OB Guideline 23: Macrosomia

For the purposes of these Guidelines, fetal macrosomia implies growth beyond 4,500 grams (approximately 1 percent of live born infants achieve this birth weight). Risks for morbidity for birthing person and baby increase significantly beyond this weight compared to the general population. Clinical palpation and sonography are similar in their ability to estimate the presence of macrosomia.

Prenatal Counseling

When macrosomia is clinically suspected, patients should be informed of the potential risks and such discussion should be documented in the prenatal record.

Birthing person risks include:

increased likelihood of cesarean delivery,
vaginal lacerations, and
postpartum hemorrhage.

Fetal risks include:

shoulder dystocia,
fractured clavicle, and
injury to the nerves of the brachial plexus producing symptoms ranging from temporary upper extremity weakness to permanent paralysis. Most infants delivered vaginally with birth weight >4,000 grams and a brachial plexus nerve injury do not have a permanent paralysis.

Intrapartum Counseling

The responsible intrapartum clinician should confirm that the patient understands the risks and document this in the intrapartum record.

Delivery Options

If the estimated fetal weight is 5,000 grams or greater (4,500 grams or greater for infants of diabetic birthing people), then prophylactic cesarean delivery may be considered.

Induction of labor for macrosomia before 39 0/7 weeks is not recommended because it does not improve outcomes. Current evidence is unclear as to whether induction of labor for macrosomia after 39 weeks prevents shoulder dystocia.

Footnotes