Abstract
Objective
To estimate temporal changes in the prevalence of pre‐existing chronic conditions among pregnant women in Sweden and evaluate the extent to which secular changes in maternal age, birth cohorts and obesity are associated with these trends.
Design
Population‐based cross‐sectional study.
Setting
Sweden, 2002–2019.
Population
All women (aged 15–49 years) who delivered in Sweden (2002–2019).
Methods
An age–period–cohort analysis was used to evaluate the effects of age, calendar periods, and birth cohorts on the observed temporal trends.
Main outcome measures
Pre‐existing chronic conditions, including 17 disease categories of physical and psychiatric health conditions recorded within 5 years before childbirth, presented as prevalence rates and rate ratios (RRs) with 95% confidence intervals (CIs). Temporal trends were also adjusted for pre‐pregnancy body mass index (BMI) and the mother's country of birth.
Results
The overall prevalence of at least one pre‐existing chronic condition was 8.7% (147 458 of 1 703 731 women). The rates of pre‐existing chronic conditions in pregnancy increased threefold between 2002–2006 and 2016–2019 (RR 2.82, 95% CI 2.77–2.87). Rates of psychiatric (RR 3.80, 95% CI 3.71–3.89), circulatory/metabolic (RR 1.62, 95% CI 1.55–1.71), autoimmune/neurological (RR 1.69, 95% CI 1.61–1.78) and other (RR 2.10, 95% CI 1.99–2.22) conditions increased substantially from 2002–2006 to 2016–2019. However, these increasing rates were less pronounced between 2012–2015 and 2016–2019. No birth cohort effect was evident for any of the pre‐existing chronic conditions. Adjusting for secular changes in obesity and the mother's country of birth did not affect these associations.
Conclusions
The burden of pre‐existing chronic conditions in pregnancy in Sweden increased from 2002 to 2019. This increase may be associated with the improved reporting of diagnoses and advancements in chronic condition treatment among women, potentially enhancing their fecundity.
Keywords: chronic conditions, clinical epidemiology, maternal disease, pregnancy, pregnancy risk factors, prevalence
Short abstract
Linked article: This article is commented on by Merriel p. 53 in this issue. To view this article visit https://doi.org/10.1111/1471‐0528.17959.
1. INTRODUCTION
Globally, the prevalence of chronic conditions, such as diabetes, hypertension, asthma and psychiatric illness, is steadily increasing for all ages. 1 , 2 In the childbearing population, it remains one of the chief causes of maternal mortality and severe maternal morbidity. 3 , 4 , 5 , 6 Approximately one in ten pregnant women have a pre‐existing chronic condition during pregnancy, which may increase the complexity of obstetric care and require careful prenatal monitoring and timely obstetric intervention. 4 , 6 , 7 , 8 , 9
The chief reasons for the increasing prevalence of chronic conditions in the childbearing population remain unclear. 6 Possible explanations for this trend include the tendency towards delayed childbearing in high‐income countries. From 1999 through to 2019, the prevalence of advanced maternal age (≥35 years) in Sweden increased from 15.9% to 22.3%. 10 Similarly, occurrences of overweight and obesity have reached epidemic proportions globally, which have resulted in an increased burden of chronic conditions, including hypertension and pre‐existing diabetes mellitus. 11 , 12 In addition, it is estimated that the proportion of births to migrant women, including asylum seekers and undocumented immigrants, has doubled in high‐income countries, from 7%–8% in 1990 to approximately 13%–14% in 2017. 13 These immigrants are likely to have higher rates of multiple and complex health problems. 13 , 14 , 15 , 16
Only a few studies have investigated the prevalence of pre‐existing chronic conditions in pregnant women. 5 , 17 We estimated the temporal trend of pre‐existing medical conditions in relation to maternal age, period (delivery year) and (maternal) birth cohort effects over the study period in Sweden. We further evaluated the extent to which changes in obesity and immigration were associated with these trends.
2. METHODS
2.1. Study design and setting
We carried out a population‐based cross‐sectional study on all live births and stillbirths at ≥22 completed weeks of gestation in Sweden between 2002 and 2019. Data on these births were obtained from population‐based registers. The Swedish Medical Birth Register (MBR) includes prospectively recorded information on prenatal, delivery and neonatal care. The validity of most variables in the register has been assessed as being high. 18 Using the national registration number, a unique identity number assigned at birth or immigration and used in all public records, 19 the MBR was cross‐linked to several other national registers, including the National Patient Register (NPR, with nationwide information on inpatient care from 1987 and outpatient hospital care from 2001), 20 the Total Population Register (TPR, with information on demographic factors), 20 and the LISA database (with information on migration status). 21 At every visit, diagnoses are assigned by the attending physician, coded according to the International Classification of Diseases, ninth and tenth revisions (ICD‐9 and ICD‐10, respectively) and then recorded in the NPR. Diagnoses were coded with ICD‐9 codes prior to 1997, after which ICD‐10 codes were used. The NPR is more than 99% complete, and the same coding scheme is used for outpatient and inpatient information.
2.2. Maternal chronic conditions
We examined the prevalence of common chronic conditions associated with obstetric morbidity. 4 , 5 , 6 , 9 Analyses were focused on pre‐existing chronic conditions, diagnosed in the 5‐year period before conception (i.e. date of delivery minus gestational age), and these chronic conditions were identified using ICD‐9 and ICD‐10 codes (Table S1). We restricted the analysis to women aged 15–49 years and excluded 217 475 births (8.9%, of which <0.7% had ≥1 pre‐existing chronic condition) where the mother was not registered in Sweden for at least 4 years (of the 5 years) before the child's birth, to ensure that the data on maternal medical history was available. In total, we included 17 conditions: (i) psychiatric conditions (anxiety disorder, depression disorder, bipolar disorder, psychosis disorder and eating disorder); (ii) circulatory system/metabolic conditions (diabetes mellitus, hypertension, chronic heart disease, cerebrovascular disease and ischaemic heart disease); (iii) autoimmune/neurological conditions (epilepsy, rheumatoid arthritis, multiple sclerosis and systemic lupus erythematosus); and (iv) other conditions (inflammatory bowel disease, celiac disease and chronic kidney disease). All pre‐existing conditions were identified using a previously validated algorithm (Table S1), based on hospital diagnoses or outpatient physician diagnoses.
2.3. Maternal risk factors
We categorised the following maternal determinants of chronic illness: maternal age at delivery (15–19, 20–29, 30–34, 35–39, 40–44 and ≥45 years); early pregnancy body mass index (BMI, in kg/m2), classified as underweight (<18.5 kg/m2), normal (18.5–24.9 kg/m2), overweight (25.0–29.9 kg/m2), and obesity class I (30.0–34.9 kg/m2), class II (35.0–39.9 kg/m2) and class III (≥40 kg/m2); and mother's country of origin, categorised as Nordic, African, Asian, South American or Other.
2.4. Statistical analysis
We used delivery as the observation unit, including both live births and stillbirths (deliveries with twins and higher‐order multiple births were counted only once). Women with more than one delivery during the study period were included (see below).
Analyses were carried out to assess secular changes in pre‐existing chronic conditions, dividing the time span of the study into four periods (2002–2006, 2007–2011, 2012–2015 and 2016–2019) to improve the stability of the estimates. The magnitude of the change in the rate of maternal chronic conditions over time was estimated using log‐linear Poisson regression models with robust variance, with the rate ratio (RR) and 95% confidence interval (95% CI) as the effect measure. Period‐specific temporal changes in rates of pre‐existing chronic conditions were quantified using rate ratios with the periods 2002–2006 (i.e. the earlier period) and 2012–2015 (i.e. a more recent period) used as references. In the adjusted models, we examined how observed secular changes in maternal age, pre‐pregnancy BMI and mother's country of birth may have influenced the temporal changes in pre‐existing chronic conditions. To account for repeat pregnancies to the same woman, the model parameters were estimated based on generalised estimating equations. 22 To account for the correlation among repeated pregnancies to the same women, we used a robust sandwich estimator to correct standard errors in the analyses. Stratified analyses by parity (0 or ≥1) were also performed for each study period.
