The Affordable Care Act, Medicaid and the Children’s HealthInsurance Program have driven the uninsured rate among children to historic lows,but millions of U.S. kids still go without important healthservices, according to a new study.

The study by the Children’s Health Fund finds a quarter ofAmerican kids lack access to crucial healthcare. That translates to just over 20 million individuals under age18.

Critical services include vaccinations, annual physicals,treatment of acute or chronic pain, mental health care and dental care.

Those missing out on such services include the country’s 3.3million uninsured children as well as millions who are covered by afamily health plan.

The top barrier to health care, above all else, is cost. It’sobviously a big issue for those who lack insurance, but it’s also aproblem for those with health plans with high deductibles orco-pays.

Those who depend on Medicaid or ACA plans also have a hard timefinding providers who will accept their insurance. As a result,many low-income Americans in rural areas have to travel longdistances to get basic health care. In urban areas transportationcan be a barrier as well if a doctor who accepts the patient’sinsurance isn’t accessible by public transit.

Technology offers an opportunity to help patients who arestruggling to find providers in their area. Practices that areputting in place telemedicine options, such as video consultationswith patients, can help ease the financial and transportationburdens that prevent many low-income patients from taking time outof their day to go to the doctor’s office. They also make it mucheasier to squeeze a doctor’s consultation into a busy workschedule.

The impending repeal of the ACA has advocates for child health care nervous. While it was farfrom perfect from their perspective, Obamacare offered families ofmodest means an easy way to buy insurance.

“(N)one of the proposed replacements will do anything tomitigate what children would potentially lose if the A.C.A. isactually repealed,” Dr. Irwin Redlener, the study author, tells theNew York Times.

While ACA plans’ sticker prices are often high, the greatmajority of enrollees receive subsidies that substantially reducetheir premiums and out-of-pocket costs. What the repeal of the ACAwill mean for millions of low and middle-income families thatcurrently get coverage through Healthcare.gov largely depends onwhat Trump and Congressional Republicans decide to put in place inits stead. So far, that remains unclear.