receptors are not there until the thrid trimester. As the British House of Lords decreed in 2000 on Fetal Sentience after a scientific jury, higher-brain function develops at about the 23rd week into pregnancy.
So while an almost-born human fetus (about 1 or 2 months before labour) should be considered a full human, at least in legal rights, full-human wise, for a considerable length of time in the early prenatal stages the fetus is not a human, in the most philosophical sense of the term.
So is it wrong to abort a fetus (while it is not yet a full human)
I would not abort my child, even if it is a tiny batch of cells, fully knowing that.
But some people might think differently, and it is fine by me. What is not fine is people trying to force their ideas on other people. Some people will never abort a child. Some people won't even use contraception. Others will do it like rabbit and abort just as frequent. Their choices.
Since it doesn't matter scientifically, then it should be up to whoever wants to do whatever
The fetus cannot feel pain, or feel most things, in its early stages. In the weeks before the 7th it can't even feel or fire neurons systematically - making it even less than a bit of your arm. So as long as it is under those time constraints, scientifically it should be acceptable.
Having a choice doesn't mean people will be aborting more (pro-choice activists are usually advocates for sexual education and freedom, which in fact reduce the mischance of abortion), nor does banning abortion outright will stop it in its entirety. In El Salvador, abortion is a crime worth 30 years in jail yet abortion pills are abound in the black market, without medical supervision.
Why I think pro-choice is a more ethical point of view
Pro-choice is pro-freedom, and pro-equality.
Choice means you can keep the fetus. Choice means you can keep your life, should you choose to. Choice means you can live with your belief, and you can live without one. Just because you don't like how someone else eats a cake in their house doesn't mean you have the right to flip it to the ground, or worse, lobby the government so that police will fo the cake-flipping for you.
Choice is pro-equality, because even after the advent of contraception like condoms and hormonal tablets, in a relationship we as men can just dusts off his shirt and walk away. Choice means that women can also take control of their lives, that they too can stand up from a mistake, or a horrible mishap (rape, incest, prostituion) in their lives - that they can dusts of their shirts and walk away as well.
I doubt that someone who cures cancer can come out of an unwanted pregnancy
There certainly are stories of successful people out of unwanted pregnancy - I'm saying unwanted, because if it is unplanned, the mother and father not wishing to abandon their child would at least have been wanted. However, those stories are few and far in between, because it is almost an universal truth that someone unwanted would have had a much worse childhood and upbringing than one that is needed and loved.
Would a child of an inexperienced teenager, who herself is not ready, be in a better footing than others? Or a rape victim, be it incest, statutory or just plain, painful rape? One out of a one-night stand, of a playful and uncaring mother? From the red-light district? There can be so many more.
Say about try-hard attitudes all you want but we cannot deny how our path is shaped from the moment we were conceived. For every CEO from an orphanage there are 9 from a trained, intellectually advanced family.
So while it is not impossible, it is numerically challenged enough to be highly improbable.
There are many other child issues that should be rectified instead of this obviously freedom-of-choice option. Like LGBTQ adobting kids, for example. Theirs are adoptions out of choice - and the kid is chosen, not a haphazard mishap like that of an unwanted pregnancy.
These are my thoughts.