The easiest way to measure the passage of time, of course, is to simply measure a pregnancy in weeks -- using Naegele's rule, this gives you a due date that is exactly 40 weeks from your last menstrual period. Measuring in weeks seems simple enough. We all can agree on what a week is, and there's so much that happens in a pregnancy that weeks are a convenient unit of time for describing these changes. Everyone knows that you're not really pregnant for the first few weeks before you've even ovulated, and everyone knows that baby's rarely come on their due dates, but according to this technically-unscientific-but-very-interesting website and graph, it's a good way of measuring for a reason.
So weeks are nice.
The trouble comes from the fact that, for whatever reason, most people don't like to describe pregnancies in weeks. I'm not really sure why this is, but most people seem to prefer months or trimesters. Months I can kind of understand -- it's a throwback to "how many periods have I missed?" kind of thinking. I'm not sure where trimesters came from, but I can also kind of see the appeal -- first you're "newly pregnant" and then you're "happily pregnant" and then you're "uncomfortably pregnant." It's nice, when you're in that "uncomfortably pregnant" stage to think of it as "the home stretch."
The three methods make oodles of sense on their own right up until the point where people try to start converting between these methods. All of a sudden, 40 weeks isn't divisible by three, so figuring out when you graduate to a new trimester becomes complicated. A month is not exactly 4 weeks, so calculating how many months pregnant you are becomes a headache.
It would be nice if someone would just do the math and make a blanket statement to everyone about what the official policy is, but for some reason nobody can agree. The end of the first trimester (to my knowledge) is never described as starting before 12 weeks, but it is alternatively listed as 12 weeks, 13 weeks, and 14 weeks (and various decimal or fractional amounts contained within these weeks, such as "12 weeks and such and such number of days"). The end of the second trimester is even more variably described, with authors listing anything between 25-28 weeks. By some calculators, I won't be in the third trimester for another week and a half and by others I have already been in the third trimester for a week and a half.
Calculating months is even more complicated. My last menstrual period was on June 9. Therefore, on December 9, I considered myself "6 months pregnant." By some people's calculators, I was at the 6 month mark over 2 weeks prior to this, because 24 weeks/~4 weeks per month = 6 months. However, of course we only actually have one month that is actually 28 days, and those other 2 or 3 days a month really add up. By the "a month is 4 weeks" logic, a pregnancy would last 10 months on average, and it really doesn't -- it's more like 9 months and a week extra.
Again, this is where I turn to the blog that I cited earlier, as the author has a mathematical formula for determining what she considers the appropriate milestone.
According to her formula, I am in my third trimester. (Yay! I don't have to wait another 3 days for the 27 week mark OR another 10 days for the 28 week mark -- I'm already there!). I am 6.1 months along, and have completed approximately 66.7% of my pregnancy.
To be honest, looking at the math involved, I have to say that I don't know why there is so much of a discrepancy between methods. This definitely seems the most logical to me.
It also seems to match up with what I have been feeling as I've entered the final trimester. I feel as though I've encountered some interesting shifts in the pregnancy within the last week or so. Not only has the hunger increased, but I've felt my belly getting larger, heavier and more noticeable. When I walk, I can see it swinging from side to side.
My midwife appointments have changed a bit too. At my appointment yesterday, the midwife palpated me more than usual and finally said, "I can't say for sure, but I'm pretty sure that this is a baby head." They hadn't tried to locate specific body parts before. She also found the heartbeat almost instantly and commented that the baby was running out of places to hide.
I also had my glucose screening yesterday. There had been some miscommunication about when we would be conducting the screening and so I was unprepared for the test (I had just eaten before my appointment). It made for a long evening (three hours for an appointment that I'd expected to take half an hour!), but I was glad that I waited around for my blood sugar to return to normal and then did the test that same evening. The blood draw wasn't as bad as I'd expected, and the result (a passing blood sugar level that was actually lower than the one that I had when they tested me at 6 weeks), was worth the extra wait time.
Overall, life is good. I'm in the home stretch!
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