Lesson Learned #2

by Jen on May 14, 2008

in Does this baby make me look fat?,Lessons Learned

Just like a watched pot never boils, a watched cervix never dilates.

My 38 week appointment is later today, but I’m not holding out much hope that there’s been any progress since last week. I have been having cramping and lower back pain since Sunday, but I’m determined not to get my hopes up. What I’m focusing on instead is the unlikeliness that this really could be a nine pound baby. Instead, I’ve decided that it will be somewhere in the seven to eight pound range. (Yeah… like I really get to decide these things). A baby of that size makes sense to me, based mostly on my size (both pre-pregnancy and currently) and on Monkeyboy’s size. As the Hubster always likes to proclaim about our son, “50-75th percentile for height and weight, but 90th percentile in head circumference!” In his family, the boys just have big melon heads as kids. And it’s not the head that’s usually the problem when it comes to birthing a large baby (although it can be), it’s the shoulders.

Estimated weights for fetuses are based partly on ultrasound measurements of head circumference (also on abdominal circumference and femur length). But there are a range of other factors involved in assessing the chance of a large baby. According to this article, after gestational age (at 40 weeks, there’s a 12.3% chance of macrosomia) and maternal race (Caucasian babies tend to be larger), these “major parental, environmental, and pregnancy-specific determinants of birth weight” should be used to estimate the chance for macrosomia:

  • Maternal Height. “Family pedigree studies have shown that, on average, “big people have big babies and small people have small ones.” I’m 5’2.” Or, as I like to say: I’m not short; I’m built low to the ground for speed and accuracy.
  • Maternal Obesity. “…the more a mother weighs, the larger her fetus is likely to be.” I was a healthy weight and BMI before pregnancy.
  • Maternal Pregnancy Weight Gain. “…the greater the weight gain is, the larger the fetus is likely to be.” I’ve gained only 32 pounds so far… within the 25-35 pounds recommended weight gain. Hey, it’s not that I haven’t tried to gain more, what with my Oreo obsession and all.
  • Parity. “At term, a fetus typically gains 0.2-0.5 g/day for each increase of 1 in maternal parity.” So I can expect this baby to be a little bigger than the Monkeyboy. (But by this same reasoning, shouldn’t Michelle Duggar be giving birth to about a fifty-pound baby next New Year’s Day?)
  • Fetal Sex. “On average, male fetuses weigh more than females by 136 g (5 oz) at term.” Okay, so boys are bigger. What.ever.
  • Ambient Altitude. “…an increase in altitude of 1000 m accounts for a reduction in term birth weight of 102-145 g.” I knew we should’ve moved to Tibet for this pregnancy.
  • Maternal Hemoglobin Concentration. I’m not really sure what this is. There seems to be some connection between altitude and blood thickness. “The relationship between birth weight and circulating maternal hemoglobin concentration is inverse, such that for each 1.0-g/dL increase in maternal hemoglobin concentration, term birth weight is reduced by 89 g.” I know that because of my anemia, my hemoglobin is low. Does this mean anemia can cause bigger babies? Or is only the opposite true (that high hemoglobin causes smaller babies)?
  • Paternal Height. “Offspring of fathers with heights 2 SDs above or below the mean have a term birth weight that is increased or decreased by 125 g, respectively.” The Hubster is 6’4″, which is 76 inches. The mean height for an American male is 5’10″ (70 inches). The standard deviation is 3″ (actually, I think it’s 2.8″). So, the Hubster is at least two standard deviations above average height.
  • Cigarette Smoking. “A mother who smokes 1 pack per day will likely have a baby with a mean birth weight reduction of 240-360 g at term.” I don’t. Blech. Although, if I knew it would have helped in this situation, I might have listened to Troy McClure’s self-help tape “Smoke Yourself Thin.”
  • Glucose Tolerance. “Uncontrolled maternal diabetes mellitus is commonly associated with excessive fetal weight.” Not something I have to worry about, thankfully.

What I have going for me: Maternal height, maternal weight, and pregnancy weight gain. What I have working against me: Paternal height, male baby, gestational age > 37 weeks, Caucasian, and parity. Non-factors: Altitude, cigarette smoking, glucose tolerance, hemoglobin concentration (as far as I can tell).

What does all this mean? Who the hell knows. The same article has some information on working all of this into a complex equation to determine range of error in fetal birthweight prediction for a specific case. But as I always tell my students, I became a history teacher because it was my understanding there would be no math.

I know that I can handle birthing a seven to eight pound baby. Well, as much as I really know anything. This is all part of my think-positive, plan-of-no-plan. I’ll let you know how it all works out for me.

Leave a Comment

You can use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>

CommentLuv Enabled

Previous post:

Next post: