Pre-pregnancy obesity among immigrant and non-immigrant women in Norway: Prevalence, trends, and subgroup variations

Abstract

Introduction: This study assessed prevalence and time trends of pre-pregnancy obesity in immigrant and non-immigrant women in Norway and explored the impact of immigrants' length of residence on pre-pregnancy obesity prevalence.

Material and methods: Observational data from the Medical Birth Registry of Norway and Statistics Norway for the years 2016-2021 were analyzed. Immigrants were categorized by their country of birth and further grouped into seven super regions defined by the Global Burden of Disease study. Pre-pregnancy obesity was defined as a body mass index ≥30.0 kg/m², with exceptions for certain Asian subgroups (≥27.5 kg/m²). Statistical analysis involved linear regressions for trend analyses and log-binomial regressions for prevalence ratios (PRs).

Results: Among 275 609 pregnancies, 29.6% (N = 81 715) were to immigrant women. Overall, 13.6% were classified with pre-pregnancy obesity: 11.7% among immigrants and 14.4% among non-immigrants. Obesity prevalence increased in both immigrants and non-immigrants during the study period, with an average yearly increase of 0.62% (95% confidence interval [CI]: 0.55, 0.70). Obesity prevalence was especially high in women from Pakistan, Chile, Somalia, Congo, Nigeria, Ghana, Sri Lanka, and India (20.3%-26.9%). Immigrant women from "Sub-Saharan Africa" showed a strong association between longer residence length and higher obesity prevalence (≥11 years (23.1%) vs. <1 year (7.2%); adjusted PR = 2.40; 95% CI: 1.65-3.48), particularly in women from Kenya, Eritrea, and Congo.

Conclusions: Prevalence of maternal pre-pregnancy obesity increased in both immigrant and non-immigrant women from 2016 to 2021. Several immigrant subgroups displayed a considerably elevated obesity prevalence, placing them at high risk for adverse obesity-related pregnancy outcomes. Particular attention should be directed towards women from "Sub-Saharan Africa", as their obesity prevalence more than doubled with longer residence.

Keywords: early pregnancy complications; epidemiology; low‐income country; maternity care; obesity; pregnancy; women's health issues.

FIGURE 1

Study sample flowchart. BMI, body mass index.

FIGURE 2

Maternal pre‐pregnancy obesity (BMI ≥30.0 kg/m²) prevalence by country of birth. Results are given for subgroups contributing with 200 or more births during the study period 2016–2021. Immigrants from “Southeast Asia, East Asia, and Oceania” and “South Asia” were categorized using a lower BMI threshold (≥27.5 kg/m²) as described in the methods. Adjusted PR with 95% CI was estimated for each country of birth, using the non‐immigrants as the reference category. The PR was adjusted for year of childbirth, maternal age, parity, educational level, and Norwegian health region. The corresponding crude PRs with 95% CIs are shown in Table S2. BMI, body mass index; CI, confidence interval; GBD, Global Burden of Disease; PR, prevalence ratio.

FIGURE 3

Time trends in maternal pre‐pregnancy obesity (BMI ≥30.0 kg/m²) prevalence in non‐immigrants and immigrants categorized by region of birth (GBD). Immigrants from “Southeast Asia, East Asia, and Oceania” and “South Asia” were categorized using a lower BMI threshold (≥27.5 kg/m²) as described in the methods. Annual percentage changes in obesity with 95% CI were estimated using linear regression models. The corresponding adjusted percentage changes with 95% CIs, adjusted for year of childbirth, maternal age, parity, educational level, and Norwegian health region, are shown in Table S3. BMI, body mass index; CI, confidence interval; GBD, Global Burden of Disease.

FIGURE 4

Maternal pre‐pregnancy obesity (BMI ≥30.0 kg/m²) prevalence by length of residence in immigrants categorized by region of birth (GBD). Immigrants from “Southeast Asia, East Asia, and Oceania” and “South Asia” were categorized using a lower BMI threshold (≥27.5 kg/m²) as described in the methods. Adjusted PR with 95% CI was estimated for each time interval, using the shortest length of residence as the reference category (<1 year). The PR was adjusted for year of childbirth, maternal age, parity, educational level, and Norwegian health region. The crude and adjusted PRs with 95% CIs are also shown in Table S4. BMI, body mass index; CI, confidence interval; GBD, Global Burden of Disease; PR, prevalence ratio.