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Macrosomia

  • Practice Bulletin PB
  • Number 216
  • January 2020

ABSTRACT: Suspected macrosomia is encountered commonly in obstetric practice. As birth weight increases, the likelihood of labor abnormalities, shoulder dystocia, birth trauma, and permanent injury to the newborn increases. The purpose of this document is to quantify those risks, address the accuracy and limitations of methods for estimating fetal weight, and suggest clinical management for a pregnancy with suspected macrosomia. This document has been revised to include recent literature and updated information on the prevention of macrosomia.

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Reaffirmed 2023

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Figures & Tables

Figure 1. Increased risk of adverse outcomes by macrosomia category. Open bars, Category 1 (4,000–4,499 g); gray bars, category 2 (4,500–4,999 g); black bars, category 3 (5,000+ g). The reference group is 3,000–3,999 g. All bars more than an odds ratio of 1 are significant at P <.05. Abbreviations: Asst Vent > 30, assisted ventilation more than 30 minutes; CPD, cephalopelvic disproportions; IMR, infant mortality rate. (Modified from Boulet SL, Alexander GR, Salihu HM, Pass M. Macrosomic births in the United States: determinants, outcomes, and proposed grades of risk. Am J Obstet Gynecol 2003;188:1372–8.)

Figure 1. Increased risk of adverse outcomes by macrosomia category. Open bars, Category 1 (4,000–4,499 g); gray bars, category 2 (4,500–4,999 g); black bars, category 3 (5,000+ g). The reference group is 3,000–3,999 g. All bars more than an odds ratio of 1 are significant at P <.05. Abbreviations: Asst Vent > 30, assisted ventilation more than 30 minutes; CPD, cephalopelvic disproportions; IMR, infant mortality rate. (Modified from Boulet SL, Alexander GR, Salihu HM, Pass M. Macrosomic births in the United States: determinants, outcomes, and proposed grades of risk. Am J Obstet Gynecol 2003;188:1372–8.)

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Figure 2. Frequency of shoulder dystocia for increasing birth weight by maternal diabetes status and method of vaginal delivery—spontaneous or assisted. (Reprinted from Nesbitt TS, Gilbert WM, Herrchen B. Shoulder dystocia and associated risk factors with macrosomic infants born in California. Am J Obstet Gynecol 1998;179: 476–80.)

Figure 2. Frequency of shoulder dystocia for increasing birth weight by maternal diabetes status and method of vaginal delivery—spontaneous or assisted. (Reprinted from Nesbitt TS, Gilbert WM, Herrchen B. Shoulder dystocia and associated risk factors with macrosomic infants born in California. Am J Obstet Gynecol 1998;179: 476–80.)

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Table 1. Birth Weight Percentiles for Gestational Age: U.S. 2011 Single Live Births to Resident Women Between 37 Completed Weeks of Pregnancy and 42 Completed Weeks of Pregnancy (Based on Best Obstetric Estimate of Gestational Age)

Table 1. Birth Weight Percentiles for Gestational Age: U.S. 2011 Single Live Births to Resident Women Between 37 Completed Weeks of Pregnancy and 42 Completed Weeks of Pregnancy (Based on Best Obstetric Estimate of Gestational Age)

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