More radically, you can also go in the opposite direction. Infants have no memories for the first year or two. They see upside-down at first. Brain development is clearly continuing after birth. So you might be able to justify infanticide for some time after birth. I don't recommend this, of course.
There's no sense in assigning value to life as a step function, where one nanosecond before it it's categorically not human and therefore disposable, yet one nanosecond afterwards it's a human and therefore killing it is immoral.
It may make practical sense to define laws that pretend that it's a step function, but it makes no moral reasoning sense.
I lean more towards the "early fetus is valuable" side of things, since I view future human life that hasn't been experienced yet as valuable. This is, after all, the main reason we care about rather nebulous existential risks - it'd be a shame if future humans never got the chance to exist. We therefore recognize that future human life has some value. Also, I'm well aware of the reductio ad absurdum that can be levied against my position, but I believe that that runs both ways.
Another point in support of this (rather horrific and terrifying) view is how babies were treated 200 years ago. Names were not given at birth, important religious events were postponed, etc. Until the parents had some reason to believe the baby will survive more than a year (which was not all that certain), they were not bestowing much humanity on the kid.
