Spontaneous abortion (SA), classified under ICD-10 code O03 and commonly referred to as miscarriage, is a prevalent complication in early pregnancy, with incidence rates varying depending on population characteristics and study methodologies (1, 2). Research indicates that approximately 10% to 20% of clinically recognized pregnancies worldwide result in SA, with higher rates observed when early pregnancy losses are included (3, 4). The majority of these losses occur in the first trimester (5, 6). In Kazakhstan, a study involving 237 participants reported that 25.6% of respondents had experienced SA (7). A large-scale national study analyzing 207,317 records of women across all regions of Kazakhstan estimated the prevalence of spontaneous pregnancy loss before 22 weeks of gestation to be 8.7%, with a 20% decline observed over the 2014–2019 period (8).

Several factors have been associated with an increased risk of SA. Advanced maternal age is a significant risk factor, as chromosomal abnormalities in embryos are more common in older women (9, 10). A cross-sectional study in Astana, Kazakhstan (2015–2017), analyzing 67,759 inpatient records, found advancing maternal age significantly increased the risk of miscarriage, with women aged 30–39 and 40+ years having 54% and 272% higher risks, respectively compared to women aged 19–29 years (11). Moreover, maternal obesity has been linked to higher miscarriage rates, potentially due to hormonal imbalances and metabolic disturbances, with risks ranging from 1.25 to 2.25 times higher compared to normal-weight women (12–14). Another important factor in early pregnancy loss is the history of SA and pre-pregnancy health. Studies have shown that a history of SA significantly increases the risk of subsequent losses, with women who have experienced one or more miscarriages being at higher risk for recurrence (15, 16). Inadequate pre-pregnancy health, including suboptimal management of chronic conditions, poor nutritional status, and lack of preconception care, has been linked to adverse pregnancy outcomes (17). Lifestyle factors prior pregnancy, including smoking and alcohol consumption, have also been implicated in elevating miscarriage risk (18, 19).

Building on these findings, it becomes clear that preconception may play an important role in addressing the modifiable risk factors associated with early pregnancy loss (20). Preconception care, as defined by the World Health Organization, includes a set of biomedical, behavioral, and social interventions provided to women and couples before conception to improve maternal and fetal outcomes (21). It aims to identify and mitigate risk factors such as obesity, unmanaged chronic conditions, and inadequate nutritional status while promoting healthier lifestyle choices (22). The benefits of preconception care are well-documented, with evidence indicating that it can help reducing the incidence of adverse pregnancy outcomes, including SA, preterm birth, and congenital anomalies (23). Targeted preconception interventions, such as weight management, smoking cessation, and folic acid supplementation, have been shown to improve pregnancy outcomes and reduce healthcare costs by preventing complications before conception (24).

This study aimed to investigate the socio-demographic and clinical risk factors associated with SA in the first trimester and evaluate the protective effects of preconception care among women in Kazakhstan, largest country in Central Asia. It adds a global health perspective and highlights the importance of addressing disparities in maternal health outcomes, an essential aspect of public health research. While previous studies have extensively documented risk factors for spontaneous abortion, there is limited research on the role of preconception care in mitigating these risks, particularly in low- and middle-income countries (LMICs), and some finding can be extrapolated to all Central Asian countries.

For practical healthcare, a key conceptual issue is the variability of risk factors for spontaneous miscarriage, as potentially modifiable factors can form the basis for clinical or preventive interventions in pregnancy management. However, given that most miscarriages occur in the early weeks of pregnancy, sometimes even before a woman knows she is pregnant, addressing these factors at this stage may be too late for any intervention or treatment to influence the outcome. This highlights the need to identify high-risk individuals before conception to implement appropriate preventive measures aimed at reducing the risk (32).

We assessed the socio-demographic and clinical risk factors for first-trimester spontaneous abortion. Our results showed that the odds of first-trimester SA were higher in women over 35 years of age compared to women under 35 [[OR] = 2.02, 95% [CI] = 1.49–2.75]. This finding is consistent with previous research (33–35). The decline in reproductive potential in older women may be attributed to reduced oocyte quality, changes in the endometrium, and altered progesterone levels (36). Although age is a non-modifiable risk factor at the individual level, especially in cases of unintended pregnancies, it can be considered a modifiable risk factor at the population level. Including this factor in risk assessments can help prevent underestimating the risk of miscarriage in this population.

Furthermore, a strong negative impact of high BMI on pregnancy outcomes was observed [[OR] = 1.81, 95% [CI] = 1.12–2.91]. The risk of SA among women with obesity in our study aligns with findings from previous studies (37, 38). Possible mechanisms include poor endometrial receptivity, a pro-inflammatory state caused by cytokines, hormonal imbalances, or impaired blood supply to the endometrium and placenta (39–41). Further research is needed to confirm these theories. Early weight loss interventions may reduce the risk of SA in obese patients. Public health policies targeting obesity prevention can significantly improve women's reproductive outcomes (42). Such interventions should adopt a multisectoral approach addressing social, structural, economic, and environmental factors. Raising awareness among women about the importance of lifestyle changes and modifiable risk factors is necessary for reducing the overall risk of SA and other adverse maternal and infant health outcomes (12, 43–45).