We performed an age–period–cohort (APC) analysis to evaluate temporal changes in rates of chronic conditions (overall as well as in the chronic condition subcategories) in relation to maternal age at delivery (age), delivery year (period) and maternal birth cohort (mother's birth year). 23 APC effects were estimated from weighted log‐linear Poisson models (annual rates), with constraints imposed to overcome the problem of colinearity in APC terms (cohort = period – age), and the weights were used as an offset term in the Poisson models.
We first included the age term to model the rates of chronic disease. This was followed by an overall linear trend in rates; this term reflects the sum of the linear component of period and cohort effects (also referred to as the ‘drift’ parameter, representing the average yearly change in rates). We then assessed deviations from linearity; these can be uniquely attributed to the period and cohort effects, which we refer to as the average ‘curvature’ effect. These parameter estimates can be interpreted as the direction and magnitude of the change in the linear trend by period and cohort. 24 All models were determined a priori and sequentially fitted, beginning with age only, then adding the drift parameter, and subsequently adding the period and cohort terms. We applied natural spline transformation for age, period and cohort (eight knots) to enable nonlinear smooth functions.
SAS 9.4 (SAS Institute, Cary, NC, USA) was used for data management and statistical analysis. The APC analysis was implemented in the Epi package using RStudio 1.2 (RStudio, Boston, MA, USA). 25
2.5. Patient involvement
This study was based on an analysis of information from linked databases and no patients were involved in designing the research question or the outcome measures, nor were they involved in developing plans for the implementation of the study. No patients were consulted for advice on the interpretation or drafting of the results.
2.6. Role of the funding source
The funders had no role in the study design, data collection, analysis, interpretation, writing the report or decision to submit the article for publication. The corresponding author had full access to the data and has final responsibility for data integrity and data analysis, and the decision to submit for publication.
3. RESULTS
The overall prevalence of women with one or more pre‐existing chronic condition in pregnancy was 8.7% (147 458 of 1 703 731 women). Women with chronic conditions in pregnancy were more likely to be younger (<20 years) or older (≥35 years), multiparous, have low education, live alone, be overweight or obese, or to smoke (Table S2). Anxiety disorders (4.4%), depression disorder (2.9%), diabetes mellitus (0.6%), epilepsy (0.4%) and inflammatory bowel disease (0.6%) were among the most common pre‐existing chronic conditions in pregnancy (Figure 1).
FIGURE 1.
Prevalence of pre‐existing chronic condition during pregnancy in Sweden.
The prevalence of one or more chronic condition in pregnancy increased considerably from 2002 (2.4%) to 2019 (12.0%) (Table S3). From 2002–2006 to 2016–2019, there was an almost threefold increase in the rate of any pre‐existing chronic condition in pregnancy (RR 2.82, 95% CI 2.77–2.87) (Table 1). The rates of psychiatric, circulatory/metabolic, autoimmune/neurological and other conditions increased substantially from 2002–2006 to 2016–2019. However, these increasing rates were less pronounced between 2012–2015 and 2016–2019.
TABLE 1.
Prevalence of pre‐existing chronic condition categories for all births in Sweden (2002–2019), stratified by periods.
