Mod of inheritance of very rare disease

Hello Dr.
I am the mother of three children diagnosed with Primary Pulmonary Hypoplasia. Familial cases of bilateral PPH are exceptional. It is a disease incompatible with life, and my husband and I are entirely asymptomatic, pointing to an autosomal recessive mode of inheritance. No one knows for certain.
The few familial cases of PPH that exist in the literature point to consanguinity. My husband and I are not remotely related. And because three out of three children have been affected, we have our doubts about the mode of inheritance (in our particular case).
I am currently three and a half months pregnant via a sperm donor; I conceived this baby before learning of gonadal mosaicism. I am now sick with worry thinking I am the asymptomatic carrier, with a high volume of mutated cells in my ovaries.
I was wondering if you could tell me the following: just based on odds, in a case in which three out of three children are effected with a familial condition that is quite rare, and both parents are unrelated, would an autosomal mode of inheritance still be a more likely mode of inheritance, or is this a good indication gonadal mosaicism is more likely? In general, what are the odds in a situation like this that a mutation is coming from one of the parents, as opposed to both?

[tuti]

Autosomal recessive is the likely mode of inheritance. This baby does ot have PPH.