The following is a summary of “Risk of adverse perinatal outcomes in pregnancies with “small” fetuses not meeting Delphi consensus criteria for fetal growth restriction,” published in the October 2023 issue of Obstetrics and Gynecology by Powel, et al.

Previous investigations into the association between clinical characteristics, sonographic indices, and the risk of adverse perinatal outcomes in pregnancies complicated by fetal growth restriction have faced challenges due to the absence of a universally agreed-upon definition. In 2016, an international panel of experts established a consensus definition through the Delphi procedure, but the definition had yet to be universally endorsed by professional organizations. For a study, researchers sought to determine whether an independent association exists between estimated fetal weight and/or abdominal circumference below the 10th percentile and adverse perinatal outcomes when growth restriction criteria are not met according to consensus standards.

Data were extracted from a passive prospective cohort of singleton nonanomalous pregnancies at a single academic tertiary care institution spanning 2010–2022. The cohort comprised three groups: consecutive fetuses meeting the Delphi criteria for fetal growth restriction, small-for-gestational-age fetuses not meeting consensus criteria, and fetuses with birthweights between the 20th and 80th percentiles randomly selected as an appropriately grown comparator group. This nested case-control study employed 1:1 propensity score matching to adjust for confounders among the three groups. The primary outcome was a composite of perinatal demise, 5-minute Apgar score <7, cord pH ≤7.10, or base excess ≥12. Pregnancy characteristics with a P value <0.2 in univariate analyses were considered for inclusion in a multivariable model alongside fetal growth restriction and small for gestational age to identify predictive factors for adverse perinatal outcomes independently.

In total, 2,866 pregnancies met the inclusion criteria, and after propensity score matching, 2186 matched pairs were formed. These pairs consisted of 511 (23%) small-for-gestational-age, 1,093 (50%) appropriate-for-gestational-age, and 582 (27%) fetal growth restriction patients. Adverse perinatal outcomes were observed in 210 pregnancies (10%). Notably, none of the pregnancies with small-for-gestational-age or appropriate-for-gestational-age fetuses resulted in perinatal demise. Among the small-for-gestational-age group, 23 of 511 patients (5%) experienced adverse outcomes, while 77 of 1,093 patients (7%) in the appropriate-for-gestational-age group had adverse outcomes (odds ratio, 0.62; 95% CI, 0.39–1.00). Furthermore, 110 of 582 patients (19%) with fetal growth restriction meeting consensus criteria had adverse outcomes (odds ratio, 3.08; 95% CI, 2.25–4.20), including 34 patients with perinatal demise or death before discharge. Factors independently associated with increased odds of adverse outcomes included chronic hypertension, hypertensive disorders of pregnancy, and early-onset fetal growth restriction. Small-for-gestational-age was not associated with the primary outcome after adjustment for six other predictive factors. The bias-corrected bootstrapped area under the receiver operating characteristic curve for the model predicting adverse perinatal outcomes was 0.72 (95% CI, 0.66–0.74). Additionally, the bias-corrected bootstrapped area under the receiver operating characteristic curve for a 7-factor model predicting adverse perinatal outcomes was 0.72 (95% CI, 0.66–0.74).

The study concluded that fetuses with an estimated fetal weight and/or abdominal circumference ranging from the 3rd to the 9th percentile but not meeting the consensus criteria for fetal growth restriction do not exhibit an increased risk of adverse outcomes. The absence of evidence supporting elevated risk suggested that most of these cases represent constitutionally small yet healthy fetuses. While close monitoring was recommended to exclude evolving growth restriction, subjecting these fetuses to the same management as those with suspected pathologic growth restriction may lead to unnecessary antenatal testing. Additionally, it could heighten the risk of iatrogenic complications associated with the premature or early-term delivery of small fetuses that are, in reality, at a relatively low risk of adverse perinatal outcomes.

Source: ajog.org/article/S0002-9378(23)00275-2/fulltext