Gestational Math: 27 Weeks!

Today, I am 27 weeks pregnant!

Obviously, any given date in a pregnancy is essentially arbitrary. We don’t know the exact day of conception, we can’t know the exact day of unscheduled birth, and each embryo and fetus develops at its own rate. We identify the due date — more accurately but less popularly called the “guess date” by some — based on a 200-year-old formula called Naegele’s Rule; it actually calculates an estimated date with a standard deviation of 1-2 weeks, based on a 28-day cycle, and notwithstanding Leap Years. Consequently, one’s guess date is really just the center of the approximately month-wide window in which natural, on-time birth might occur. If I’m in line with most first-time American mothers, Kermie could make his appearance as early as April 16 or as late as May 4.

I bring this up because the majority of my pregnancy resources say that my third trimester begins a week from today — but my favorite iPhone app, as well as the pregnancy calculator provided by the Discovery Channel’s website, say that it begins today. I wanted to know the truth of the matter, so I’ve been investigating — and honestly, I’m still not 100% sure I know which one to believe.

“Trimester” has two different meanings, according to

definition of trimester

When I do the math, it seems to me that either definition leads to the same solution: the third trimester begins at week 27 (and the second trimester begins at about week 13.5). The confusion may come from the notion that a month is four weeks long — at which point, a normal human pregnancy would last 36 weeks, rather than 40. Realistically, though, most months are closer to 4.5 weeks long.

The Baby 2 See trimester calculator explains that trimesters can be divided up in three different ways, based on 1. actual fetal development (which seems the least arbitrary), 2. the idea that gestation will last 40 weeks (which imposes a man-made system on something natural), or on 3. the idea that it takes 38 weeks post-conception for the baby to fully develop (which has the flaws of the second system, plus the added uncertainty of knowing the precise date of conception).

System #3 figures that the third trimester begins halfway through the 27th week of pregnancy — assuming you know when that even is, since again it’s not generally possible to know exactly when conception took place.

System #2 figures that the third trimester begins on the sixth day of the 26th week of pregnancy.

And System #1 figures that, on average, the third trimester begins at Week 27.

So even though quite a few people and things out there will say otherwise, I think I feel comfortable in my claim that I have met the next big ole milestone in this journey.

happy third trimester with balloons

At 27 weeks gestation, Kermie weighs just about two pounds and is about 14.5 inches long. My app tells me that “Your baby is beginning a very active stage in its cramped quarters,” and it’s not kidding — I can feel Kermie moving around in there every day, at any time of day, but especially of an evening and as I’m lying in bed preparing to sleep. Many of the movements I feel seem smaller than before; this is partially an effect of his reduced space, and partially because there’s less amniotic fluid in there than there used to be, so I can feel things more.

He is learning to recognize his parents’ voices (and presumably, the sound of Paisley yelping at the television) but isn’t frightened of cymbal crashes a foot away from his little ears (or at least, I didn’t feel him react when my bass drumming and Kermie’s uncle’s cymballing got a little too close to one another). He can see, more or less, although he won’t be passing any vision tests any time soon. And he is strong enough, and occasionally energetic enough, to use the inside of my belly as a punching bag and make the entire thing rock up and down like a bounce-house.

The 26-week diagram prompted much hilarity; why, one wonders, did the artist feel the need to label the mother’s back? I mean, pregnancy has done a number on my intellect, but I’m still pretty confident that I can identify my back without any real difficulty. I am also uncertain that the average viewer-of-diagrams needed a reminder as to where the genitals of both child and mother were located. I rather prefer this week’s picture, which humanizes both parties and leaves the unnecessary labeling to other diagrams:

27 weeks pregnant

At this point in the game, things are getting pretty cramped in my innards. The uterus is almost all the way up to my ribcage, which means my lungs can’t expand to full capacity. From here on out, I may experience swelling, varicose veins, and what my app calls “sudden pressure on your bladder” — given that I felt like I had to go to the bathroom every ten minutes yesterday evening, I can just imagine.

Kermie was particularly annoying last night, although I’m not 100% sure he deserves all of the blame. My last class of the day gave me a headache, which didn’t improve much as the evening went on. By the time I went home, I just felt faintly cruddy in the way that sometimes indicates the onset of a cold. I had a hard time falling asleep, but probably nodded off a little after midnight. When I woke up at 2, thanks to my bladder and my annoying dog who forgets how to jump on the bed when it’s dark in the room, I had heartburn, ached all over, had crampy/twitchy feet and calves, itched, and had a complete set of very tight throat muscles that almost felt like a sore throat. On top of that, I was having one of those fits where you just can’t stand being touched, which resulted in me wriggling away from a very nice hug AND throwing my poor kitty off the bed/sofa multiple times. That kept me up for another hour or two, and I finally fell asleep on the couch in time to grab another hour of sleep before my alarm went off. By 5:15 AM, I no longer felt sick — but I felt (and feel) exhausted. Even Kermie was thrown off by my wacky night’s sleep; I can pretty much rely on the fact that he’ll be dormant first thing in the morning, but this morning he was wiggling around in there.

This has turned into a rather lengthy post, so I think I’ll wrap it up with a quick mention (for the record) of the weather. I suppose I shouldn’t complain; it’s got to be awfully rough to be “hugely gravid” in extreme heat. But our area is trapped in a cold wave that looks like it will never end, to the point where I’ve concluded that the Maya were correct and we’ve simply entered the next Ice Age. I am so thankful that I got a new coat last weekend — I knew I wasn’t warm enough, but I had no idea how cold I was until I wasn’t anymore! It’s hard to keep warm enough when your wardrobe is limited, and I’m afraid my warmest maternity pants and jackets aren’t liable to survive to a second pregnancy because I’m completely wearing them out. Lucky Kermie gets to wait out the Ice Age in his own personal hot tub….


2 thoughts on “Gestational Math: 27 Weeks!

  1. I can just say how wonderful. You know what? I did the math by months. Easy. And Andres was just 8 days short of my 9 months so there 🙂

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