| Conditions | 2002–2006 (n = 447 016) | 2007–2011 (n = 480 317) | 2012–2015 (n = 396 771) | 2016–2019 (n = 379 627) | 2016–2019 vs 2002–2006 | 2016–2019 vs 2012–2015 |
|---|---|---|---|---|---|---|
| No. (%) | No. (%) | No. (%) | No. (%) | RR (95% CI) | RR (95% CI) | |
| Composite of any disease | 18 902 (4.23) | 40 868 (8.51) | 42 422 (10.69) | 45 266 (11.92) | 2.82 (2.77–2.87) | 1.12 (1.10–1.13) |
| Psychiatric conditions | 10 589 (2.37) | 28 636 (5.96) | 31 447 (7.93) | 34 180 (9.0) | 3.80 (3.71–3.89) | 1.14 (1.12–1.15) |
| Anxiety disorder | 6695 (1.5) | 19 335 (4.03) | 22 433 (5.65) | 25 653 (6.76) | 4.51 (4.38–4.65) | 1.20 (1.17–1.22) |
| Depression disorder | 4730 (1.06) | 14 006 (2.92) | 15 460 (3.9) | 16 058 (4.23) | 4.00 (3.86–4.14) | 1.09 (1.06–1.11) |
| Bipolar disorder | 354 (0.08) | 1517 (0.32) | 2727 (0.69) | 3349 (0.88) | 11.1 (9.90–12.5) | 1.28 (1.22–1.35) |
| Psychosis disorder | 516 (0.12) | 804 (0.17) | 767 (0.19) | 782 (0.21) | 1.78 (1.58–2.01) | 1.07 (0.96–1.18) |
| Eating disorders | 464 (0.1) | 1579 (0.33) | 1715 (0.43) | 1854 (0.49) | 4.70 (4.18–5.29) | 1.13 (1.06–1.21) |
| Circulatory/metabolic conditions | 3377 (0.76) | 4765 (0.99) | 4338 (1.09) | 4657 (1.23) | 1.62 (1.55–1.71) | 1.12 (1.08–1.17) |
| Diabetes mellitus | 2213 (0.5) | 2829 (0.59) | 2536 (0.64) | 2839 (0.75) | 1.51 (1.42–1.61) | 1.17 (1.11–1.23) |
| Hypertension | 570 (0.13) | 1073 (0.22) | 1006 (0.25) | 1000 (0.26) | 2.07 (1.85–2.31) | 1.04 (0.95–1.13) |
| Chronic heart disease | 319 (0.07) | 558 (0.12) | 505 (0.13) | 569 (0.15) | 2.10 (1.81–2.44) | 1.18 (1.05–1.32) |
| Cerebrovascular disease | 293 (0.07) | 390 (0.08) | 374 (0.09) | 355 (0.09) | 1.43 (1.20–1.69) | 0.99 (0.86–1.15) |
| Ischaemic heart disease | 66 (0.01) | 83 (0.02) | 65 (0.02) | 48 (0.01) | 0.86 (0.57–1.29) | 0.77 (0.52–1.14) |
| Autoimmune/neurological conditions | 3140 (0.7) | 4915 (1.02) | 4448 (1.12) | 4506 (1.19) | 1.69 (1.61–1.78) | 1.06 (1.02–1.10) |
| Epilepsy | 1577 (0.35) | 2183 (0.45) | 1931 (0.49) | 1814 (0.48) | 1.35 (1.26–1.46) | 0.98 (0.92–1.05) |
| Rheumatoid arthritis | 1050 (0.23) | 1764 (0.37) | 1603 (0.4) | 1729 (0.46) | 1.94 (1.78–2.11) | 1.13 (1.05–1.21) |
| Multiple sclerosis | 270 (0.06) | 647 (0.13) | 612 (0.15) | 628 (0.17) | 2.74 (2.34–3.21) | 1.07 (0.96–1.20) |
| Systemic lupus | 280 (0.06) | 398 (0.08) | 345 (0.09) | 375 (0.10) | 1.58 (1.32–1.88) | 1.14 (0.98–1.31) |
| Other conditions | 2415 (0.54) | 4289 (0.89) | 4271 (1.08) | 4309 (1.14) | 2.10 (1.99–2.22) | 1.05 (1.01–1.10) |
| Inflammatory bowel disease | 1684 (0.38) | 2709 (0.56) | 2496 (0.63) | 2611 (0.69) | 1.83 (1.70–1.96) | 1.09 (1.04–1.15) |
| Celiac disease | 648 (0.14) | 1425 (0.3) | 1484 (0.37) | 1339 (0.35) | 2.43 (2.19–2.71) | 0.94 (0.87–1.02) |
| Chronic kidney disease | 108 (0.02) | 211 (0.04) | 334 (0.08) | 425 (0.11) | 4.63 (3.66–5.87) | 1.33 (1.15–1.53) |
The overall trend in ‘psychiatric conditions’ reflected trends in the two most common conditions, namely, anxiety disorder and depression disorder (Figure 2A; Table 1). Between 2002 and 2019, the prevalence rates of anxiety disorder (0.7%–7.0%), depression disorder (0.7%–7.0%), bipolar disorder (0.05%–0.9%) and eating disorder (0.06%–0.5%) increased substantially (Figure 2A; Table 1).
