Performance of common fetal growth standards in pregnancies affected by systemic lupus erythematosus.

OBJECTIVE

The aim of this study was to compare the performance of different fetal growth reference standards-Hadlock, INTERGROWTH-21st, and World Health Organization-in pregnancies complicated by systemic lupus erythematosus.

METHODS

This retrospective cohort study was conducted at a tertiary referral center and included singleton pregnancies delivered at ≥22 weeks of gestation. Pregnant women were classified into two groups: those with systemic lupus erythematosus, defined by ≥4 American College of Rheumatology criteria, and controls without autoimmune disease. Estimated fetal weight obtained from routine obstetric ultrasonography was converted into gestational age-specific percentiles using the Hadlock, INTERGROWTH-21st, and World Health Organization reference standards. Correlations between ultrasound-based fetal weight percentiles and birth weight percentiles were assessed using Spearman's rank correlation coefficient.

RESULTS

Of 225 initially identified pregnancies, 179 fetuses were included in the final analysis, comprising 124 from women with systemic lupus erythematosus (69.3%) and 55 from controls (30.7%). Data distribution was non-normal. Across all growth standards, fetuses from women with systemic lupus erythematosus demonstrated lower mean weight percentiles than those from controls. Mean percentiles for controls versus the systemic lupus erythematosus group were 47.1% versus 38.4% using Hadlock, 63.3% versus 55.2% using INTERGROWTH-21st, and 51.7% versus 42.6% using World Health Organization. No statistically significant differences were observed among the three reference standards; however, INTERGROWTH-21st consistently yielded higher percentile values in both groups.

CONCLUSION

Although fetal weight classification varied according to the growth standard used, pregnancies complicated by systemic lupus erythematosus consistently exhibited lower fetal weight percentiles. Awareness of systematic differences among commonly used growth references is essential, as these may influence the detection of fetal growth restriction.