The process of conception is very chancy, with a randomly timed act of intercourse having a significantly less than one in ten probability of conception and with the conception probability peaking at around 1/2 for an act occurring at around ovulation. Any couple who knows these facts, absent some further information (such as a private revelation from God) cannot rationally expect a pregnancy to result from a sexual act, nor can the couple rationally be said to plan the pregnancy in a sexual act, for it is presumptuous to have something so chancy be one's plan. Thus, if a couple is rational and knows the probabilities, a pregnancy's resulting from a particular sexual act will always be an unexpected and non-planned consequence, though perhaps a hoped for and intended one.
However, the probability of conception for regular sexual activity over a longer period of time, say a year, is higher, and better than even. If something has a better than even probability, then it can be expected. Nonetheless, unless that probability is pretty high, say 9/10, which over the period of a year it is not, then it still is presumptuous to talk of the outcome as planned.
Thus, pregnancy is too chancy an event for it to be rationally planned, though of course it always can be planned for—even very low probability events can be rationally planned for. The standard loose distinction between planned/unplanned pregnancies, and to a lesser degree that between expected/unexpected pregnancies, can be replaced by a distinction between pregnancies hoped for and not hoped for, intended and not intended. (Note that "unhoped for" is not the same as "not hoped for". We use "unhoped for" in the case of events that are evaluated by the subject in a positive way, but a pregnancy need not so be. Likewise, Ryan Wasserman has argued that "not intended" is not the same as "unintended".) Of course, it may be that this is what people have all along meant by the words "planned", "unplanned", "expected" and "unexpected", but in a conceptually confused way. But in a matter as important as this, conceptual clarity is needed.