Adverse neonatal outcomes in migrant women in Norway

Abstract

Background: With increasing international migration, more knowledge is needed regarding migrant women’s pregnancies and births. Migrant families represent great diversity and investigating the risk of adverse neonatal outcomes in sub-groups of migrant women is therefore vital. Overall aim: To investigate associations between migration related factors (maternal country of birth, paternal origin, reason for immigration, length of residence and country of a woman’s first birth) and adverse neonatal outcomes (very preterm birth, moderately preterm birth, post-term birth, small for gestational age, large for gestational age, low Apgar score, stillbirth and neonatal death) in migrant and non-migrant women giving birth in Norway. Material and methods: All three papers are based on population-based register studies. Data were retrieved from the Medical Birth Registry of Norway and Statistics Norway. We investigated associations between: (1) migration related factors (maternal country of birth, paternal origin, reason for immigration, length of residence, and birthplace of firstborn child) and stillbirth in births to migrant and non-migrant women (1990-2013); (2) country of a woman’s first birth and adverse neonatal outcomes (very preterm birth (22+0-31+6 gestational weeks), moderately preterm birth (32+0-36+6 gestational weeks), post-term birth (≥42 gestational weeks), small for gestational age, large for gestational age, low Apgar score (<7 at 5 minutes), stillbirth and neonatal death) in multiparous migrant and non-migrant women (1990-2016); and (3) paternal origin and adverse neonatal outcomes (very preterm birth, moderately preterm birth, low Apgar score and stillbirth) in migrant women (1990-2016). Associations were investigated using multiple logistic regression and reported as adjusted odds ratios (aORs) with 95% confidence intervals (CI). Analyses were performed separately for primiparous and multiparous women. Results: Paper 1: Primiparous women from Sri-Lanka and Pakistan, and multiparous women from Pakistan, Somalia, the Philippines and the Former Yugoslavia had higher odds of stillbirth when compared to non-migrant women (adjusted ORs ranged from 1.58 to 1.79 in primiparous and 1.50 to 1.71 in multiparous women). Primiparous migrant women whose babies were registered with a Norwegian-born father had decreased odds of stillbirth compared to migrant women whose babies were registered with a foreign-born father (aOR = 0.73; CI 0.58–0.93). Primiparous women migrating for work or education had decreased odds of stillbirth compared to Nordic women who migrate freely between the Nordic countries (aOR = 0.58; CI 0.39–0.88). Multiparous migrant women who gave birth to their first baby before arriving in Norway had higher odds of stillbirth in later births in Norway compared to multiparous migrant women who had had their first baby after arrival (aOR = 1.28; CI 1.06–1.55). Length of residence in Norway was not associated with stillbirth. Paper 2: Multiparous migrant women with a first birth before immigration to Norway had increased odds of adverse outcomes in subsequent births relative to those with a first birth after immigration: very preterm birth (aOR=1.27; CI 1.09-1.48), moderately preterm birth (aOR=1.10; CI 1.02-1.18), post-term birth (aOR=1.19; CI 1.11-1.27), low Apgar score (aOR=1.27; CI 1.16-1.39) and stillbirth (aOR=1.29; CI 1.05-1.58). Similar results were found in births to Norwegian-born women who had their first baby abroad. Paper 3: Compared with births to migrant women with a foreign-born partner, births to migrant women with a Norwegian-born partner were associated with lower ORs for very preterm birth (primiparous: aOR 0.83; 95% CI 0.73-0.96, multiparous: aOR 0.85: 95% CI 0.73-0.98), stillbirth (primiparous: aOR 0.68; 95% CI 0.55-0.86, multiparous: aOR 0.80; 95% CI 0.64-0.99), and low Apgar score (multiparous: aOR 0.87; 95% CI 0.80-0.96). Unregistered paternal origin and unknown paternal identity were both associated with increased odds of adverse neonatal outcomes. Conclusion and clinical implications: The risk of adverse neonatal outcomes varied across sub-groups of migrant women and was higher in women from a number of countries, multiparous women who had their first baby before immigration to Norway, women whose babies had foreign-born fathers and births where paternal origin was unregistered or paternal identity was unknown. Specifically, the risk of stillbirth was lower in primiparous women who had migrated for work or education compared to Nordic migrants who are permitted to migrate freely between the Nordic countries. Stillbirth was not associated with length of residence in Norway. This thesis highlights the need to improve care for sub-groups of migrant women at increased risk of stillbirth and other adverse neonatal outcomes. The results should serve as a reminder of the diverse needs of migrant women, and the importance of midwives and other health care providers collecting a thorough obstetric history in migrant women attending maternity care services.