FIGURE 2.
Temporal trends of pre‐existing chronic condition among deliveries in Sweden, 2002–2019: (A) psychiatric conditions; (B) circulatory/metabolic conditions; (C) autoimmune/neurological conditions; and (D) other conditions.
The prevalence of ‘circulatory/metabolic conditions’ increased from 2002–2006 to 2016–2019 (RR 1.62, 95% CI 1.55–1.71). Stratified analyses showed that rates of diabetes mellitus and chronic heart disease increased steadily from 2002 to 2019 (Figure 2B; Table 1). The prevalence rates of hypertension increased from 0.05% in 2002 to 0.26% in 2012, and remained stable thereafter (Figure 2B; Table S3).
The prevalence of ‘autoimmune/neurological conditions’ increased from 0.44% in 2002 to 1.12% in 2019. During the corresponding period, the rate of rheumatoid arthritis increased from 0.24% to 0.43%, and the rates of epilepsy, multiple sclerosis and systemic lupus also increased. However, between 2012–2015 and 2016–2019, the prevalence rate of rheumatoid arthritis continued to rise, whereas the rates for epilepsy, systemic lupus erythematosus and multiple sclerosis remained stable (Figure 2C; Table 1). The increase in ‘other conditions’ was mainly associated with increases in inflammatory bowel disease and chronic kidney disease, where the rate of chronic kidney disease increased from 0.01% in 2002 to 0.12% in 2019 (Figure 2D; Table 1).
3.1. Age–period–cohort trends
The rate of ‘psychiatric conditions’ was high for maternal ages of <25 years, was lower in maternal age categories up to 35 years of age and increased thereafter (Figure 3). The rates of ‘circulatory/metabolic conditions’ increased sharply with maternal age, whereas the rates of ‘autoimmune/neurological conditions’ did not change with maternal age, and the rates of ‘other conditions’ declined till the mid‐20s and plateaued thereafter. Compared with deliveries in 2002, the rate ratio for psychiatric conditions increased on average by 8.4% (95% CI 8.2%–8.6%) per year (Figure 3). Compared with deliveries in 2002, the rate ratios for ‘circulatory/metabolic conditions’ and ‘other conditions’ increased steadily up to 2009, plateaued between 2009 and 2013, and increased thereafter. No birth cohort effect was evident for any of the pre‐existing chronic conditions (Figure 3).
FIGURE 3.
Age–period–cohort effects of pre‐existing chronic conditions, Sweden, 2002 to 2019. The rate of pre‐existing chronic conditions subgroups (per 100) is shown in relation to maternal age at delivery on the y‐axis on the left. The rate ratio (95% CI) of pre‐existing chronic conditions is shown in relation to the maternal birth cohort (with the 1975 maternal birth year as the reference), and period (with 2000 as the reference) on the right axis. The location of knots for the natural spline transformation for maternal age, period, and birth cohort is shown on the bottom and top axes. The long‐dashed line refers to psychiatric conditions, dotted lines refer to autoimmune/neurological conditions, dashed‐dotted lines refer to circulatory/metabolic conditions and the solid line refers to Other conditions.
3.2. Temporal trends in maternal risk factors
Between 2002 and 2019, the proportion of births to mothers aged 40–45 years increased from 2.7% to 4.0%, and the proportion of births to mothers aged ≥45 years increased from 0.1% to 0.3% (Table S4). From 2002 to 2019, the prevalence of obesity grade I among pregnant women increased in Sweden (7.8%–10.6%), and the rate of obesity grade III increased from 0.9% to 1.3% (Table S4). Birth to mothers born in Africa and Other countries also increased substantially during the study period (Table S4). However, adjustment for maternal age, pre‐pregnancy BMI and country of origin did not alter the temporal patterns (Table S5). Stratified analysis by parity revealed trends aligning with the main findings (Table S6).
