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Clinical Obstetrics

Poster Session 1

(279) Advanced Maternal Age and Risk of Pathologic Fetal Growth

Tuesday, February 13, 2024
10:30 AM – 12:00 PM  
Location: Prince George's Exhibit Hall CDE, Lower Atrium Level
Objective:

Advanced maternal age is associated with an increased risk of underlying comorbid disease and pregnancy complications, which are associated with both small (SGA) and large (LGA) for gestational age birth weight. For this reason, some centers perform serial growth surveillance in all AMA women, but the independent affect of age on birth weight is unclear. The objective of this study was to analyze a large population of AMA women and assess risk of SGA and LGA accounting for known confounders.

Study Design:

This was a population based retrospective study of all singleton, non-anomalous, genetically normal gestations ≥ 20 weeks gestational age in a national registry of live birth vital statistics data from 2020-2022. Women were stratified by age categories in five-year increments from 15-49 years old. The primary outcome was risk of large (LGA, birth weight >90%) and small (SGA, birth weight < 10%) for gestational age birth weight assigned by sex-specific Fenton criteria. Poisson regression with robust error variance was performed to generate adjusted risk ratios (aRR) among age categories using ages 25-29 years old as the referent adjusting for chronic hypertension, hypertensive disorders of pregnancy, pregestational and gestational diabetes.

Results:

A total of 7,022,461 pregnancies were included in this analysis with 9.4% and 9.1% classifying as LGA and SGA, respectively. In unadjusted analysis, rates of SGA decreased and rates of LGA increased with advancing maternal age; Figure 1. The risk of LGA was elevated for all age categories above age 25 and highest among ages 35-39 (aRR 1.20, CI 1.19-1.21). Conversely, the risk of SGA was highest for ages less than 25, and highest among age 15-19 (aRR 1.57, CI 1.55-1.58) and age 20-24 (aRR 1.23, CI 1.23-1.24).

Conclusion:

Advancing maternal age is associated with decreasing rates of SGA and increasing rates of LGA birth weight that was independent of known comorbid conditions and pregnancy complications.