PERINATAL OUTCOMES OF ADOLESCENT AND ADULT MOTHERS: A SYSTEMATIC REVIEW

: Objective: To identify and analyze studies published in the literature that researched adverse perinatal outcomes in live births to adolescent and adult mothers. Methods: The electronic databases PubMed and VHL (LILACS and MEDLINE) were consulted, using the MeSH descriptors with Boolean operators were used, which were grouped as follows: (“maternal age”) AND (“risk factors”) AND (“Pregnancy Complications OR “Adverse Birth Outcomes” OR “Perinatal outcome”). This analysis resulted in eight articles published between 2018 and 2022. Results: Studies presented a strong association between young maternal age (<20 years) and unfavorable neonatal outcomes, such as low birth weight, premature delivery, need for oxygen therapy and admission to the Neonatal Intensive Care Unit. No significant data were found on adverse outcomes in pregnancies in the optimum age range (20>35 years). Conclusion: The analyzed studies point to a strong association between young maternal age and some clinical-obstetric complications.


INTRODUCTION
Pregnancy is an important and complex phase for women, which is necessarily interconnected with integrated dimensions, such as physiology, neurobiology, epigenetics, mental health and socioeconomic and/or sociodemographic aspects. In this sense, it is important to highlight the range of knowledge that is involved in the function of increasingly describing and elucidating the gestational period (MALDONADO, 2017).
In general, the central objective of health research on this topic is to expand knowledge on the multiple factors that may contribute to a successful pregnancy and to identify risk factors that may be associated with unfavorable perinatal outcomes (DIAS et al., 2010;ANTONI e VARGAS, 2020).
It is estimated that around three hundred million women face pathological complications in the short and/or long term due to factors that directly interfere with pregnancy and childbirth, moments that are decisive in the well-being of the binomial. This rate is mainly related to the increase in the incidence of pregnancies at the extremes of the maternal reproductive age group, which corresponds to the age groups under 20 years and over 35 years of age, since these, in comparison with the 20-35-year age group, result in adverse outcomes for mothers and their babies (SANTOS et al., 2014).
In 2019, Brazil recorded 419,252 adolescent pregnancies (aged 10-19 years); 19,330 aged 10-14 years and 399,922 aged 15-19 years (FEBRASGO, 2021). Adverse outcomes of adolescent pregnancy are important public health problems with significant social impact. Socioeconomic and sociodemographic aspects need to be mentioned. Adolescent pregnancy, for example, is a phenomenon observed with overwhelming frequency in developing countries, especially in those marginalized places where there is also low level of education (BLUM; GATES, 2015;CECAGNO et al., 2020).
It is worth noting that maternal age may be associated with adverse outcomes for both mother and baby. Low birth weight, oxygen therapy, prematurity, neonatal sepsis, and admission to the intensive care unit are some of the complications observed in live births to women under the age of 20 years (GIBBS et al., 2022). Thus, the present study aimed to search and analyze studies published in the literature presenting adverse perinatal outcomes of live births to adolescent and adult mothers.

First Steps, Search Criteria and Selection of Studies
This is a systematic review of the literature, following the parameters established by the Cochrane Handbook for Systematic Reviews (COCHRANE, 2019). It is of the descriptive type since it is a study which proposes to research the features of a specific phenomenon and, from this, collect information which concerns certain characteristics, such as age distribution, gender prevalence and origin (GIL, 2010). For reporting the results, guidelines based on the PRISMA Checklist were followed. First, according to the initial research question, the PECO(s) search strategy was developed, which is described in Table 1. The search strategy was guided by the PECO(s) acronym, which replaces the letter I (Intervention) with the letter E (Exposure). were used, which were grouped as follows: ("maternal age") AND ("risk factors") AND ("Pregnancy Complications" OR "Adverse Birth Outcomes" OR "Perinatal outcome").

Inclusion Criteria
Those studies that 1) were published in article format; 2) research conducted with human beings; 3) published in Portuguese or English; 4) published between 2018 and 2022; 5) studies that discussed perinatal outcomes; 6) peer-reviewed publications; 7) observational or experimental studies that had as population: pregnant women aged less than 20 years and pregnant women aged 20>35 years met eligibility criteria.

Exclusion Criteria
Literature reviews; animal studies; publications not available as full text; repeated studies in databases; publications in book format, theses, and dissertations.
Furthermore, aiming to guarantee the homogeneity of the sample, it was also decided to discard studies that investigated perinatal outcomes from the effects of COVID-19 in adolescent and adult mothers; studies that focused on perinatal outcomes resulting from a sexually transmitted disease (STD), psychological condition and/or exposure to alcohol and other drugs.

Data and Risk of Bias Analysis
Studies were analyzed by title and abstract. Then, the remaining studies were read in full. Finally, the appraisal tool for cross-sectional studies (AXIS), a tool to assess the quality of evidence, by means of a questionnaire with twenty evaluative items; the studies needed to reach a minimum of sixteen (DOWNES et al., 2016). The papers were analyzed by two reviewers and, in the studies in which there were differences regarding eligibility, this was resolved through consensus between the researchers.
After all the steps had their data extracted and compiled using Excel Software (2019). To guarantee greater control over the quality of evidence and, consequently, to increase the degree of reliability of the studies assessed and included in the review.