4. DISCUSSION
4.1. Statement of principal findings
In this population‐based study including data from over 1.7 million births in Sweden, we have shown that the prevalence of any pre‐existing chronic condition in pregnancy has increased almost threefold over the past 18 years. Most chronic conditions increased during the study period, and the most common pre‐existing chronic conditions were anxiety disorder, depression disorder, diabetes mellitus, epilepsy and inflammatory bowel disease. Adjusting for secular changes in maternal age, obesity and mother's country of birth did not affect these associations. Rates of circulatory and metabolic conditions increased almost linearly with maternal age, whereas psychiatric conditions showed a U‐shaped relationship with maternal age. We observed no birth cohort effect for any of the chronic conditions.
4.2. Strengths and weaknesses of the study
The population‐based study with prospectively collected information on maternal conditions helps to minimise measurement bias and selection bias. The analysis, which attempts to distinguish age, period and cohort effects, revealed insights into temporal trends in chronic conditions both overall and within specific subcategories. The identification of each chronic condition was based on a previously validated algorithm. In general, the validity of diagnoses is high in the Swedish registers. 26
Some limitations need to be considered when interpreting our results. Long‐term trends of different conditions may have been influenced by secular changes to the screening process and diagnostic criteria for some specific conditions during the study period. This cross‐sectional study, although valuable for its longitudinal perspective, is inherently subject to limitations, particularly concerning changes in screening practices over time. The accuracy and validity of diagnoses relies on the reliability of the ICD codes, which may vary across time and by version of ICD classification. Hence, our ascertainment of maternal conditions may have been limited to more cases and resulted in an underestimation of prevalence. The exclusion of women not registered in Sweden before cohort entry should also be considered when interpreting our results. These women, likely to be new immigrants or undocumented migrants, may have different rates of chronic illness and maternal characteristics. 27 Additionally, in our study the prevalence among the excluded group was low (<0.7%), suggesting the presence of prevalence underestimation bias. Lastly, we did not perform analyses adjusting for smoking or other potential covariates such as infertility treatment.
4.3. Comparison with other studies
The temporal increase in maternal chronic conditions observed in our study is consistent with the findings of a study from Denmark, 5 reporting a fourfold increase in maternal chronic conditions in pregnancy in 2009–2013, compared with 1989–1993. Furthermore, the APC analysis of the chronic condition subcategories showed maternal age and period effects, and absent birth cohort effects. The strong linear association between maternal age and rates of ‘circulatory/metabolic conditions’ and the nonlinear relationship with ‘psychiatric conditions’ is likely to be influenced by biological factors. The increases in conditions such as anxiety and bipolar disorder by period may reflect an increased recognition of such morbidity over time, and the potential for medical treatments to alleviate these conditions. On the other hand, a secular increase in diabetes could reflect changes in environmental factors, such as diet or exercise. 28 , 29 Other possible explanations for the observed period effects could be improvements in medical care, leading to the normalisation of pregnancy among women with chronic conditions, and increases in the fecundity of these women, with the widespread and increasing availability of assisted reproduction.
Higher rates of mental health conditions diagnosed among childbearing women have previously been reported. 8 In our study, the rate of psychiatric conditions increased on average by 8% per year during the study period. Increasing rates of psychiatric conditions is consistent with a US study, which reported that the proportion of delivery hospitalisations with one or more mental health conditions increased by more than 10‐fold from 2000 to 2018. 8 Additionally, these mental health conditions have been reported to be increasingly associated with underlying chronic health conditions, such as diabetes mellitus, obesity, chronic hypertension or asthma. 8 Our findings parallel the trends observed in British Columbia, Canada, where the prevalence of hypertension sharply rose from 0.06% in 2000 to 0.3% in 2019. 17
We also observed increasing rates of autoimmune and neurological conditions, such as multiple sclerosis and rheumatoid arthritis, possibly owing to advances in the treatment and management of women with chronic conditions, which have increased the fecundity of such women. The increasing rate of chronic kidney disease in our study is concerning, as a recent study in Sweden showed an increase in the rate of acute renal failure and dialysis in pregnancy and postpartum, from 0.6 per 10 000 in 1999 to 1.7 per 10 000 in 2019. 30 Similar increases in the rate of acute renal failure have been reported previously in the USA, 31 and also in Canada. 17 , 32
Two US studies, investigating the prevalence of several circulatory and metabolic conditions during childbirth in the past three decades (1989–2018), also demonstrated a rising prevalence of hypertension and diabetes. 33 , 34 Furthermore, in line with our findings, substantial increases of pregnancies complicated by type 1 and type 2 diabetes have been reported in both Sweden and Scotland. 35 , 36 Maternal diabetes increases the risks of fetal anomalies, macrosomia and birth injury, which can influence developmental outcomes in the offspring. 37 Timely and appropriate interventions are therefore key elements to optimise pregnancy outcomes in this high‐risk pregnant population.
