Yes, you can upgrade straight from September 2018 to April 2019. However, I would suggest upgrading to June 2019 instead. I've found that it has been much more stable.
With that said, it's always good to take back ups so you can roll back if anything goes awry.
One thing you may find is that some extensions may break. I usually tend to thoroughly test all extensions after an upgrade incase any API changes deprecated the functionality.