We also found that women with a history of SA had an increased risk of first-trimester SA [[OR] = 1.57, 95% [CI] = 1.01–2.43], consistent with prior research indicating a significantly higher risk in this group (33). While previous pregnancy loss is a non-modifiable factor, including it in risk assessments can prevent underestimating the risk in these populations.

An important finding of our study was that women who received preconception care had a lower risk of first-trimester SA [[OR] = 0.58, 95% [CI] = 0.45–0.75] compared to those who did not receive preconception care. This reinforces the conclusion that preconception care improves pregnancy outcomes (46). The preconception period offers a critical window for intervention, empowering women at higher risk of SA to address modifiable risk factors before conception (47). Potential mechanisms for reducing the risk of early pregnancy loss include optimizing chronic disease management, correcting nutritional deficiencies, normalizing weight, reducing harmful exposures, preventing infections, and taking folic acid, which aligns with meta-analysis findings (18, 48). These all highlight the need for national initiatives to improve the health of women of childbearing age before planned pregnancies. In Kazakhstan, the importance of preconception care has been recognized with the implementation of a new clinical protocol in 2,023, providing comprehensive guidelines for healthcare providers to ensure its effective delivery (49). This protocol emphasizes the screening for chronic diseases, nutritional deficiencies, lifestyle modifications, vaccination, psychosocial support, counseling, and education to prepare couples for the emotional and physical challenges of pregnancy and parenthood.

The primary strength of this study is that, to the best of our knowledge, it is the first to investigate preconception care as a factor influencing first-trimester SA in women in Kazakhstan. Similar studies have been conducted in high-income countries with advanced healthcare systems, such as the United States and the United Kingdom, focusing on risk factors for early pregnancy loss and the broader implications of miscarriage (50, 51). Our study, conducted in Kazakhstan, applies to other Central Asian countries due to similar healthcare systems and their classification as middle-income economies. The analysis included a large sample of 1,526 women, which strengthens the statistical power and reliability of the results. These findings guide clinical counseling on spontaneous abortion risks and the public health benefits of preconception care. The study shows that preconception care protects against early pregnancy loss, providing clear support for clinical practice and public health efforts to improve pregnancy outcomes. This makes the results relevant for shaping policies and allocating resources. Integrating preconception care into routine health services, especially in low- and middle-income countries with limited access to such interventions, addresses modifiable risk factors like obesity and advanced maternal age. Such efforts improve maternal and neonatal health, lower healthcare costs, and promote health equity.

In addition to the factors identified in our analysis, long-term changes in the reproductive system, including hormonal disturbances, may also influence pregnancy outcomes. Emerging data suggest that some of these changes may be associated with prior COVID-19 infection, potentially affecting menstrual cycle regularity, ovulatory function, and endometrial receptivity (52–54). Although the clinical significance of these observations requires further clarification, including such variables in future studies will enhance understanding of the mechanisms underlying adverse pregnancy outcomes and support the development of more precise preventive strategies.

From a public health perspective, the study has several limitations. First, selection bias is possible: the data were obtained from a single regional hospital with two perinatal centers that admit medium- and high-risk patients, and records with incomplete data were excluded. Second, information bias is possible: data and outcomes were extracted from an electronic medical database, and several covariates were missing, such as income, smoking, alcohol use, gestational age, antenatal complications, use of assisted reproductive technologies, or male factors (55, 56). Third, residual bias remains, since assignment to preconception care was not randomized, and exclusion of records with missing data may introduce selection bias if missingness is related to both exposure and outcome. The study period coincided with COVID-19 waves, which could have affected access to care, health-seeking behavior, and the structure of recorded cases. The moderate discriminative ability of the model (ROC-AUC ≈0.62) suggests that the results are most useful for assessing associations and planning prevention at the population level rather than for individual risk prediction. In addition, binary dichotomization of the outcome does not capture the severity of perinatal outcomes among live births and excludes late fetal or neonatal deaths. Future research should apply composite or ordinal perinatal endpoints. Finally, the reliance on retrospective data from medical records may underestimate the true prevalence of risk factors, particularly for socially sensitive or less commonly documented variables such as lifestyle behaviors or preconception care practices.

In our study, we evaluated associations between candidate factors and spontaneous abortion in the first trimester. Age >35 years, obesity, and a history of spontaneous abortion were associated with higher odds of early pregnancy loss, whereas preconception care was associated with lower odds. These findings expand the understanding of preventive measures taken before pregnancy in relation to adverse outcomes in the first trimester. In clinical practice, they may support risk stratification and counseling of women who could benefit from targeted preventive or therapeutic interventions before conception. From a public health perspective, the observed association with preconception care should be interpreted as associative rather than causal, and further prospective studies are needed before drawing conclusions about its impact on maternal and neonatal outcomes.