In addition, the co‐occurrence of two or more chronic conditions is an emerging concern among pregnant women, with the prevalence increasing from 25% in 2003 to 32% in 2016, 6 , 38 and with one in five women having multimorbidity in the year before pregnancy. 39 There exists a dose–response relationship between pre‐existing chronic conditions and risk of severe maternal morbidity, with women with three or more comorbidities having a ten times higher risk of severe maternal morbidity. 40 Maternal chronic conditions also increase the risk of short‐term adverse birth outcomes (such as preterm birth, low birthweight and stillbirth), which could be caused by the chronic disease itself, 7 , 41 or by medication for the chronic disease. 42 Therefore, from a healthcare system perspective, any maternal chronic condition calls for more coordinated multispecialty care during pregnancy. More research is needed to understand the impact of pre‐existing chronic illness on maternal and child health and to improve preconception counselling and disease management before and during pregnancy. Future studies should examine the causes underlying the temporal changes that we observed (i.e. the maternal characteristics and health system factors responsible).
5. CONCLUSION
The temporal burden of pre‐existing chronic conditions in pregnancy has increased in the last 18 years. Maternal age was strongly associated with both psychiatric conditions and circulatory/metabolic conditions. The high prevalence of chronic conditions in the childbearing population calls for an increase in pre‐conceptional services, and more coordinated multispecialty care in pregnancy.
AUTHOR CONTRIBUTIONS
LL and NR had full access to all data in the study and take full responsibility for the integrity of the data and the accuracy of the data analyses. Study concept and design: LL and NR. Acquisition of data: NR. Drafting of article: LL. Critical revision of the article for important intellectual content: LL, CVA, KSJ, SC and NR. Statistical analysis: LL and NR. Obtained funding: NR.
FUNDING INFORMATION
The study was supported by grants from the Swedish Research Council for Health, Working Life and Welfare (4‐2702/2019).
CONFLICT OF INTEREST STATEMENT
All authors have completed the ICMJE uniform disclosure form at www.icmje.org/coi_disclosure.pdf and declare: no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous 3 years; and no other relationships or activities that could appear to have influenced the submitted work.
ETHICS APPROVAL
The study was approved by the Ethics Review Authority at the Karolinska Institutet, Stockholm, Sweden (2020–01545).
Supporting information
Table S1.
Table S2.
Table S3.
Table S4.
Table S5.
Table S6.
ACKNOWLEDGEMENTS
None.
Lundborg L, Ananth CV, Joseph KS, Cnattingius S, Razaz N. Changes in the prevalence of maternal chronic conditions during pregnancy: A nationwide age–period–cohort analysis. BJOG. 2025;132(1):44–52. 10.1111/1471-0528.17885
Linked article: This article is commented on by Merriel p. 53 in this issue. To view this article visit https://doi.org/10.1111/1471‐0528.17959.
DATA AVAILABILITY STATEMENT
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available owing to privacy or ethical restrictions.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Table S1.
Table S2.
Table S3.
Table S4.
Table S5.
Table S6.
Data Availability Statement
The data that support the findings of this study are available on request from the corresponding author. The data are not publicly available owing to privacy or ethical restrictions.