Introduction
The adverse outcome of pregnancy can affect the quality of life of the baby and the mother in the short and long term, despite the mental and emotional damage (1). In addition, it can also cause the imposition of medical expenses, which in many cases, considering the amount of family income, becomes difficult for parents to manage it (2). The use of screening methods is expanding nowadays. Based on the progress of knowledge and also according to the physiological and clinical processes of the mother, different screening methods have been developed during the first to third trimesters of pregnancy (3). Based on the data, the use of screening methods today has resulted in preventing the birth of fetuses with genetic or developmental abnormalities. Also, the use of screening methods will detect abnormalities on time and ultimately reduce costs for families and the health system (4).
Today, many markers are used to screen fetuses in the first to third trimester of pregnancy. The evaluation of these markers is based on non-invasive methods and includes total β-HCG, unconjugated estriol, Alpha Feto Protein (AFP), and Dimeric Inhibin A (DIA) in Second Trimester Screening (STS) and Pregnancy-Associated Plasma Protein (PAPP-A) and free β-HCG in First Trimester Screening (FTS) (5,6).
PAPP-A is a type of metalloproteinase that stimulates cell growth and plays a role in regulating the biological activity of Insulin-like Growth Factors (IGF). This enzyme plays an important role in the development of the fetus and placenta. Low serum concentration of PAPP-A in maternal circulation is an important sign of early placental insufficiency in the first trimester of pregnancy. However, its effects on the fetus reach a detectable level in the second trimester (7). Growth failure determined in the second trimester of pregnancy is also directly related to adverse neonatal and pregnancy outcomes (8). Several studies have reported that low levels of PAPP-A may increase the risk of placenta-related pregnancy complications such as Intrauterine Growth Restriction (IUGR), Preterm Labor (PTD), and spontaneous abortion (9). In pregnant women who are at risk of chromosomal disorders, the serum PAPP-A level is low (10). Therefore, in this study, the relationship between the serum PAPP-A level and genetic abnormalities in newborns was examined. 

Materials and Methods
Design study
Available data were used in this retrospective cohort study. The research population was made up of women with a history of pregnancy referring to Tajrish Martyrs’ Hospital in 2018, which was approximately 15,000 people. All the prenatal aneuploidy screening tests of these patients were done in Nilou Medical Laboratory a referral Laboratory in Tehran, Iran. 

Patient selection criteria
Included criteria were being Iranian, singleton, age between 18-40 years old, gestational age 11-14 weeks based on ultrasound in the first trimester of pregnancy, no history of gestational diabetes, no history of type 1 and 2 diabetes, no obvious diabetes, no history of a baby weighing 4 kg or more, no history of pre-eclampsia, eclampsia, high blood pressure, no history of stillbirth, no history of an abnormal baby or fetus and repeated abortion, no smoking and drug use, and no use of assisted reproduction methods. It was in the current pregnancy. Exclusion criteria included violations in records or unwillingness of patients to continue cooperation.

Data collection
The data was collected using a checklist that was prepared in advance. Based on this, the demographic data of the patients was collected. Data collection was done in two parts. The researcher collected information related to the research by referring to the hospital archive and studying the patients’ files.   If a file did not have the desired information or was incomplete, it was excluded from the study. In the next part, the researcher had a phone call with each sample and collected some data from the patients through interviews.

Statistical analysis
The collected data was analyzed by SPSS v.22 software. The Kolmogirov-Smirnov test was used for the normality of the data. Descriptive statistics (mean, standard deviation, frequency, and percentage) were used to report demographic variables. To check the quantitative variables from the t-test, to check the qualitative variables from the chi-square test, to check the ranked variables from the Mann-Whitney test (for non-parametric data), and to check the probability of pregnancy complications in the normal and abnormal PAPP-A group, the relative risk was calculated. ROC analysis was used to assess the association between PAPP-A MoM with total adverse outcomes and chromosomal abnormalities. A p-value of less than 0.05 was considered significant.

Results
Evaluation of PAPP-A cut-off in patients
In this study, PAPP-A cutoff was divided into three categories: <0.27, 0.27-2.99, and >=3. Based on the results, it was shown that the average PAPP-A in the three categories was 1.01±1.73, 1.64±0.73, and 1.59±0.34, respectively. The results showed that these differences were statistically significant (p=0.003). Additionally, the PAPP-A MoM level compares the final risk of Down syndrome across three groups: low risk (risk less than 1:1500) to the extent of 7162 (47.7%), intermediate risk (risk between 1:251 and 1:1500) to the extent of 2660 (17.7%), and high risk (risk greater than or equal to 1:250) to the extent of 5188 (34.6%).

