Principal Findings
ART such as IVF and ICSI are commonly used in infertility treatments, more and more infertility patients have been able to conceive using ART[12], however, ART does not prevent and avoid spontaneous abortion. In fact, prevention and premanagement of spontaneous abortion is more important than treatment[13, 14]. Therefore, it is important to correctly assess and identify the risk factors for spontaneous abortion and conduct clinical intervention as early as possible. Our study explored the risk factors of spontaneous abortion in patients receiving ART, univariate and multivariate logistic regression analysis showed that female age, male age, basic FSH, and AMH were independent risk factors for spontaneous abortion. In addition, we successfully constructed a nomogram prediction model based on the above independent influencing factors, and these findings can provide preventive and personalized interventions for clinicians and infertile couples. The aim of this study was to analyze and construct a nomogram model based on big clinical data to identify abortion risk factors, we quantified, visualized and graphed the results of logistic regression, and calculated the value of variables by analyzing the graph, so as to predict the probability of abortion in patients treated with ART. The nomogram model is more intuitive to show the prediction results, and its AUC is 0.746 (95%CI = 0.707–0.784), which shows that it has good prediction accuracy and specificity. Different from other clinical models of assisted reproduction in the past, nomogram is more intuitive and practical, which is convenient for clinicians to calculate the probability of abortion in ART treatment cycle according to patients' own conditions.
Results
Previous studies have pointed out that ART does not increase the risk of spontaneous abortion[15, 16], the spontaneous abortion rate among ART pregnancies was 14.7%. There was a 10.1% spontaneous abortion risk among women 20–29 years old and a 39.3% spontaneous abortion risk among women older than 43, the spontaneous abortion risk was 13.1% among pregnancies conceived with donor eggs[17]. This conclusion was similar to a Chinese study, a large Chinese study in 2017 showed that the incidence of early pregnancy loss in ART patients receiving fresh embryo transfer was 14.9%[18]. In addition, it has been shown that the incidence of early spontaneous abortion after ART is about 10.6%[19]. Regardless of the specific data about spontaneous abortion, this is quite a high percentage considering the time-consuming and money-taking on ART. However, research currently shows that the causes of miscarriage are not fully understood[20, 21], and there are few methods of prevention and intervention. Furthermore, there is no predictive model that can be used to guide clinical treatment based on the individual parameters and laboratory data of such patients. For assisted reproduction experts, it is imperative to minimize spontaneous abortion. In view of this, we screened out independent risk factors and establish an accurate prediction model for predicting the probability of miscarriage, in order to better guide the clinical application and provide better treatment options for infertility patients.
Clinical Implications
According to our study, female age is an independent predictor of spontaneous abortion and is positively correlated with it, a spontaneous abortion is more likely to occur at an older age. It is well known that the quality and number of oocytes decrease with age[22, 23], the ATP content in the cytoplasm decreases, and the proportion of abnormal embryos chromosome structure increases[24]. The number of pregnant women over 35 years old who spontaneously aborted in patients receiving ART was significantly higher than that of pregnant women under 35[25]. In addition, as women age, their endometrial receptivity decreases and abnormal blood flow occurs, which are causes of an increase in spontaneous abortion[26]. Similarly, in our study, we found that male age is an independent risk factor for spontaneous abortion in ART patients. A meta-analysis of 975 original clinical studies showed that spontaneous abortion are associated with advanced paternal age, the pooled risk estimates for spontaneous abortion for age categories 30–34, 35–39, 40–44 and ≥ 45 years of age were 1.04 (95% CI 0.90, 1.21), 1.15 (95% CI 0.92, 1.43), 1.23 (95% CI 1.06, 1.43) and 1.43 (95% CI 1.13, 1.81) respective[8]. In another study involving patients with natural conception, spontaneous abortion risks increased by 1.26 times in men over 35 years of age, and they were not influenced by alcohol consumption[27]. Despite the difference in target population, the findings were similar to our own. In a study by Kleinhaus et al., spontaneous abortion risk in males > 40 years of age was 1.6, independent of female age and other factors[28]. In addition, Frattarelli et al. found that spontaneous abortion increased with the age of the father, among those over 50, spontaneous abortions were 41.5%, and among those under 50, they were 24.4%[29]. With the increase of age, there are a variety of factors associated with increasing age that will destroy the DNA replication and repair mechanism and increase the possibility of DNA breakage, causing abortions, which leads to abortion[30, 31]. The relationship between male age and the probability of spontaneous abortions could provide genetic counseling for older men.
Research Implications
As we presented above, this study found that female age and male age were independent risk factors for spontaneous abortion. Apart from the above, we found that basic FSH and AMH are also important factors contributing to spontaneous abortions during ART. In assisted reproduction (ART), when ovarian reserve decreases, basic FSH levels increase, while AMH levels decrease[32, 33]. The ovarian reserve and endometrial conditions are essential to the implantation and growth of embryos[34], therefore, fluctuations in hormone levels can lead to spontaneous abortions. In addition, poor ovarian reserve may induce us to use more follicle stimulating hormone during ART, large doses of follicle stimulating hormone affect the level of female endocrine hormones and the oocyte quality[35, 36]. Based on these research results and the Nomogram model, we can predict the probability of spontaneous abortions based on the results of laboratory examinations and the individual parameters of infertile patients in ART.
Strengths And Limitations
Our study has some strengths. First, to our knowledge there is no report indicating logistic regression-based nomogram model that has been used to predict the risk factors of spontaneous abortion in infertile patients treated with ART, thus, our study is innovative in this field. Second, our sample size is relatively large and the analysis was comprehensive compared with previous studies. Third, in this analysis, we present the target independent variables as both categorical variables and continuous variables, which reduces the amount of contingency in the analysis and enhances its robustness. Our study has the major limitation of being retrospective, which cannot exclude all possible biases, selection bias can skew results in some ways. In addition, although the nomogram model can better predict the probability of spontaneous abortion and provide reference for clinicians and patients, but no nomogram model is perfect. In the future, larger cohort studies and better data collection methods are needed to improve the prediction accuracy of nomogram model.