Pregnancy outcomes in women with immunoglobulin A nephropathy: a nationwide population-based cohort study

BACKGROUND: Immunoglobulin A nephropathy (IgAN) incidence peaks in childbearing age. Data on pregnancy outcomes in women with IgAN are limited. METHODS: We performed a register-based cohort study in a nationwide cohort of women with biopsy-verified IgAN in Sweden, comparing 327 pregnancies in 208 women with biopsy-verified IgAN and 1060 pregnancies in a matched reference population of 622 women without IgAN, with secondary comparisons with sisters to IgAN women. Adverse pregnancy outcomes, identified by way of the Swedish Medical Birth Register, were compared through multivariable logistic regression and presented as adjusted odds ratios (aORs). Main outcome was preterm birth (< 37 weeks). Secondary outcomes were preeclampsia, small for gestational age (SGA), low 5-min Apgar score (< 7), fetal or infant loss, cesarean section, and gestational diabetes. RESULTS: We found that IgAN was associated with an increased risk of preterm birth (13.1% vs 5.6%; aOR = 2.69; 95% confidence interval [CI] = 1.52–4.77), preeclampsia (13.8% vs 4.2%; aOR = 4.29; 95%CI = 2.42–7.62), SGA birth (16.0% vs 11.1%; aOR = 1.84; 95%CI = 1.17–2.88), and cesarean section (23.9% vs 16.2%; aOR = 1.74, 95%CI = 1.14–2.65). Absolute risks were low for intrauterine (0.6%) or neonatal (0%) death and for low 5-min Apgar score (1.5%), and did not differ from the reference population. Sibling comparisons suggested increased risks of preterm birth, preeclampsia, and SGA in IgAN, but not of cesarean section. CONCLUSION: We conclude that although most women with IgAN will have a favorable pregnancy outcome, they are at higher risk of preterm birth, preeclampsia and SGA. Intensified supervision during pregnancy is warranted. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s40620-021-00979-2.