Background/Purpose:

• Offspring of patients with chronic inflammatory arthritis have almost double the risk of being born small for gestational age. Placental insufficiency is one of the common causes of reduced fetal growth and low birth weight, it is unclear if maternal chronic inflammatory arthritis directly affects placental dysfunction.
• Placental weight is an indicator of placental development and growth, we investigated placental and birth weights of offspring born to women with rheumatoid arthritis and juvenile idiopathic arthritis (RA/JIA).

Methods:

• We used data from several linked population-based clinical registries in Denmark, from years 2008 – 2018 to identify the study population of interest. We used ICD-10 codes contained within the Danish National Patient Registry to identify pregnant women diagnosed with RA/JIA before and during pregnancy. The Danish Fetal Medicine Database provided details of gestational ages, placental weights and birthweights of singleton offspring born to women with and without RA/JIA. Missing gestational ages were obtained from the Danish Medical Birth Registry.
• We performed linear regression analysis comparing the mean placental weights and standard deviations (SD) of male and female offspring born between 34 and 42 weeks of gestation, among women with and without RA/JIA. The estimated mean differences were adjusted for confounders, including gestational age at birth and sex of offspring. All analyses were performed using RStudio version 2022.12.0.

Results:

• Our study population included 2,279 women with RA/JIA who had singleton pregnancies. Women diagnosed with RA/JIA were more likely to be older than 35 years of age at the time of pregnancy (21.7% vs. 16.8%), had pre-pregnancy BMI between 25 to < 30 (24.2% vs. 21.8%), a higher frequency of C-section deliveries (25.5% vs. 20.0%), and co-morbidities before and during pregnancy (Table 1).
• The overall mean ± SD placental weight of women with RA/JIA vs without RA/JIA were 656.3g (± 148.1g) vs 675.7g (± 148.0g) in male offspring; 646.07g (± 151.6g) vs 662.8g (± 145.7g) in female offspring. The overall mean ± SD birthweight of male offspring born to women with and without RA/JIA was 3,492.4g (± 572.7g) vs 3,574.0g (± 557.9g); mean birthweight of female offspring was 3,365.9g (± 574.6g) among women with RA/JIA vs 3,450.8g (± 574.6g) among women without RA/JIA.
• The mean placental weights of male and female offspring born to women with RA/JIA were overall lower compared to women without RA/JIA at 35 weeks gestational age and beyond, although the placental weights of female offspring seemed to be comparable at 42 weeks among both groups of women (Figure 1).
• The adjusted mean difference in placental weight among offspring of women with RA/JIA vs without (reference), was -16g (95%CI -9.8, -22; p< 0.001)] (Table 2).

Conclusion:

• Placental weights of offspring born to women with RA/JIA were overall lower compared to women without RA/JIA, however the weight difference was modest.
• Our findings open the door for further mechanistic studies to evaluate if placental pathology, or other factors may be contributing to adverse pregnancy outcomes in this population.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/placental-weights-of-offspring-born-to-women-with-rheumatoid-arthritis-and-juvenile-idiopathic-arthritis/