(225) Evaluation for congenital infections in late-onset small for gestational age (SGA) neonates

Symmetric SGA neonates are thought to be small due to familial, genetic, or infectious causes. The association of maternal infections with early-onset SGA is controversial and SMFM recommends against screening for congenital infections in SGA in the absence of other risk factors (strong recommendation, low-quality evidence). We have evaluated the utility of routine investigation for late-onset symmetric SGA infants.

Study Design:

Cohort study of all infants with birth weight < 10^th centile born at >35 weeks over a 2-year period (2021-2022). Symmetric SGA was defined as both birth weight and head circumference < 10 centile. Excluded were infants with congenital anomalies, genetic syndromes, and those transferred to high acuity neonatal intensive care units. Birth weight centile were evaluated according to Fenton growth curves to include late preterm infants. SGA infants were recommended testing for congenital infections, head ultrasound (US), complete blood cell count, and glucose testing.

Results:

Of the 6075 babies born at >35 weeks during the study period, 339 (5.6%) were SGA and 116 of them (34%) were symmetric SGA. Urine CMV PCR was done on 67/116 (58%) babies with symmetric SGA, and all results were negative. TORCH IgM/Total IgM was done on 65 babies (56%), and only 1 had a mild elevation in Total IgM. Head US was done on 67 babies (58%); it was normal in 60 (89%). Seven babies had abnormal US findings: 2 with increased echogenicity in the periventricular matter, 1 with small periventricular calcifications, and 4 with grade 1 IVH (one of which had a small periventricular calcification).  Repeat head US or brain MRI 3 months later was normal. Urine CMV PCR was negative in all these babies. 

Conclusion: Extensive laboratory work-up for congenital infections in symmetric SGA babies at >35 weeks is not useful or cost effective.