Results of descriptive information of patients
The following table shows the demographic and descriptive information of the patients. In terms of gender, the sex of the fetuses was female in 51% of cases. In terms of chromosomal abnormalities 18 and 21, most of the patients were in the low-risk category. Also, in terms of maternal and fetal outcomes and chromosomal abnormalities, the percentage of each is shown in table 1.

Evaluation of chromosomal abnormalities and outcomes based on maternal serum PAPP-A levels
The results show that most of the patients with chromosomal abnormalities had a PAPP-A level of <0.27 (p<0.001). It was found that the group of patients whose PAPP-A level was > or =3 had the highest structural anomaly (p=0.021). On the other hand, the highest maternal adverse outcomes [such as Premature Rupture of Membranes (PROM), pre-eclampsia, abortion, polyhydramnios, oligohydramnios, amniotic leakage, bleeding, and blood spotting] were in patients whose PAPP-A level was <0.27 (p<0.001). No significant difference in adverse fetal outcomes was observed in the above three groups (p=0.61). Overall, the incidence of chromosomal disorders, structural abnormalities, and adverse pregnancy outcomes in both the mother and fetus was higher in the group with PAPP-A levels below 0.27 compared to other groups (p=0.031). In addition, in terms of T21 and T18 risk groups, a significant relationship was observed with the mother’s serum PAPP-A level (p<0.001) (Table 2).
Evaluation of chromosomal abnormalities based on T18 and T21 risk group
The results of data analysis showed that chromosomal abnormalities, structural abnormalities, and fetal and maternal adverse obstetrics outcomes were more in the high-risk group for both T18 and T21 (p<0.001) and intermediate-risk group for both T18 and T21 (p<0.001) (Tables 3 and 4).

Table 1. Description of the characteristics of the studied population according to different variables

*HR: High Risk, IR: Intermediate Risk, LR: Low Risk.

Table 2. Evaluation of chromosomal abnormalities and outcomes based on maternal serum PAPP-A MoM levels

* HR: High Risk, IR: Intermediate Risk, LR: Low Risk.

Table 3. Evaluation of chromosomal abnormalities and outcomes based on T18

* HR: High Risk, IR: Intermediate Risk, LR: Low Risk.

Table 4. Evaluation of chromosomal abnormalities and outcomes based on T21

* HR: High Risk, IR: Intermediate Risk, LR: Low Risk.

Table 5. Evaluation of chromosomal abnormalities and outcomes based on fetal sex

* HR: High Risk, IR: Intermediate Risk, LR: Low Risk.

Evaluation of chromosomal abnormalities and outcomes based on fetal sex
The results indicate no significant relationship between fetal gender and chromosomal abnormalities, structural anomalies, maternal adverse outcomes, or total adverse outcomes (p>0.05). However, the rate of adverse fetal outcomes is significantly higher in female fetuses compared to male fetuses (p=0.035). The risk of screening for trisomy 18 is higher in male fetuses than in female fetuses within the high-risk and intermediate-risk groups (p<0.001). This increased risk for male fetuses is also observed in the screening for trisomy 21, but only within the high-risk group (Table 5) (p<0.001).

Evaluation of chromosomal abnormalities and outcomes based on ROC curve and area under the curve (AUC)
Establishing a specific cut-off point based solely on PAPP-A MoM levels for adverse pregnancy outcomes, such as structural abnormalities, adverse fetal outcomes, or adverse maternal outcomes, presents significant challenges when using the ROC curve. While the ROC curve is effective in identifying a cut-off point for chromosomal abnormalities, such as Down syndrome, it falls short of defining a single threshold for other pregnancy complications. This limitation highlights the complexity of predicting non-chromosomal adverse outcomes solely based on PAPP-A MoM levels. In the present analysis, the optimal cut-off point for identifying chromosomal abnormalities was determined to be 0.625, whereas for total adverse outcomes, the cut-off was established at 0.585. The Area Under the Curve (AUC) for chromosomal abnormalities was 77%, with a 95% confidence interval ranging from 74 to 79%. In contrast, the AUC for total adverse outcomes was 64%, with a 95% confidence interval ranging from 63 to 66% (p<0.001). Based on the AUC, it was 76.8% for chromosomal abnormalities, indicating that the determined cut-off has good accuracy. For total adverse outcomes, the figure was 64.4%, suggesting that the cut-off provides moderate accuracy (Figures 1 and 2).

