Churchill's parents' sex life: a footnote

In an article in the Daily Telegraph Andrew Roberts discusses a new book by Celia and John Lee called Winston and Jack: The Churchill Brothers. Roberts suggests that Lady Randolph Churchill is unlikely to have been pregnant at the time of her wedding, as between then and Winston Churchill’s birth there were only 230 days, i.e. just ‘one day short of the 33 weeks of normal pregnancy’. However, the period between conception and birth is usually calculated at 266 days / 38 weeks. This doubtless explains why the announcement in The Times ran: ‘On the 30th Nov, at Blenheim Palace, the Lady RANDOLPH CHURCHILL, prematurely, of a son.’ Of course none of this proves that Lord and Lady Randolph had sex before marriage (and what does it matter if they did?) but the question must remain open.