The basic view on abortion is "No", unless it is necessary to save the life of the mother, in which case the intention would be different to simply aborting the fetus. The Buddhist view is that when conception occurs, there is a living being at the moment of conception. Terminating it at any time is considered killing.
Australia has a beneficial way of getting around the difficulties that some women have who cannot keep their child due to various reasons. It is called "open adoption." For open adoption, the woman goes through the pregnancy and the child is adopted by somebody whom the mother chooses. The mother is able to visit the child, about five or seven times in a year, so that the mother is able to share in her child's life as they grow up.
If you know somebody who becomes pregnant and doesn't really want the child, there are alternate ways, at least in Australia, maybe also here in Singapore. I don't know, but there are usually places to go where perhaps an adoption can be arranged and even open adoption where the woman is able to be part in the raising up of the child.
We have seen that when we've had interviews with women who had abortions, there's often a lot of self-hatred, a lot of guilt, a lot of regret. It doesn't help the women at all in the long run to have had an abortion. People often think short term, "I don't want it now", but in the long term, by having an abortion, they're causing themselves a lot of pain.
We know one woman who got a lot of blame for choosing open adoption rather than abortion because the family had different views on this subject. Naturally the woman is happy she was strong enough to resist that blame and be part of her child's life.
As to teenage pregnancy, same thing, allow it to happen, but the teenager may need a lot of support. If the teenage girl or her mother doesn't want to take the child, they can allow it to be adopted by someone who does want the child. There are a lot of people in the world who would like to have kids but who don't have them. So putting children up for adoption is not a hard thing, at least not in the West. I can't speak for Singapore, but just to be aware of the Buddha's views on it, the moment of conception is the creation of a living being.