Photo Credit: Mongkol Akarasirithada

The following is a summary of “Fetal growth restriction and small for gestational age as predictors of neonatal morbidity: which growth nomogram to use?,” published in the December 2023 issue of Obstetrics and Gynecology by Leon-Martinez, et al.

Fetal growth nomograms are crucial in identifying fetal growth restriction and guiding clinical management to enhance perinatal outcomes. Nevertheless, the literature needs consensus on the gold standard among these nomograms. For a study, researchers sought to compare the predictive capabilities of four commonly used nomograms (Hadlock, International Fetal and Newborn Growth Consortium for the 21st Century, Eunice Kennedy Shriver National Institute of Child Health and Human Development–unified standard, and World Health Organization fetal growth charts), along with one institution-specific reference, in anticipating small for gestational age (SGA) and adverse neonatal outcomes.

A retrospective cohort study encompassed all nonanomalous singleton pregnancies that underwent ultrasound at ≥20 weeks of gestation between 2013 and 2020 at a single academic center. Employing random selection methods, the study sample was limited to one pregnancy per patient and one ultrasound per pregnancy, conducted at ≥22 weeks of gestation. Fetal biometry data were utilized to calculate estimated fetal weight and percentiles based on the five mentioned nomograms. Maternal and neonatal data were retrieved from electronic medical records. Logistic regression was applied to assess the association between estimated fetal weight percentiles and the risk of SGA and neonatal composite outcomes, including various adverse events. Receiver operating characteristic curve contrast estimation and test characteristics were computed for all nomograms to evaluate their predictive performance for SGA and neonatal composite outcomes. Additionally, analyses were conducted using ultrasounds performed within 28 days of delivery to assess prediction accuracy.

Among the 10,045 participants, the percentage of fetuses classified as <10th percentile varied from 4.9% to 9.7% across nomograms. Fetuses with an estimated fetal weight <10th percentile had an elevated risk of small for gestational age (odds ratio, ranging from 9.9 [95% CI: 8.5–11.5] to 12.8 [95% CI: 10.9–15.0]) and the neonatal composite outcome (odds ratio, ranging from 2.4 [95% CI: 2.0–2.8] to 8.8 [95% CI: 6.6–11.8] for <10th percentile and 5.7 [95% CI: 4.5–7.2] to 8.8 [95% CI: 6.6–11.8] for <3rd percentile). The prediction of small for gestational age with an estimated fetal weight <10th percentile yielded positive likelihood ratios of 6.3 to 8.5 and an area under the curve of 0.62 to 0.67. Similarly, predicting the neonatal composite outcome with an estimated fetal weight <10th percentile resulted in positive likelihood ratios of 2.1 to 3.1 and an area under the curve of 0.55 to 0.57. When analyses were restricted to ultrasounds within 4 weeks of delivery, the risk of small for gestational age increased across all nomograms (odds ratio, ranging from 16.7 [95% CI: 12.6–22.3] to 25.1 [95% CI: 17.0–37.0]), with improved prediction (positive likelihood ratio, 8.3–15.0; area under the curve, 0.69–0.75). Similarly, the risk of the neonatal composite outcome increased (odds ratio, ranging from 3.2 [95% CI: 2.4–4.2] to 5.2 [95% CI: 3.8–7.2]), with marginal improvement in prediction (positive likelihood ratio, 2.4–4.1; area under the curve, 0.60–0.62). Importantly, the risk of both small for gestational age and the neonatal composite outcome further increased (odds ratio, ranging from 21.4 [95% CI: 13.6–33.6] to 28.7 [95% CI: 18.6–44.3]), with greatly improved prediction (positive likelihood ratio, 6.0–10.0; area under the curve, 0.80–0.83).

The extensive cohort study demonstrated that Hadlock, recent fetal growth nomograms, and a locally derived fetal growth reference perform comparably in predicting small for gestational age and neonatal composite outcomes.

Reference: ajog.org/article/S0002-9378(23)00433-7/fulltext