Of course they should.
Actually, i'd personally have had a child with eg Edwards (and some, a very few, have survived a while) but would have chosen a none medicalised home birth so the child could die there if intended.
Other disorders I would have to think about; if I were otherwise childless probably more liekly to deliver at term that putting my other children through it.
I suppose what I think is that women aren't always informerd either about the vast range of emotions they may experience (from absolute relief through to utter despiar) or the relaities of life with different outcomes of pregnancy, such as a chidl with SN ornindeed having a child when mum has health issues.
I woudl stand up and campaigne for that to happen, and probaly do in my way, and have in the past been told that wishing women to have more of an experience of for example DS to draw on when making decisions is ultiamtely me being anti abortion; I disagree. I am anti uninformed abortion, which really is the same as being pro choice: pro informed, supported choice.
A women's right to choose is absolute within the contraints of the law (I do think the 0alw allows terminations for too long when tehre are no health risks including psychiatric trauma to mother but don't campaign on that and we are allowed our own personal opinions); but choose emans accessing rinformation that can be hard to come by. A few eyars ago I refused an amniocentesis for ds3: we'd ahd a highish risk bloods result. Instead of accepting that I was posted a leaflet called your baby has downs syndrome which in my pregnant state just seemed a list of fatal complications, even though probably it was not.
That's not free choice. Real choice is about having grown up alongside disabled kids (even if not at school with you- some obv. need snu provision as does ds3 and ds1 if he gets his aplce); knowing the relaities from the absolute love to the sheer tiredness of decades of sleep deprivation.
And it simply isn't inforrmation easy to get out there: threads here in the past reflect that- the pregnanct woman who thanked someone on SN for allowing ehr to relaise that in fact m,ums of disabled kids did love their children as mcuh as anyone else; threads where giving information about actual risks to mothers making post- prenatal dx decisions is considered as being anti termination (had Mum already decided it would be wrong unless there was clear evidence that it was based on a false belief such as all DS babaies having terminal heart conditions); in my own life my sister who despite watching two of my children being dx'd with ASD (almost amusingly after scares for DS ds3 now has a compeltely different dx!) and still thinks that a set of clear tests gusranatees a SN free baby so a few terminations and the world would be totally NT.... it's all very fiddly.
But to sum it up: I support informed termination but don't beleive full information is easily available to all women in cases such as SN yet.