Objective. To study reproductive performance and interaction between a
nkylosing spondylitis (AS) and pregnancy in a large population of fema
le patients. Methods. In collaboration with the Ankylosing Spondylitis
International Federation, a questionnaire including clinical data and
details on past and recent pregnancies was sent to the female members
of national and regional AS societies in the USA, Canada, and 11 Euro
pean countries. Results. Nine hundred thirty-nine questionnaires were
completed, showing the following clinical data. Mean age at onset of A
S was 23 years. The onset was related to a pregnancy in 21%. The frequ
ency of accompanying features of AS was as follows: peripheral arthrit
is 45%, acute anterior uveitis 48%, psoriasis 18%, and inflammatory bo
wel disease 16%. Six hundred forty-nine women with previous pregnancie
s had on average 2.4 pregnancies per woman, of which 1.4 pregnancies w
ere during disease. Of pregnancies 15.1% ended with miscarriage. Disea
se activity during 616 previous and 366 recent pregnancies was unchang
ed in 33.2%, improved in 30.9%, and worsened in 32.5%. Improvement of
disease activity during pregnancy was correlated with a history of per
ipheral arthritis. It was also observed more often among those having
a female than a male child (p = 0.02), A postpartum flare within 6 mon
ths after delivery was experienced by 60%, most often patients with ac
tive disease at conception. Delivery occurred at term in 93.2% of case
s. The rate of cesarean section was high and due to AS in 58% of cases
. The majority of neonates were healthy and had a mean birthweight of
3339 g. AS had an adverse effect on being a mother and a caregiver. Co
nclusion, AS did not adversely affect fertility, pregnancy outcome, or
the neonate. Improvement during pregnancy was related to a history of
peripheral arthritis and a female fetus. Active disease at conception
was a predictor of a postpartum flare.