Purpose: To estimate the effects of mode of delivery (MOD) on maternal and fetal outcomes after the estimated fetal weight (EFW) on third trimester ultrasound (US) is 4000g or 4500g.
Methods: Decision analytic models comparing cesarean delivery (CD) versus trial of labor (TOL) after a fetus is suspected to be either 4000g or 4500g by US during the third trimester in non-diabetic women. Ultimate MOD outcomes following TOL included spontaneous vaginal delivery, operative vaginal delivery, and CD. Baseline assumptions were derived from the literature, which included maternal death from 0.0002-0.0025% by MOD, shoulder dystocia from 0.65-17.7% by birth weight and MOD, and permanent brachial plexus injury 6.7%. Utilities were assigned, applied to life expectancy and quality-adjusted life years (QALYs) were generated for each outcome. Baseline and sensitivity analyses were conducted comparing outcomes and QALYs.
Results: With an US EFW of either 4000g or 4500g, TOL is the optimal mode of delivery when both maternal and neonatal QALYs are considered. TOL was associated with 0.06901 higher total QALYs compared to CD in the 4000g model, and 0.04659 higher in the 4500g model (table). In number needed to treat analyses for EFW 4000g, 1021 women must be delivered by cesarean to avoid 1 permanent brachial plexus palsy injury. This changed to 787 for the 4500g model. The table below presents number of outcomes per 100,000 deliveries. Table 1. Maternal and neonatal outcomes in the setting of macrosomia.
TOL for EFW >4000g | CD for EFW >4000g | TOL for EFW >4500g | CD for EFW >4500g | |
| CD | 40,448 | 100,000 | 45,944 | 100,000 |
| Shoulder dystocia | 3000 | 0 | 3300 | 0 |
| Permanent brachial plexus injury | 58.30 | 0 | 68.70 | 0 |
| Total QALYs | 56.50 | 56.43 | 56.48 | 56.43 |
Conclusion: TOL is the optimal mode of delivery for fetuses suspected to be either 4000g or 4500g in non-diabetic women. This analysis has important implications for decisions regarding choice of MOD in order to optimize lifetime maternal and neonatal outcomes.
Candidate for the Lee B. Lusted Student Prize Competition