Depending on your scientific perspective, it can be argued that eggs and sperm are alive. At a minimum, sperm are alive. They are created, they move, and after a time, particularly when exposed to certain external factors, they die and their bodies decay.
Eggs contain all of the tissue that becomes the zygote, other than a tiny strand of DNA. The difference in size between an egg and a sperm is roughly the Empire State Building relative to a pencil eraser. The eggs are created while the woman is still a fetus in her mother's womb. They definitely decay over time to a point where they are no longer able to be successfully inseminated and grow into a healthy fetus. Whether they can be said to have "life" or not is up for debate.
If a sperm is alive, then surely the zygote is alive. It may be tiny and consisting of only a few cells but it takes in energy and will continue to divide and grow into a human if nothing else happens to it. 1/3 of fetuses do not survive pregnancy due to miscarriage. It's a very fragile little life, and just because the insemination worked does not mean that it will be able to develop into a healthy baby.
Let's risk everyone's ire and consider babies. Based on many understandings of mammal procreation and development, human babies are still fetuses. Women's pelvises are not large enough to pass a fetus at the point of maturity of most mammals, so basically we give birth early and they are still a fetus for another 9 months or so.
So, if sperm are alive, should we condemn every act that results in sperm death? Should men not be allowed to ejaculate except when attempting to procreate? Should they not be allowed to wear tight clothing or go into hot tubs? Should they be fined for nocturnal emissions while they are asleep? No. That's ridiculous.
So, we see that there is a continuum of life starting with sperm, and somewhere along the development from sperm to 9-month old child, we have to decide at what age it is no longer acceptable to deliberately end that life, and under which circumstances. I agree with the standard that once a fetus is able to survive outside the mother's body with normal nourishment and care but no extra machines or devices, deliberately ending that fetus' life should not be allowed. Whether you want to call it a baby or a fetus is basically irrelevant, as I have shown. It is alive, has been alive since well before anyone would have insisted it could not be killed, and will continue to live as long as it's given the same normal care of any other infant.
The precise line we should draw until that point is a bit more murky. It isn't fair to penalize a woman without access to a fabulous neonatal unit if her premature fetus doesn't survive. It isn't fair to hold the neonatal staff legally responsible if they are not able to save every premature birth. They are already working against nature, and every baby they save should be considered a miracle of modern medicine.
Part of the problem is that different human fetuses survive outside the womb at different lengths of gestation. At some point in the third trimester, most fetuses can be born early and still be okay. Birth up to two weeks early seems to have almost as positive an outcome on average as on the due date.
Should we set the abortion limit at two weeks prior to due date? That's an uncomfortable choice. Already by that point, if the mother isn't having noticeable health problems, little will stop the pregnancy from successfully producing an infant.
If the mother IS experiencing health problems, she should have options. Her life is sacred, too. At some point most neonatal units could keep a fetus alive if it were delivered by induced vaginal birth or C-section. I don't know what that age would be, possibly a month early.
Electing an abortion for financial or emotional concerns at this point really shouldn't be allowed. You already had 4-8 months to figure those out. You and your fetus have already survived most of the pregnancy with your health intact, so if at that point you really don't want the baby or believe you can't take care of it, you can hang on a little longer and give it up for adoption. We'll help you survive through the end of it, but it isn't right to kill it when it's this close to a successful birth and life.
First term abortions performed by experienced medical professionals are very safe. They are safer than pregnancy.
Pregnancy is not always according to the will of the mother (or father). Rape and incest are real, as is the failure of contraception. Unquestionably, first term abortions should be legal. You can argue in favor of restrictions or requirements. This post is about "life" and in terms of life and health, when abortion should be made illegal.
I am not a medical professional, but I think it could be successfully argued that for many women, it would be appropriate and safer for them to choose to have an abortion into the second trimester, perhaps up to the 4th or 5th month. Maybe it should have stronger restrictions on it, but there's no strong reason why a woman should be prevented from having an abortion up to the 4th month. There's no way that fetus is going to survive into a healthy child no matter how many miracles you perform. Some women don't even realize they are pregnant right away, so there needs to be a little leeway.
So, I propose that abortion be freely allowed up to the 4th month, allowed with restrictions up to the 5 1/2 month (or somewhat later depending on the consensus of the medical knowledge), but from that point should only be allowed to protect the health of the mother. Seriously, if you couldn't figure out you were pregnant and that you really didn't want to have a baby right now up until that point, despite being physically able to, you have bigger problems and should talk to a gynecologist and/or a therapist.