The legal limit is 24 weeks and in exceptional circumstances (usually that going full time will put the Mothers life at risk), it can be performed later.
Generally speaking, most women that just decide they don't want a baby for lifestyle or financial reasons will do it earlier.
Generally it is only if something shows up on the 20 weeks scan (which is actually called the Abnormality scan) indicating a serious problem with the baby's health that termination iis performed after that point. And as SoapLea says, it is not a pleasant experience physically, let alone the emotional side of it.
Denise's reaction to Libby's abortion, and the fact that she had both Chelsea and Libby when her circumstances were fair from ideal re the father's character and also, her being very young in Chelseas's case, I would imagine that she is Pro Life or at least, it isn't something she feels is right for her.