Cameron's views on abortion have a certain logic if you are pro-abortion (pro-choice). that is if you accept the empirical assumption that easier abortion at an early stage leads to less late abortions – the flaw in this reasoning is that you assume a fixed number of abortions, irrespective of abortion laws,whereas evidence from the US is that more liberal abortion leads to more abortion overall.
The logic of personal identity as conceived today also supports the avoidance of late abortions since an early foetus can be seen as less human than a more developed one. It is interesting that this conception of personal identity shows the similar philosophical underpinnings of progressive liberalism and old-style soviet communism; there was no sense of a unified personality continuing over time, a person being merely the totality of his behaviours and therefore infinitely mutable. this conception is needed for pro-abortion too; as I understand it the western legal system depends on the continuity of the person over time.
Cameron is also for abortion of disabled children up to birth; he cited his own experience of bringing up a severely disabled child. This argument has some plausibility until you consider how under the same provisons of the act, children are aborted for cleft palates and webbed feet – 40 in 200? according tothecatholicherald.