pregnancy wedding dresses

I wonder if anyone has any experience of NMDA and pregnancy. My daughter has a dx of Autoimmune Encephalitis with NMDA antibodies still present. Her periods have recently stopped and blood and urine pregnancy tests come back negative although she has all the symptoms of early pregnancy and has just missed 2 periods. A repeat beta hcg blood test is being repeated in a week as the doctor is not convinced the last beta hcg test was accurate and suspects it was a false negative. Has anyone else experienced similar and can the NMDA antibodies affect HCG levels or blood tests? Thank you in advance pregnancy wedding dresses