Discussion
In the present study, the results showed that the decrease in PAPP-A level was associated with an increase in pregnancy outcomes as well as chromosomal abnormalities. In addition, the risk of T18 and T21 in born fetuses also increases. 
Movahedi et al showed that the frequency of term labor was higher in pregnant mothers who had normal PAPP-A levels. This was despite the fact that the decrease in PAPP-A level can be associated with pregnancy complications including preeclampsia and preterm labor and many other cases (11). In line with the present study, Scott et al showed that the decrease in PAPP-A serum level can be associated with the increase of genetic abnormalities and Down syndrome in patients. They also stated that the reduction of PAPP-A level may be accompanied by normal karyotype, however, the risk of genetic abnormalities in patients should be considered (12). In another study, it was shown that only 53% of patients whose PAPP-A levels were decreased had trisomy 21. Therefore, they concluded that reducing the level of PAPP-A in Alzheimer’s disease cannot increase the risk of trisomy 21 in all patients (13). In several other studies, it was found that the decrease in maternal PAPP-A level can be associated with an increase in the incidence of pregnancy outcomes and genetic disorders in newborns (14-16).
In general, it can be said that the reduction of maternal PAPP-A level can be associated with pregnancy outcomes in patients, however, in many conditions, it can be associated with normal karyotype. Therefore, to accurately diagnose high-risk patients exposed to genetic abnormalities, it is better to evaluate PAPP-A levels during pregnancy along with other biomarkers.
The present study showed that the incidence of adverse fetal outcomes is significantly higher in female fetuses compared to male fetuses. The risk of screening for trisomy 18 is higher in male fetuses than in female fetuses within the high-risk and intermediate-risk groups. This increased risk for male fetuses is also observed in the screening for trisomy 21, but only within the high-risk group.
In contrast to the present study, Neuman et al also showed that the incidence of pre-eclampsia in pregnant mothers with reduced PAPP-A levels whose babies were male was higher compared to females (17). In line with the present study, Cowans et al also showed that the incidence of trisomy 21 was higher in male infants who were accompanied by a decrease in maternal PAPP-A levels (18). In previous studies, it was also shown that the risk of T18 and T21 was higher in male fetus compared to female (19). The present study showed that the risk of T18 and T21 increases in babies with pregnancy outcomes and genetic abnormalities.
Specifically, based on evidence, it has been determined that chromosomal abnormalities can be one of the risk factors for genetic diseases (20). A decrease in PAPP-A levels in many patients can lead to a series of pregnancy consequences. These consequences, even though they can disrupt the development of the fetus, in some cases may lead to genetic and structural abnormalities. These abnormalities increase the risk of T18 and T21 in patients (21).
Finally, according to the present study, the optimal cut-off point for identifying chromosomal abnormalities was determined to be 0.625, whereas for total adverse outcomes, the cut-off was established at 0.585. Based on the AUC, it was 76.8% for chromosomal abnormalities, indicating that the determined cut-off has good accuracy. For the total adverse outcomes, the figure was 64.4%, suggesting that the cut-off provides moderate accuracy. In line with the present study, Kantomaa et al showed PAPP-A ≤0.40 MoM should be considered as a primary screening cut-off for adverse pregnancy outcomes as approximately 23% will develop either Small for Gestational Age (SGA), Hypertensive Disorder of Pregnancy (HDP) or Preterm Birth (PTB) (22).

Conclusion
In general, it can be said that the decrease in PAPP-A serum level in pregnant mothers can be associated with maternal and fetal adverse outcome. The occurrence of these complications can increase the risk of T18 and T21 in patients. Therefore, monitoring PAPP-A serum level during pregnancy can help in identifying high risk patients.

Ethical approval 
This article does not contain any studies with human participants or animals performed by any of the authors. All the procedures performed in the studies involving human participants were in accordance with ethical standards of Local Ethics Committee of Shahid Beheshti University of Medical Sciences (IR.IUMS.REC.1401.607), as well as 1964 Helsinki Declaration.

Conflict of Interest
The authors declare that they have no conflict of interest.