Characteristics and pregnancy outcomes of undetected fetal macrosomia
Keywords:
Birth weight, Cesarean section, Fetal macrosomia, Shoulder dystociaAbstract
Objective: To identify antenatal characteristics associated with undetected macrosomia, as well as predictors for adverse maternal and neonatal outcomes.
Methods: Medical records of women who gave birth to term macrosomic infants at Tuen Mun Hospital between 1 January 2019 and 31 December 2023 were retrospectively reviewed. Comparisons were made between women with antenatally detected macrosomia by ultrasound (estimated fetal weight ≥4000 g) within 1 week before delivery and women with antenatally undetected macrosomia. Logistic regression analysis was performed to determine independent predictors for Caesarean delivery, composite adverse maternal outcomes, and composite adverse neonatal outcomes.
Results: Of the 360 macrosomic cases during the 5-year study period, 265 (73.6%) were undetected antenatally and 95 (26.4%) were detected antenatally. Compared with the undetected group, the detected group had a higher pre-pregnancy body mass index (24.8 vs 23.2 kg/m2, p=0.024), a higher rate of elevated pre-pregnancy body mass index (48.4% vs 33.2%, p=0.008), a higher rate of shoulder dystocia in a previous pregnancy (3.2% vs 0%, p=0.018), a higher rate of polyhydramnios (11.6% vs 2.3%, p=0.001), a higher rate of pregnancy-related problems (45.3% vs 29.8%, p=0.006), and a greater number of ultrasound scans (2 vs 1, p<0.001). All cases of perineal traumas, shoulder dystocia, and birth injuries occurred in the undetected group. Antenatally detected macrosomia was independently associated with Caesarean delivery (adjusted odds ratio [aOR]=89.26, p<0.001), increased composite adverse maternal outcomes (aOR=2.73, p<0.001), and decreased composite adverse neonatal outcomes (aOR=0.32, p=0.001).
Conclusion: Antenatal detection of macrosomia decreases neonatal complications but increases maternal complications and Caesarean delivery rates. Counselling regarding macrosomia should involve a shared decision-making process based on evidence-based recommendations.
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