@schjo , the advice from the Tysabri Patient Information Leaflet is to consult with your Doctor "If you are pregnant or breast-feeding, think you may be pregnant or are planning to have a baby" So seeking professional advice from your Neuro and IVF Consultant is recommended. However, the following links should give you pause for thought:- https://wellandstrongwithms.com/2019/03/21/multiple-sclerosis-pregnancy/ https://www.webmd.com/multiple-sclerosis/news/20180208/ms-drug-poses-hard-choices-for-women-wanting-kids

I've read that tsyabri can be given up to the point of conception, and maybe up to the 3rd trimester if indicated. It's not recommended to breastfeed, however. It would be best to inform all health practitioners involved of what you're planning/medications. https://www.mstrust.org.uk/a-z/tysabri-natalizumab https://bnf.nice.org.uk/drug/natalizumab.html You might have to scroll down a bit on both to get to the pregnancy section. The BNF is what all UK healthcare professionals use for medicines.