During pregnancy, oestrogen and progesterone levels are increased. Consequently 
the initial predominant immune cellular response (Th1 type) is decreased, 
whereas humoral response (Th2 type) is increased. Due to this switch, a lot of 
Th2 anti-inflammatory cytokines IL-4 and IL-10 are synthesized. During the last 
months of pregnancy Treg lymphocytes level is elevated leading to overexpression 
of IL-4 and IL-10. Due to these mechanisms, reduce disease activity of 
rheumatoid arthritis (RA) occurred. Impaired fertility has not been demonstrated 
in women with RA. However, some studies suggest that polyarthritis could induced 
a reduced weight at birth and more frequent pregnancy and delivery 
complications. Methotrexate and biotherapies have demonstrated no effect on 
fertility; however these drugs must be stopped before conception for a period 
equal to seven fold of the half live of the molecule. No teratogenic effect are 
known for sulfazalasine and hydroxychloroquine; these drugs could be used during 
pregnancy. It is also the same for ciclosporine, which used is quite unfrequent 
in RA. Methotrexate is teratogenic in animal models and is forbidden during 
pregnancy. For leflunomide which is metabolised in A771726, highly teratogenic, 
a washout period of 3,5 months is necessary. All commercially available TNFalpha 
inhibitors are classified by the food and Drug Administration as pregnancy risk 
category B: no adverse pregnancy adverse effects have been observed in animal 
studies, but there have been insufficient controlled human studies. The 
published experiences with TNFalpha inhibition in pregnancy is limited to some 
case reports and ongoing registry. More recently some cases of Vater syndromes 
(polymalformations) were possibly related to TNFalpha blocking agents. Such 
treatment must be avoided during pregnancy. Only few case reports are published 
concerning rituximab use during pregnancy. No data have been found for 
abatacept.