(HealthDay)—Well-child visits (WCVs) at 15 months, 18 months, and four years are the most commonly missed among children of low-income families, according to a study published online Oct. 10 in Pediatrics.

Elizabeth R. Wolf, M.D., M.P.H., from the Virginia Commonwealth University in Richmond, and colleagues retrospectively studied 152,418 (aged 0 to 6 years) seen at two health networks in 20 states between 2011 and 2016. Adherence to the 13 American Academy of Pediatrics-recommended WCVs from birth to age 6 years was assessed.

The researchers found that most children were either publicly insured (77 percent) or uninsured (14 percent). The most frequently attended visits included the two-, four-, and six-month visits (63 percent with no outside care after the last recorded WCV and 90 percent with outside care). The least frequently attended were the 15- and 18-month visits (41 to 75 percent) and the four-year visit (19 to 49 percent). Patients who were publicly insured and uninsured had higher odds of missing WCVs versus privately insured . Hispanic and Asian-American patients had higher odds of attending WCVs versus non-Hispanic white patients.

"Across patients of different races and with different insurance types, WCVs at 15 , 18 months, and at four years were the most commonly missed," the authors write. "Children who missed these visits may lack developmental screenings and other preventive services typically performed at these ages."