This is a multi-country, prospective safety study of pregnant women exposed to efgartigimod or efgartigimod PH20 SC any time within 25 days prior to conception or any time during pregnancy. Women exposed to efgartigimod or efgartigimod PH20 SC only during breastfeeding will also be eligible to enroll. Background rates of major congenital malformations (MCMs) will be obtained from populations within the same countries/regions as the countries/regions in which the efgartigimod or efgartigimod PH20 SC exposed pregnancies were reported.

Inclusion Criteria:

• Women with exposure to efgartigimod or efgartigimod PH20 SC any time within 25 days prior to conception or any time during pregnancy, or women with exposure to efgartigimod or efgartigimod PH20 SC during breastfeeding. The timeframe of 25 days prior to conception is calculated based on five times the efgartigimod half-life, which is 3 to 5 days.
• Written/verbal informed consent or eConsent (depending on country regulations) (for adolescents under the age of majority, written/verbal informed assent or eConsent by the pregnant minor (where applicable) and written/verbal informed consent or eConsent by the parent/legal guardian).

Exclusion Criteria:

• None

Pregnant women or women no longer pregnant at the time of study enrollment but exposed to efgartigimod any time within 25 days prior to conception or any time during the pregnancy.