The course of ankylosing spondylitis during pregnancy: intermediate data of a prospective follow-up
Authors: Krichevskaya O. A. , Gandaloeva Z. M. , Demina A. B. , Dubinina T. V. 
Published: May 2019

The onset of ankylosing spondylitis (AS) more frequently occurs at the end of the third decade of life, which corresponds to the time of marriage and the birth of the first child and determines the relevance of a study of the interaction of AS and pregnancy.

Objective:to describe the clinical presentations of AS and its therapy during pregnancy and to study AS activity dynamics and the patients' functional status during gestation.

Patients and methods. The investigation enrolled 19 pregnant women who met the 1984 modified New York AS criteria. The mean age of the women was 32.2±1.1 years; their mean age at the onset of AS was 22.6±3.1 years; the duration of the disease was 147±20.7 months. The patients visited their physician at 10–11, 20–21, and 31–32 weeks of pregnancy. The investigators determined AS activity by the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and the Ankylosing Spondylitis Disease Activity Score (ASDAS) and functional status by the Bath Ankylosing Spondylitis Functional Index (BASFI) and the Bath Ankylosing Spondylitis Metrology Index (BASMI). The Maastricht Ankylosing Spondylitis Enthesitis Score (MASES) was used to assess enthesitis.

Results and discussion. At the time of conception, 78.9% of the patients had inflammatory back pain with an intensity of 2.2±0.4 on a numerical rating scale; during pregnancy, 95% of the pregnant women experienced pain, its intensity increased by the second trimester (4.6±0.7) and remained at this level in the third trimester (p<0.05 between the month of conception and the second and third trimesters). By the third trimester, the nature of the pain changed: 55.5 and 61.1% of the patients reported reduced pain at rest and after exercise, respectively. The frequency and severity of enthesitis increased with gestational age: the MASES scores were higher in the third trimester (2.3±0.5) than that in the first-trimester (0.4±0.22; p<0.05). The frequency of extra-axial and extra-skeletal manifestations did not increase during gestation. Coxitis was detected in 27.8% of the pregnant women.

The BASDAI increased from the time of conception (1.7±0.3) to the second trimester (3.3±0.5; p<0.05) and remained at this level in the third trimester. Multiple regression analysis revealed that the predictors of BASDAI levels in the third trimester were BASDAI scores (R2 =0.7) and back pain (R2 =0.9) at the time of conception, the use of biological agents 3 months before gestation (R2 =0.7) with their cumulative impact. Throughout pregnancy, the BASDAI was determined by a set of factors: the severity of pain in the back (β=0.6) and entheses (β=0.3) and weakness (β=0.6). By the end of the first trimester, the increased BASDAI scores were provided mainly by the higher level of general weakness (by 68.5%) and back pain (by 24.1%). In the second trimester, the higher BASDAI was due to the increased severity of enthesitis (by 30.7%) and back pain (by 27%).

There were no changes in ASDAS-C-reactive protein (ASDAS-CRP), but there was its upward tendency in the second trimester as compared with the beginning of pregnancy. The BASMI did not change significantly (1.3±0.9; 1.8±0.2; 2.1±0.3, respectively, for trimesters). The BASFI increased by the third trimester (3.9±0.7) versus the first trimester (1.4±0.3; p<0.05).In the third trimester, this rise was due to difficulties in performing the actions related to both AS activity and pregnancy (forward bends; questions 1, 2, and 4).

According to the trimesters, 31.6, 73.7, and 66.7% of the pregnant women took nonsteroidal anti-inflammatory drugs. The need for glucocorticoids was noted in 22% of patients in the second trimester and in 53% in the third trimester.

Conclusion.The clinical activity of AS is increased by the second trimester of pregnancy and remains moderate and high until the end of gestation. The activity of AS at the time of conception can determine the activity of the disease throughout pregnancy. In the third trimester, mechanical back pain becomes concurrent in half of the patients. Functional impairments increase with gestational age, and this is due to both the activity of AS and pregnancy itself in the third trimester.