Weights and Measures

by Jen on April 28, 2008

in Does this baby make me look fat?

Well, apparently I do have that much room in me for a baby. And measuring at 32 weeks means nothing.

The ultrasound went well, although I knew it wouldn’t be very exciting. When the PA had said to me on Wednesday, “At least you’ll get another look at the baby!” My thought was, “Well, not really…” I’d had an ultrasound at around 28 weeks with the Monkeyboy and I remembered how crowded he’d been then. I couldn’t even begin to imagine how cramped and pretzel-like this baby must be at 35 weeks.

Uh, pretty damn cramped and pretzel-like.

The ultrasound tech was very nice, one we’d had before. Although I could see the ultrasound screen they have angled for the parents to view, I couldn’t read the measurements at the bottom. I saw the Hubster shift in his seat so that he could read them, so I knew he’d tell me later. (I almost wish he hadn’t.)

After taking her time with all the usual measurements, including checking the amniotic fluid level, the tech spent a long time trying to get us a good 3-D (4-D?) ultrasound picture. I’ve always thought they were kind of creepy, but I guess when it’s your baby, it’s a little cooler. Kind of creepy-cool. But it still kind of looks like a generic baby, all smooshed up.
The baby kept his hand in front of his face almost the whole time (I’m sure due to the general smooshed-ness), but the tech was very persistent and even had me change positions a couple of times to try to get a good face shot. (I think she felt badly that we hadn’t been able to get a video last time because they didn’t tell us that they’d switched to DVD. I noticed that now in the waiting room, they have a sign that says you can buy a DVD or CD.)

After all if this, the tech left to make some calculations. When she returned, here’s what she laid on us: The amniotic fluid level looks fine. The baby looks just fine and based on the measurements they took, they can estimate the baby’s size at this time. The baby is not measuring small for dates like the PA worried.

Now, just for fun, let’s peruse a few selections of Your Pregnancy, Week by Week (Remember, I’m at 35 weeks):

Week 35 “Your baby now weighs over 5 1/2 pounds.” Uh, no. But that’s about what the Monkeyboy weighed at 34 weeks.
Week 36 “By this week, your baby weighs about 6 pounds.” Keep guessing.
Week 37 “Your baby weighs almost 6 1/2 pounds.” Getting warmer…
Week 38 “At this time, your baby weighs about 6 3/4 pounds.” Ding ding ding ding! We have a winner!

Right now they estimate the baby weighs about 6 pounds, 12 ounces. At 35 weeks 2 days. Now, I know that ultrasound estimates of the baby’s weight are notoriously inaccurate, but it’s hard not to get wrapped up in the numbers.

She said, “If you go to full term, we think the baby will weigh about 9 pounds, 1 ounce.”

Part of me is hardly shocked by this. When I was pregnant with the Monkey, I kept saying “If he goes to full term, I expect he’ll be at least an 8 pound baby.” My mother-in-law once asked me why I thought this, as the Hubster wasn’t that big at birth. “What did he weigh?” I asked her, although I knew the answer. “7 pounds, 15 ounces,” She answered. “You do realize that one more ounce would be eight pounds, right?” I asked.

Research about pre-term infants suggests that by their due date, they have caught up to what their birth weight should have been. By his due date, the Monkeyboy was 8 pounds 3 ounces. I myself had weighed 7 pounds, eleven ounces 35 years before when I was born (although I’m a short little thing now). Babies are just getting bigger these days, for a variety of reasons (like more nutritious foods and moms who don’t smoke through pregnancy or try to keep their weight gain to the recommended twelve pounds that was told to OldChristine’s mother back in 1970).

Now, I know that ultrasound estimates of fetal weight are notoriously inaccurate, with a margin for error reported, in the past, as being as high as 15-18%. However, they’re getting better. My research shows that while these estimates are somewhat unreliable when done after 37 weeks gestation (birth weights currently reported as within 11% of estimates), they’re considerably more reliable when done between 34 and 37 weeks (birth weights closer to within 6.2% or less of estimate). Much of the reason for ultrasounds being unable to reliably predict fetal weight after 37 weeks is that often by then, the baby’s head is engaged low enough in the pelvis that an accurate measurement can’t be made. So I guess there’s something to be said for the -2 station he’s been riding at, after all. The Hubster reported that when the ultrasound tech was determining the head circumference, the measurement came back as 37 weeks 4 days.

How is it that my fundal height suggests 32 weeks, but the ultrasound suggests a fetal weight of 37-38 weeks? I’m only 5’2″! Where the hell is this baby finding the room? Is my uterus a biological tardis, with more room on the interior than the exterior? Or is this an indication that in my case, the ultrasound is inaccurate and I’m just having an average baby?

Nobody is more aware of the truly ironic dichotomy presented by two of my biggest birth fears. First, that I would pPROM again and this baby would be born even earlier than the Monkeyboy. That obviously didn’t happen. Now I can replace that with the newfear, first foreshadowed by my 18-week level II ultrasound back in December, that this will be the Incred.ible H.ulk Baby.

When I raised this concern months ago with my OB (and reminded him that he commented on my small pelvis size during my first birth), he said we’d revisit the subject again if it became an issue. By the time I see him again on Wednesday, I’ll be 36 weeks and the baby, if the ultrasound is even reasonably close to accurate, will be about seven pounds (estimates usually add at least an ounce a day). I think the time has come to revisit this subject. (Fears: cephalo-pelvic disproportion, c-section due to macrosomia, shoulder dystocia, second-, third-, or fourth- degree episiotomy, among others).

I don’t know that there are any good answers to my questions or solutions to my concerns, but I’d like to start thinking up strategy. What I’d love is for this baby to decide to come on his own sometime within the next couple of weeks. I’d be open to discussing an induction after that point, after about 38 weeks, if my Bishop’s Score improves, but not before there’s some progress. My biggest fear is that I’ll just go to term with no plan, a possibly too big baby (for me) and the big sword of “what if” hanging over my head.

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