Suspected big baby?

What would you do if an ultrasound shows that your baby is big? Many women have to answer that question for themselves. Their options are to plan a C-section, get induced before the baby gets any bigger, or do nothing and wait for labor to begin whenever their bodies and their babies are ready. Some women have extenuating circumstances that muddy the waters a bit, or cause them to have to make other decisions — for instance, some women are “risked out” of a planned home birth because of suspected big baby (macrosomia); others may not be allowed to have a VBAC (that is, if you can find a supportive hospital or doctor any more).

The first question I ask is, “How accurate is the fetal weight estimate, anyway?” Notoriously wrong, actually. Most estimated fetal weights are within 10% of the actual weight. That sounds pretty good. Unfortunately, that’s about a pound or a pound and a half off. This means that if your baby is estimated to weigh 7 &1/2 pounds, it could actually weigh anywhere from 6 to 9 pounds, according to this margin of error. And not all estimated fetal weights are within that 10% margin of error, either. Here is a wonderful link about suspected macrosomia, with a lot of birth stories about inaccurate estimated fetal weight. The stories include just about every variation you can think of — babies that were supposed to be normal weight, but — surprise! — they were actually “macrosomic” (but still completely normal); babies that were supposedly macrosomic, and the mothers had C-sections, or were induced, and — surprise! — they were actually normal weight, or even a bit on the small side. In Henci Goer’s book The Thinking Woman’s Guide to a Better Birth, she notes that when doctors think that a baby is big, they are more likely to intervene or call for a C-section (even when the baby’s actual birthweight is not “too big”), but when doctors think that a baby is not big, they don’t intervene, even when the baby’s actual birthweight is “macrosomic.”

Here are a few other links that I thought were interesting. This is a collection of links regarding various aspects surrounding macrosomia (inductions, C-sections, Apgar scores, shoulder dystocia, etc.). Here is an article discussing cephalopelvic disproportion (CPD), which is the typical reason given when women have C-sections for big babies. An article that appeared in the AAFP Journal concluded that pregnancies with suspected macrosomia should be handled “expectantly” and that interventions should only be used if labor does not progress as expected. It also includes a table with risk factors for macrosomia. This article by the National Institute of Health concludes “The best policy is to await spontaneous birth or to induce labor after 42 weeks completion.” And finally is a webpage that includes a lot of information about macrosomia, but I especially wanted to include it because of the “Big Baby Birth Stories” — most of these babies are in the 9 lb. range, but there are a few that were 11 lb. or more.

As far as personal experience goes, I’ve had one ultrasound, which was done late in my first pregnancy because the midwife thought she might have heard two heart-beats at the prenatal visit; the estimated fetal weight was 7 lb. 8 oz. When my baby was born 10 days later, his actual weight was 7 lb. 5 oz. (3 oz. less than the ultrasound estimate, at a time when babies gain about half a pound a week average). It was nearly 1 lb. off. One of my sisters-in-law had IUGR with her 2nd baby, so they kept close watch on her 3rd baby. A few days before she was born, they estimated her fetal weight as “lucky to be 6 pounds.” She was over 8 lb. (They had a hard time seeing anything of the baby because of the way she was positioned.)

My second son was 9 lb. 2 oz. My sisters’ sons (their 2nd babies) were both over 9 lb. (and we didn’t tear). Another sister-in-law’s first baby was 9 lb. 8 oz. (after pooping and peeing), and she didn’t tear at all, which is important to note because some people will say that “every woman tears when she gives birth to her first baby” and others will say that “all women tear if their babies are big.”