The goal of this observational study is to learn about consequences for the child when the mother is treated with rituximab (or other monoclonal CD-20 antibodies) before or during pregnancy. The main questions it aims to answer are:

• Is the infant's immune system effected with lower levels of B-cell markers, higher rates of infections or poor vaccine response?
• Are the monoclonal CD20-antibodies fully eliminated in women treated within 6 (12) months prior to conception?

Participants will:

• At the time of clinical routine blood sampling (at the end of each trimester) the becoming mother will give some additional blood samples for analysis of drug concentration
• Within the first year postpartum the child will leave a blood sample to detect antibodies induced by vaccination or infections
• Within our routine contacts with the participant (mother) will be asked about infections in both the mother and the child

In offspring to women with MS and current pregnancies the investigators will address if a reduction in the levels of KREC (kappa-deleting recombination excision circles) and/or CD19+ B-cells at birth has clinical significance. Participants with MS regardless of treatment that have successfully delivered or will deliver a child will be asked for informed consent and after given informed consent they will be included in the study.

1. At the time of clinical routine sampling in the becoming mother the investigators will collect additional blood samples. Routine analysis collects information on immunoglobulin levels and b-cell levels, additional blood samples will allow analysis of drug concentration at the end of every trimester.
2. Within the first year postpartum, but earliest one month after vaccination, the investigators will ask for a blood sample from the child to detect antibodies induced by vaccination or infections to secure the ability to develop antibodies despite being exposed to monoclonal CD20-antibodies in-utero or via breastmilk. All children followed by the Specialist outpatient clinic for children in Liljeholmen - a specialist clinic from the Karolinska University Hospital following children to mothers on immunosuppressant/immunomodulating treatments regardless of disease, will be offered blood sampling by routine months 2, 6 and 1 year postpartum. In collaboration with this center, the investigators will get samples taken and analyzed within clinical routine.
3. PKU-test is taken in the child within routine but additional analysis on drug levels and KREC will be analyzed as well as determining abundance of CD19 transcripts.
4. Within the routine contacts with the MS patient (mother) the investigators will ask for infections in both, the mother and the child at 3 months and 1 year post-partum.

Inclusion Criteria:

• Established multiple sclerosis diagnosis
• Rituximab, ocrelizumab, ofatumumab or other monoclonal CD-20 antibody has been administered within 6 (12) months prior to or during pregnancy
• Other immun modulation treatment has been administered within 6 (12) months prior to or during pregnancy
• No treatment has been administered within 6 (12) months prior to or during pregnancy

Exclusion Criteria:

- Previous stem cell transplantation

Able to become pregnant and deliver a child

Women diagnosed with multiple sclerosis that are patients at the Academic specialist center, Center for Neurology, Stockholm, Sweden

We plan to share all pseudoanonymised IPD that underlie results in a future publication.