Background/Purpose:

Pregnancy often exacerbates systemic rheumatic diseases, and systemic rheumatic diseases often lead to adverse obstetric outcomes. Both rheumatic disease activity and adverse obstetrical outcomes are associated with alterations in B cells . To date, circulating levels of BAFF, a vital B cell survival factor, have not been serially evaluated in pregnancy. Accordingly, we  assessed maternal and cord blood serum levels of BAFF and  evaluated whether first-trimester BAFF levels are associated with adverse pregnancy outcomes. 

Methods:

Blood samples were collected from pregnant women with non-anomalous singleton intrauterine pregnancies receiving care at a single medical center.  Participants were classified as “healthy” (n = 33), “medical disease” (n = 34), or “rheumatic disease” (n = 5) based on the presence/absence of medical or rheumatic conditions.  Age-matched non-pregnant women (n = 5) served as controls.  Pregnant participants had blood samples collected at least once per trimester, at delivery, and postpartum. Additionally, cord blood was collected at delivery.  Non-pregnant subjects had a single blood draw.  Samples were assayed for BAFF by ELISA. Levels in women who developed spontaneous abortion (SAB; pregnancy loss prior to 20 weeks gestation), hypertensive disorders of pregnancy (HDP), or preterm delivery (PTD) were compared with levels in women without these adverse events.

Results:

Median BAFF levels between “healthy” and “medical disease” participants did not differ significantly, whereas levels were elevated in women with rheumatic conditions (p=0.04).  Median (interquartile range) first, second, and third trimester, cord blood, and postpartum BAFF levels (ng/ml)in women without rheumatic diseases were 0.63 (0.45-3.95), 0.53 (0.45-1.02), 0.59 (0.45-1.03), 1.95 (0.61-4.54), and 0.76 (0.45-1.41), respectively.  In women with rheumatic conditions, levels were 0.76 (0.69-2.02), 0.78 (0.544-0.99, 0.60 (0.45-0.99), 1.14 (0.70-2.07), and 0.74 (0.45-0.97), respectively.  Second and third trimester BAFF levels were significantly decreased compared to first trimester and postpartum BAFF levels (p<0.01 for each) in the women without rheumatic diseases, whereas levels did not significantly differ across trimesters among women with rheumatic conditions.  Cord blood levels for all women were significantly elevated compared with any trimester level (p<0.001 for each). In contrast to the decrease in BAFF levels seen in women in the second trimester without HDP, BAFF levels increased between the first and second trimester in women who developed HDP (p<0.01). First trimester BAFF levels were not significantly associated with HDP (p=0.26) or PTD (p=0.82), whereas a trend towards significance was noted with SAB (p=0.051). 

Conclusion:

Elevated first-trimester BAFF levels may be associated with SAB.  Moreover, the loss of the normal decline in BAFF levels between the first and second trimesters may be associated with the development of HDP.  Additional subjects and samples are being collected and analyzed to confirm these initial observations. If confirmed, serum BAFF may be a useful biomarker in the management of pregnancy.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/b-cell-activating-factor-baff-and-pregnancy-outcomes/