Impact of Using Abdominal Circumference Independently in the Diagnosis of Fetal Growth Restriction

Neonatal Outcomes among Fetuses with an Abdominal Circumference <3rd %ile and Estimated Fetal Weight 3rd to 9th %ile Compared to Fetuses with an EFW <3rd %ile

OBJECTIVE

Fetal growth restriction (FGR) is defined as an estimated fetal weight (EFW) or abdominal circumference (AC) <10th percentile (%ile) for gestational age (GA). An EFW <3rd %ile for GA is considered severe FGR (sFGR). It remains unknown if fetuses with isolated AC <3rd %ile should be considered sFGR. Our primary objective was to assess composite neonatal outcomes in fetuses with an AC <3rd %ile and overall EFW 3rd to 9th %ile compared with those with an EFW <3rd %ile.

STUDY DESIGN

This retrospective cohort study was undertaken at a tertiary academic center from January 2016 to December 2021. Inclusion criteria were singleton fetuses with an EFW <3rd %ile (Group 1) or AC <3rd %ile with EFW 3rd to 9th %ile (Group 2) at 28 weeks' gestation or greater. Exclusion criteria were multiple gestations, presence of a major fetal anomaly, resolution of FGR, genetic syndrome, or infection. Composite neonatal outcome was defined by any of the following: neonatal intensive care unit admission >48 hours, necrotizing enterocolitis, sepsis, respiratory distress syndrome, mechanical ventilation, retinopathy of prematurity, seizures, intraventricular hemorrhage, stillbirth, or death before discharge. Small for gestational age (SGA) was defined as birth weight <10th %ile for GA.

RESULTS

A total of 743 patients fulfilled our study criteria, with 489 in Group 1 and 254 in Group 2. The composite neonatal outcome occurred in 281 (57.5%) neonates in Group 1 and 53 (20.9%) in Group 2 (p < 0.01). The rates of SGA at birth were 94.9 and 75.6% for Group 1 and Group 2, respectively (OR 5.99, 95% confidence interval 3.65-9.82).

CONCLUSION

Although AC <3rd %ile with EFW 3rd to 9th %ile is associated with a lower frequency of SGA and neonatal morbidity than EFW <3 %ile, fetuses with AC <3 %ile still exhibited moderate rates of these adverse perinatal outcomes. Consideration should be given to inclusion of an AC <3rd %ile with EFW 3rd to 9th %ile as a criterion for sFGR. However, prospective studies comparing delivery at 37 versus 38 to 39 weeks' gestation are needed to ensure improved outcomes before widespread adaptation in clinical practice.

KEY POINTS

· The composite neonatal outcome occurred in 57.5% of fetuses with an overall EFW <3rd %ile and 20.9% of fetuses with an AC <3rd %ile but EFW 3rd to 9th %ile.. · Both groups demonstrated a high positive predictive value for SGA birth weight.. · Consideration should be given to inclusion of an AC <3rd %ile as a criterion for sFGR..

Is there an association between isolated sonographic abdominal circumference below the 10th percentile and placental vascular lesions?

OBJECTIVE

To study the association between prenatal diagnosis of isolated abdominal circumference (AC) below the 10th percentile (AC <10th) in appropriate for gestational age (AGA) neonates and placental vascular lesions.

METHODS

A prospective study was conducted of healthy women who underwent sonographic fetal biometric measurements, up to 7 days before delivery, and delivered AGA neonates. The study cohort was divided into those with and without prenatal isolated AC <10th. Placental histopathology lesions were classified into maternal and fetal vascular malperfusion (MVM, FVM) lesions.

RESULTS

Compared to the AC over 10th percentile group (n = 85), the AC <10th group (n = 85) was characterized by lower maternal body mass index, higher rate of smokers, and increased rate of induced labor (P = 0.029, P = 0.029, P = 0.001, respectively). There were no between-group differences regarding maternal age, gestational age, and neonatal outcome. Mean placental weight was lower in the isolated AC <10th (P < 0.001). The rate of MVM or FVM lesions did not differ between the groups. By multivariate logistic regression analysis, isolated AC <10th was not found to be associated with increased risk for placental vascular lesions.

CONCLUSION

Isolated AC <10th is associated with increased rate of induction of labor; however, it is not associated with increased placental vascular lesions.