I've seen OB's, CNM's, and CPM's for prenatal care. At the OB they refused to listen to me about my conception date and only wanted my LMP. With my longer cycles, this would have been quite inaccurate, but I knew that I wasn't staying with them so I didn't care. If I had been staying with them, I would absolutely have subtracted 14 days from my conception date to come up with a fake LMP that gave me my correct due date.
With the CNM's they wanted my LMP, but did listen to me when insisted that I knew my conception date. It took a bit of explaining and demanding, but then they actually asked me which due date I wanted and I obviously picked the later one. The 20 week u/s gave me a slightly earlier due date and they asked if I wanted to switch dates. I, of course, kept choosing the latest date.
With the CPM I worked with last time, she just asked for my due date. She also would have been completely fine with me going past 42 weeks as long as everything continued to look good.
So I think the answer to your question depends greatly on the type of provider you choose. I don't think it's ever a problem to make up an LMP (by subtracting 2 weeks) if you're certain of your ovulation day. If you have to go with an OB or midwife practice that you know will induce you or risk you out for going late then I would definitely consider fudging by a week and then make sure you receive careful monitoring if you make it to that extra week. Standing up for your right not to be induced is great, but they can drop you from their practice and that means you'd end up in the ER to deliver or having a UC. You might be fine with either of these options or you might not be.
Mama to Avalon 1/07 , Austin 1/10 in between and Avery 12/11
Just to clarify, I responded to the OP who (1) stated that she is planning on working with a home birth midwife during her next pregnancy and (2) did not mention longer-than-average cycles or even later-than-average ovulation, only that her first pregnancy went to 42 weeks (before being induced).
Giving an "LMP" date that is not technically true, but that is "accurate" within the 28-day-cycle model that most care providers employ (so, subtracting 14 days from your ovulation date, if you know it, or adding as many days as your cycle is over 28 days--for example, adding 6 days to your actual LMP if you have a 34 day cycle) is *not* the same, in my opinion, as giving an arbitrarily made-up LMP because your last pregnancy last longer than 40 weeks and you have a feeling it's going to happen again. In the first case, you are providing your care provider with the most accurate information (in terms of accurately dating the pregnancy), even if you have to give an untrue LMP to do it. (While I would like to think that an intelligent and reasonable care provider (OB, CNM, CPM or other) would listen and could comprehend that LMP does not always accurately determine a due date, I understand that that is not always the case.) In the second case, though, you are giving your care provider false information that will lead her/him to false conclusions, and may lead to less-than-optimal decisions being made about your care (transferring you to the hospital for a "preterm" birth that is actually not "preterm," for example). Most midwives I know are happy to let a pregnancy continue until its natural conclusion, assuming that everything is well, but knowing that a woman is 41, or 42, or 43 weeks when making decisions about how to care for her is pertinent, and a midwife should not be impaired by information you know to be false.
OP, I really think that if you explain your history to your midwife and explain your strong bias against induction, she will be reasonable--especially if you are *also* reasonable about perhaps being seen more frequently after, for example, 41 weeks. Or, for example, letting her listen for several minutes with the doppler (for reactivity and longer-term variability) after 41-42 weeks. (I don't know what her protocols are or what would be her comfortable--these are just a couple examples.)
Also, I would remind you that you have had ONE pregnancy. If you were to survey moms of 2, 3, 4, 5 or more, I bet you'd find a lot of women who had their babies at very different gestations from one pregnancy to the next. To be sure, some women tend to carry long than 40 weeks (I'm one!), but it is not a given that because your first baby came "later," your second will as well. We had a client whose first baby came prematurely at 33 weeks who was (understandably so!) very worried about preterm labor in her second. He was born at 42 weeks on the dot. I think her 3rd came within a couple days of its EDD. There's just no telling for sure when your baby will come.
Good luck--I'm hopeful and relatively confident that you can find a care provider reasonable enough to take your (accurate) information at make wise decisions with it.