The Good News:
The Court upheld the part of S. 243 which says that it is wrong to conceal the death of a child who died before birth.
The goal of protecting unborn children is reaffirmed:
"By facilitating the investigation of the offences discussed above, s. 243 ultimately serves to protect children born alive and a subset of children that died before birth. " 
The Court upholds the idea that at least some fetuses are unborn children. Which bears repeating in the context of the abortion debate.
The Bad News:
The Supreme Court raised the bar in terms of which fetuses are covered under this section.
The Court referred to the Berriman case, which involved this section. The judge in the Berriman case said that S. 243 only applied to fetuses who might have been born alive.
The Supreme Court says that it applies to fetuses who were likely to have been born alive.
That lessens the coverage of this provision, because whereas a third trimester would have likely been born alive, a late second trimester might have been born alive.
So that's something of a loss for the pro-life movement.
The ruling also said that a fetus becomes a child at viability. Personally, I'd never seen the Supreme Court define when a fetus becomes a child. This could also be very bad news. Section 243 applies to miscarried children, not miscarried fetuses.
I think overall this ruling was a slight loss for the unborn, with some silver lining on the push for protecting of late-term fetuses.
I think there is material there to help build a legal case for defense of at least late-term unborn children.
The notion that late-term fetuses are children but not human beings is clearly discriminatory to me.