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.

Zusammenfassung

Ziel Ziel dieser Studie war es, den Einfluss von Messungenauigkeiten der fetalen Gewichtsschätzung bei Makrosomie auf den Entbindungsmodus und neonatale Outcomeparameter (NO) zu untersuchen.

Methoden Bei 14 633 Schwangerschaften zwischen 2002 und 2016 untersuchte diese retrospektive Studie den Zusammenhang zwischen der sonografischen fetalen Gewichtsschätzung, dem tatsächlichen Geburtsgewicht (BW), dem Entbindungsmodus (primärer Kaiserschnitt (pCS), sekundärer Kaiserschnitt, vaginale Entbindung und operative vaginale Entbindung) und den NO-Parametern (5-Minuten-Apgar < 7, pH-Wert < 7,1, Aufnahme auf der neonatalen Intensivstation (NICU), Schulterdystokie). Eingeschlossen wurden Einlingsschwangerschaften > 37 + 0 Wochen mit sonografisch geschätztem Fetalgewicht (EFW) innerhalb von 7 Tagen vor Entbindung. Die Studienpopulation wurde in 4 Gruppen unterteilt: Gruppe 1 (falsch negativ): EFW < 4000 g/BW ≥ 4000 g; Gruppe 2 (richtig positiv): EFW ≥ 4000 g/BW ≥ 4000 g; Gruppe 3 (falsch positiv): EFW ≥ 4000 g/BW < 4000 g; Gruppe 4 (richtig negativ): EFW < 4000 g/BW < 4000 g.

Ergebnisse Erwartungsgemäß wurde die höchste Rate an sekundären Kaiserschnitten (sCS) in Gruppe 2 (richtig positiv) gefunden (30,62 %), verglichen mit nur 17,68 % in Gruppe 4 (richtig negativ). Die sCS-Rate in der falsch positiven Gruppe 3 war signifikant höher (28,48 %) im Vergleich zur falsch negativen Gruppe 1 (21,22 %; OR 1,48; 95 %-KI 1,16–1,89; p = 0,002). Im Vergleich mit der richtig negativen Gruppe 4 zeigten univariate Analysen signifikant höhere sCS-Raten in allen anderen Gruppen: Odds Ratio (OR) 2,06 für Gruppe 2 (95 %-KI 1,74–2,42; p < 0,001), 1,85 für Gruppe 3 (95 %-KI 1,54–2,22; p < 0,001) und 1,25 für Gruppe 1 (95 %-KI 1,05–1,49; p < 0,01). Es wurden keine signifikanten Unterschiede zwischen den Gruppen 1 und 3 für die NO-Parameter 5-Minuten-Apgar < 7 (p = 0,75), pH < 7,1 (p = 0,28) oder NICU-Aufnahme (p = 0,54) gefunden. In Gruppe 1 bestand jedoch eine signifikant höhere Wahrscheinlichkeit für Schulterdystokie als in Gruppe 3 (OR 4,58; 95 %-KI 1,34–24,30; p = 0,008).

Schlussfolgerung Sonografische Messungenauigkeiten des EFW bei fetaler Makrosomie scheinen einen größeren Einfluss auf den Entbindungsmodus zu haben als das Geburtsgewicht selbst. Eine Unterschätzung des fetalen Gewichts kann mit einer höheren Wahrscheinlichkeit für Schulterdystokie assoziiert sein.

Key words

cesarean section rate - fetal weight estimation - fetal macrosomia - perinatal outcome - sonography

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