Influence of Estimated Fetal Weight on Labor Management
01 March 2019
09 July 2019
20 August 2019 (online)
Objective Prior studies suggest knowledge of estimated fetal weight (EFW), particularly by ultrasound (US), increases the risk for cesarean delivery. These same studies suggest that concern for macrosomia potentially alters labor management leading to increased rates of cesarean delivery. We aimed to assess if shortened labor management, as a result of suspected macrosomia (≥4,000 g), leads to an increased rate of cesarean delivery.
Study Design This is a secondary analysis of a retrospective cohort study at a single tertiary center in 2015 of women with singleton pregnancies ≥36 weeks with documented EFW by US within 3 weeks or physical exam on admission. Women were excluded if an initial cervical exam was ≥6 cm or no attempt was made to labor. In addition, patients were excluded for the diagnosis of hypertension, diabetes, or prior cesarean delivery, as these comorbidities influence the use of US, labor management, and cesarean delivery independent of fetal weight. Patients were classified as EFW of ≥4,000 and <4,000 g. Secondary analysis examined the impact of US within 3 weeks of admission when compared with physical exam at the time of admission. The primary maternal outcomes were duration of labor and cesarean delivery. Duration of labor was evaluated as total time from 4 cm to delivery (with 4-cm dilation being a surrogate marker for active labor), length of time allowed from 4 cm until the first documented cervical change (or delivery), and time in second stage of labor (complete dilation to delivery). Cesarean delivery for arrest of labor was a secondary outcome. Student's t-test, Mann–Whitney U-test, chi-squared test, and Fisher's exact test were used for univariate data analysis as appropriate.
Results Of 1,506 patients included, 54 (3.5%) had EFW of ≥4,000 g. Women with EFW of ≥4,000 g had a larger body mass index, higher fetal birth weight, were more likely to be undergoing induction of labor, had a more advanced gestational age, and were more likely to have had an US within 3 weeks of delivery. They were more likely to undergo cesarean delivery (29.6 vs. 9.3%, adjusted odds ratio [AOR]: 2.7, 95% confidence interval [CI]: 1.3–5.5) despite not having shortened labor times. When analyzing this population by method of obtaining EFW, those with EFW based on US rather than external palpation were more likely to undergo cesarean delivery (13.1 vs. 7.9%, AOR: 1.5, 95% CI: 1.01–2.12), again without having shortened labor times.
Conclusion EFW of ≥4,000 g and use of US to estimate fetal weight do not appear to shorten labor management despite being associated with an increased risk of cesarean delivery.
- 1 Kjaergaard H, Olsen J, Ottesen B, Nyberg P, Dykes AK. Obstetric risk indicators for labour dystocia in nulliparous women: a multi-centre cohort study. BMC Pregnancy Childbirth 2008; 8: 45
- 2 Caughey AB, Cahill AG, Guise JM, Rouse DJ. ; American College of Obstetricians and Gynecologists (College); Society for Maternal-Fetal Medicine. Safe prevention of the primary cesarean delivery. Am J Obstet Gynecol 2014; 210 (03) 179-193
- 3 Little SE, Edlow AG, Thomas AM, Smith NA. Estimated fetal weight by ultrasound: a modifiable risk factor for cesarean delivery?. Am J Obstet Gynecol 2012; 207 (04) 309.e1-309.e6
- 4 Scifres CM, Feghali M, Dumont T. , et al. Large-for-gestational-age ultrasound diagnosis and risk for cesarean delivery in women with gestational diabetes mellitus. Obstet Gynecol 2015; 126 (05) 978-986
- 5 Rouse DJ, Owen J, Hauth JC. Criteria for failed labor induction: prospective evaluation of a standardized protocol. Obstet Gynecol 2000; 96 (5 Pt 1): 671-677
- 6 Friedman EA. Evolution of graphic analysis of labor. Am J Obstet Gynecol 1978; 132 (07) 824-827
- 7 American College of Obstetricians and Gynecologists; Society for Maternal-Fetal Medicine. Obstetric care consensus no. 1: safe prevention of the primary cesarean delivery. Obstet Gynecol 2014; 123 (03) 693-711
- 8 Zhang J, Troendle JF, Yancey MK. Reassessing the labor curve in nulliparous women. Am J Obstet Gynecol 2002; 187 (04) 824-828
- 9 Zhang J, Landy HJ, Branch DW. , et al; Consortium on Safe Labor. Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol 2010; 116 (06) 1281-1287
- 10 Gifford DS, Morton SC, Fiske M, Keesey J, Keeler E, Kahn KL. Lack of progress in labor as a reason for cesarean. Obstet Gynecol 2000; 95 (04) 589-595
- 11 Cheng YW, Hopkins LM, Laros Jr RK, Caughey AB. Duration of the second stage of labor in multiparous women: maternal and neonatal outcomes. Am J Obstet Gynecol 2007; 196 (06) 585.e1-585.e6
- 12 Stephansson O, Sandström A, Petersson G, Wikström AK, Cnattingius S. Prolonged second stage of labour, maternal infectious disease, urinary retention and other complications in the early postpartum period. BJOG 2016; 123 (04) 608-616
- 13 Allen VM, Baskett TF, O'Connell CM, McKeen D, Allen AC. Maternal and perinatal outcomes with increasing duration of the second stage of labor. Obstet Gynecol 2009; 113 (06) 1248-1258
- 14 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 (05) 1372-1378