Curriculum · Gynecology / Women's Health / Infertility / Perinatal Care / Birth Spacing
Fetal macrosomia
What it is
Fetal macrosomia is the large baby, described in the neonate as large for gestational age with a birth weight above the 90th percentile. An EFW of 4 kg at 37 weeks with normal liquor and a normal placenta is the picture, and even when the OGTT and every other test in the pregnancy have been normal, GDM and macrosomia of unknown cause both stay on the list.
Causes and risk
Diabetes is behind most of it. Macrosomia is one of the fetal complications of GDM, and previous macrosomia at 4.5 kg is itself a reason to screen for GDM early. Weight also counts against a trial of vaginal birth after Cesarean: an EFW above 4 kg in DM, and above 4.5 kg in a woman without it, is listed among the factors that increase the failure rate. Shoulder dystocia, the event macrosomia leads to, has its own risk factors: previous shoulder dystocia, DM with a large baby, obesity, and induction of labour.
How it is diagnosed
A fundal height above what the dates would give raises it: at 28 weeks a fundal height of 33 cm has macrosomia and polyhydramnios as its two differentials. EFW on the scan then settles the size.