Association of Doppler parameters with placental signs of underperfusion in late-onset small-for-gestational-age pregnancies.

Objective: To elucidate the association between Doppler parameters and histological signs of placental underperfusion in late-onset small-for-gestational-age (SGA) babies.

Methods: Umbilical, fetal middle cerebral and uterine artery pulsatility indices and umbilical vein blood flow (UVBF), which had been recorded within 7 days prior to delivery, were analyzed from a cohort of SGA singleton pregnancies delivered after 34 weeks' gestation and confirmed as having a birth weight < 10(th) percentile by local standards. In each case, the placenta was histologically evaluated for signs of placental underperfusion using a hierarchical and standardized classification system. The independent association of the Doppler parameters with placental underperfusion was evaluated using logistic regression and decision tree analysis.

Results: In 51 cases (53.7%), there were 61 placental histological findings indicative of placental underperfusion. These cases had a significantly higher incidence of Cesarean section for non-reassuring fetal status (52.1% vs 11.9%; P < 0.001) and neonatal metabolic acidosis at birth (21.6% vs 0%; P = 0.001). Significant and independent contributions to the presence of placental underperfusion lesions were provided by increased mean UtA pulsatility index (PI) (P = 0.018; odds ratio (OR) 2 (95% CI, 1.1-3.7)) and decreased UVBF normalized to estimated fetal weight (P = 0.027; OR 0.97 (95% CI, 0.95-0.99)). The combination of both parameters revealed three groups with differing risks for placental underperfusion: normalized UVBF > 82 mL/min/kg (risk 31.3%), normalized UVBF ≤ 82 mL/min/kg and mean UtA-PI ≤ 95(th) percentile (risk 65.5%), and normalized UVBF ≤ 82 mL/min/kg and UtA-PI > 95(th) percentile (risk 94.4%).

Conclusions: In late-onset SGA pregnancies, uterine Doppler and UVBF are surrogates for placental underperfusion. These findings facilitate phenotypic profiling of cases of fetal growth restriction among the general population of late-onset SGA babies.