The impact of composite maternal & fetal ultrasound assessment on the mode of delivery in large-for-gestational-age fetuses: the macrodia trial.

OBJECTIVE

To evaluate maternal and fetal determinants of unplanned operative delivery in large-for-gestational-age fetuses.

DESIGN

Prospective, non-randomized, multicenter study.

SETTING

Hospital-based.

POPULATION: Singleton pregnancy, not affected by gestational diabetes, with an ultrasound diagnosis of large fetuses, but not within the ACOG criteria for macrosomia.

METHODS

Per protocol, early induction of labor was scheduled when estimated fetal weight (EFW) and/or abdominal circumference (AC) >95th or when EFW and/or AC between 80th and 95th with unfavorable maternal indices, height < 155 cm and/or subpubic angle (SPA) < 100°. Expectant management was planned in cases without these maternal unfavorable indices.

MAIN OUTCOME MEASURES: Unplanned operative delivery (vacuum-assisted or cesarean section). The proportion of unplanned operative delivery was compared between groups managed per protocol. The proportion of unplanned operative delivery of recruited women who were managed in violation of protocol was also analyzed and compared with that of those managed per protocol. The EFW to subpubic angle ratio (EFW/SPA) and the head circumference to subpubic angle ratios (HC/SPA) were evaluated by ROC analysis, and adjusted relative risks (RRs) for unplanned operative delivery were estimated using Poisson regression on the entire study population.

RESULTS

Of the 223 patients included, 127 were managed per protocol (102 early induction, 25 expectant), while 96 were managed at clinicians discretion. Unplanned operative deliveries were more frequent among women induced per protocol than among those managed expectantly (52.9% vs. 12.0%; p < 0.01). We also found that women who should have been induced per protocol, but underwent expectant management had a similar higher proportion of unplanned operative deliveries (59.6%). In multivariable analysis, EFW/SPA ratio ≥34.78 (RR = 1.71) and HC/SPA ratio ≥3.30 (RR = 1.39) - the optimal ROC-derived cutoffs - were associated with a higher risk of unplanned operative delivery.

CONCLUSIONS

Unplanned operative delivery was associated with unfavorable fetal biometry/maternal-subpubic-angle ratios, which may help identify women at higher risk, providing a promising additional support for individualized delivery management.