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From the little that you have told us, I don't think we have, or have had, any member of this community in circumstances like your own. We have had several mothers in this community that have died from SCLS, but they were in their 40s or 50s when first diagnosed, so their children were already born. Therefore, I'm just going to give you some rather general advice.
First, the bad news is that SCLS is a deadly illness of unknown causes; the good news is that it usually responds well to a preventive monthly treatment of injected immunoglobulins (IVIG).
Second, there is considerable medical experience with SCLS in France, much more so than in any other country relative to size, so I suggest that you schedule a visit to Paris to get confirmation of your diagnosis and answers to all your questions from experts like Drs. Zahir Amoura or Marc Pineton de Chambrun at the Hôpitaux Universitaires La Pitié salpêtrière - Charles Foix, see https://www.aphp.fr/offre-de-soin/consultation-37726
Third, although there is still a lot that we don't know about SCLS, one of the things we do know is that SCLS is NOT hereditary. Therefore, once your health has been stabilized, you don't have to fear that any children you give birth to will also get SCLS. Many of us are parents and even grandparents, and our children and grandchildren do NOT have SCLS. (And our parents and grandparents didn't have SCLS, either.)
And fourth, if you have been given a tentative diagnosis of a deadly disease, and you are NOT being treated successfully for it, then obviously this is NOT a good time for you to put your body through any trauma (like pregnancy and delivery) that you can postpone. And since you are very young, you can certainly postpone pregnancy and childbirth.
If you were my daughter, I would try to convince you that the best thing you can possibly do before even thinking about getting pregnant is to get healthy, or at least medically stable, yourself before you must care for a newborn.