Influence of Sonographic Fetal Weight Estimation Inaccuracies in Macrosomia on Perinatal Outcome.

ABSTRACT

OBJECTIVE: To evaluate the influence of inaccurate sonographic fetal weight estimation in macrosomia on the mode of delivery and neonatal outcome (NO). METHODS: In 14 633 pregnancies between 2002 and 2016, this retrospective study evaluated the association between sonographic fetal weight estimation, true birth weight (BW), mode of delivery (primary cesarean section [pCS], secondary cesarean section, vaginal delivery, and operative vaginal delivery rates) and NO parameters (5-min Apgar < 7, pH < 7.1, neonatal intensive care unit [NICU] admission, shoulder dystocia). Singleton pregnancies > 37 + 0 weeks with ultrasound-estimated fetal weight (EFW) within 7 days before delivery were included. The study population was divided into four groups Group 1 (false-negative) EFW < 4000 g/BW ≥ 4000 g; Group 2 (true-positive) EFW ≥ 4000 g/BW ≥ 4000 g; Group 3 (false-positive) EFW ≥ 4000 g/BW < 4000 g; and Group 4 (true-negative) EFW < 4000 g/BW < 4000 g. RESULTS: As expected, the highest secondary cesarean section (sCS) rate was found in Group 2 (true-positive) (30.62 %), compared with only 17.68 % in Group 4 (true-negative). The sCS rate in the false-positive Group 3 was significantly higher (28.48 %) in comparison with the false-negative Group 1 (21.22 %; OR 1.48; 95 % CI, 1.16 to 1.89; P = 0.002). In comparison with the true-negative Group 4, univariate analyses showed significantly higher rates for sCS in all other groups odds ratio (OR) 2.06 for Group 2 (95 % CI, 1.74 to 2.42; P < 0.001), 1.85 for Group 3 (95 % CI, 1.54 to 2.22, P < 0.001), and 1.25 for Group 1 (95 % CI, 1.05 to 1.49; P < 0.01). No significant differences were found for NO between Groups 1 and 3 for the parameters 5-min Apgar < 7 (P = 0.75), pH < 7.1 (P = 0.28), or NICU admission (P = 0.54). However, there was a significantly higher chance for shoulder dystocia in Group 1 compared with Group 3 (OR 4.58; 95 % CI, 1.34 to 24.30; P = 0.008). CONCLUSION: Sonographic EFW inaccuracies in fetal macrosomia appear to have a greater impact on the mode of delivery than birth weight itself. Underestimation of fetal weight may be associated with a higher probability of shoulder dystocia.