Introduction:
Both discolored amniotic fluid and oligohydramnios increase the risk of adverse pregnancy outcomes, such as stillbirth, and a combination of the two is more severe than an isolated one. Immigrant women in certain sub-groups are at an increased risk of adverse pregnancy outcomes, including stillbirth. The aim of the study was to investigate associations of maternal country of birth with discolored amniotic fluid, oligohydramnios and stillbirth.

Material and Methods:
This is a nationwide population-based study including immigrant (N=304 853) and Norwegian-born women (N=1 355 174) giving birth in Norway in 1990-2021. Data were obtained from the Medical Birth Registry of Norway and Statistic Norway. Multivariable logistic regression analyses were used to estimate odds ratios (OR) with 95% confidence intervals (CIs). Analyses were adjusted for year of birth, maternal age, parity, maternal education and income.

Results:
In overall analyses, higher odds for stillbirth were found in births with isolated discolored amniotic fluids (aOR 3.39; 95% CI 3.21-3.58), isolated oligohydramnios (aOR 5.72; CI 5.12-6.37) and births registered with both discolored amniotic fluids and oligohydramnios (aOR 13.38; CI 11.88-15.08), compared to births without these conditions. Compared to Norwegian-born women, births to immigrant women showed higher odds for isolated discolored amniotic fluid (OR 1.22; CI 1.20-1.23), isolated oligohydramnios (aOR 1.19; CI 1.16-1.23) and the combination of discolored amniotic fluids and oligohydramnios (aOR 1.42; CI 1.35-1.48). Sub-groups of immigrant women were either associated with higher or similar odds of isolated discolored amniotic fluid or the combination of discolored amniotic fluid and oligohydramnios, compared to Norwegian-born women. In particular, women from Sub-Saharan Africa were associated with an increased odds of all three outcomes; isolated discolored amniotic fluids (aOR 1.29; 95% CI 1.23-1.35), isolated oligohydramnios (aOR 1.99; CI 1.89-2.09) and births registered with both discolored amniotic fluids and oligohydramnios (aOR 3.05; CI 2.81-3.30), compared to Norwegian-born women.

Conclusions:
Discolored amniotic fluid, oligohydramnios, or a combination of both increase stillbirth risk. Most sub-groups of immigrant women, especially those from Sub-Saharan Africa, are at higher risk of all three outcomes compared to Norwegian-born women. In this study, the combination of discolored amniotic fluid and oligohydramnios was associated with particularly high odds for stillbirth and should therefore require close monitoring during labour. Future research should aim to increase knowledge on the causes and risk factors for these conditions and develop strategies to prevent associated stillbirths.