Jerseybeachmama - I think having little ones puts an extra strain in the marriage. Some couples just can't cope very well with the stress. H doesn't cope well with any stress, for that matter, and I pretty much fell apart in the first year of S1's life.
Sometimes I wonder if one of the reasons H detached is because of this pregnancy, since he knows when a newborn is here, we could start that stressful interaction all over again.