forms.js

const serialize = function (data) {
  const formData = new FormData();
   
  for ([key, value] of Object.entries(data)) {
    Array.isArray(value)
      ? value.forEach(v => formData.append(key, v))
      : formData.append(key, value);
  }
  
  return formData;
}

# ...
const csrfToken = document.querySelector('input[name="csrfmiddlewaretoken"]').value;

fetch("/pacientes", {
  method: 'POST',
  body: serialize(data),
  headers: {
    'X-CSRFToken': csrfToken 
  }
})
.then(res => res.json())
.then(json => {
  json.ok ? window.location.href = json.redirect_url
});