Is there a way to initialize members of a struct without using a constructor?

I have a struct that contains two lists:

struct MonthData
{
   public List<DataRow> Frontline;
   public List<DataRow> Leadership;
}

However, I want to initialize both when the struct is created. If I try:

struct MonthData
{
   public List<DataRow> Frontline = new List<DataRow>();
   public List<DataRow> Leadership = new List<DataRow>();
}

Then I get:

Error   23  'MonthData.Frontline': cannot have instance field initializers in structs
...

Since structs cannot have parameterless constructors, I can't just set this in a constructor either. So far, I can only see the following options:

1. Initialize both properties when I create an instance of MonthData
2. Use a class instead of a struct
3. Create a constructor with a parameter and use that
4. Make getters and setters for the properties that initialize them lazily.

What is the recommended approach for this? Right now, I'm thinking making this a class is the best idea.