RESULTS
Twenty-two studies were identified in the period between 2018 and 2022, but only eight were included, in view of the application of the AXIS protocol for the control of evidence. Of the eight articles, four were conducted in the Asian continent (India, Taiwan, China, and Nepal), two in the African continent (Tanzania and Zambia), one in Europe (Switzerland) and one in South America (Brazil). Figure 1 illustrates the screening and selection process for articles based on the PRISMA flow diagram model.   As shown, the articles were also analyzed using the AXIS protocol, which establishes a list of twenty criteria, such as ethical aspects, quality of the instruments used, clarity in reporting data and adequate population. The Table 3 shows data after this analysis and it characterizes the authors, year of publication, sample size, results, and limitations of the studies.

11,501
Adolescence did not present statistically significant associations with poor maternal health outcomes. However, the risk of obstructed labor, premature rupture of membranes and postpartum hemorrhage was higher among adolescents when compared to women aged 20 to 24 years, while the risk of serious infection was lower and not significant. Adolescents were also 1.36 times more likely to have a lowbirth-weight baby (95% CI 1.12, 1.66) and were at risk of preterm delivery (aOR = 1.40, 95% CI 1.06, 1.84). no formal education, while one in nine adult mothers had no formal education (32.6 vs. 14.2%, p < 0.001). Compared to adult mothers, adolescent mothers were more likely to experience prolonged labor (aOR-1.56, 95% CI, 1.17, 2.10, p=0.003), preterm delivery (aOR-1.40, 95% CI, 1.26-1.55, p < 0.001) and having a small-forgestational-age baby (aOR = 1.38, 95% CI 1.25, 1.52, p < 0.001). The chances of birth defects increased more than twofold in adolescent compared to adult mothers (aOR = 2.66, 95% CI 1.12, 6.33, p = 0.027). JIANG, et al., 2018 To To calculate the frequency and assess factors associated with low birth weight.

746
The proportion of low birth weight was 7.6% (mean birth weight of 3.2 kg) and, in the multiple analysis, the presence of twinning, the age range of the pregnant women (showing protection for low birth weight between ages ≥18 years and <35 years), and cesarean section were associated with low birth weight. Maternal age 20-35 years constituted risk for the primary outcome.
Small sample compared to the population base of hospital institutions. RAO, et al., 2018 To examine the secular trend of low birth weight and macrosomia in Foshan, a city located in southern China.

102,526
Maternal age 20-24 years (OR = Of the studies presented, three have a retrospective observational methodological design, three are documental, one is a population-based prospective cohort, and one is a case-control study. Heterogeneity was observed regarding publication journals, with recurrence of publication only in the journal BMC Pregnancy and Childbirth, where two studies were published. 2018 was identified as the year with the most publications (3), followed by 2020 and 2021 (2) and 2022 (1).

DISCUSSION
From the results, it was possible to observe that there was a considerable volume of publications that discussed adverse perinatal outcomes, taking maternal age as one of the independent variables. The studies focused on research questions involving the prev- To facilitate the explanation of the data found in the studies, some thematic categories were created based on the main common outcomes in the analyzed studies and with other variables, which are: Preterm birth; Low birth weight and Association between age and socioeconomic and sociodemographic factors.

Preterm Birth
Premature or preterm birth is defined as the one in which the baby is born early, more precisely before the 37 th week of gestation, and is responsible for perinatal morbidity and mortality rates in the world. The etiology of this type of delivery is heterogeneous, with uterine infection, preeclampsia and/or anemia being the main causes (MOHA-PATRA; SARAOGI; MISRA, 2022). It is worth mentioning that, depending on the gestational age at which the preterm birth occurs, the baby may suffer from a series of developmental complications, such as visual, auditory, and brain deficiencies (GIBBS et al., 2022).
The analyzed studies presented a strong association between young maternal age and the prevalence of preterm birth. The study by Younes et al., (2022) categorized preterm birth as extreme (<32 weeks), moderate (32<34 weeks) and late (34<37 weeks). For extreme preterm birth, from regression analysis, it was seen that advanced maternal age was strongly associated. Furthermore, chromosomal/congenital anomalies, preterm history and assisted pregnancy were also predictive variables in the univariate and multivariate analyses.
Young maternal age (aOR 2.76; 95% CI) was configured as a predictor in cases of moderate preterm birth, as well as having chronic hypertension, assisted pregnancy and male baby. Women of ideal and advanced age showed no significant association with the variables.
The study by Mohapatra, Saraogi and Misra (2022) presented a counterpoint to these results that confirm the initial hypothesis. The study surveyed a sample of 12,345 live births, of which 682 were premature births, demonstrating an incidence of premature birth in the population of 5.52%. On the other hand, adult maternal age showed higher frequency (n = 360, 64.98%) and young maternal age had a rate of n = 86 (15.52%), while advanced age had a frequency of 108 preterm births (19.49%).
In the other studies, adolescent mothers were 1.36 times more likely to have a baby with low birth weight (95% CI 1.12, 1.66) and were at risk for premature birth (aOR = 1.40, CI 95% 1.06, 1.84), from a sample of 11,501 women (TEMBO et al., 2020). Other researchers have also published results like these, reinforcing the greater probability of premature birth in adolescents (GURUNG et al., 2020;JIANG;MISHU;LU, 2018).

Low Birth Weight
The analyzed studies showed a higher prevalence rate of low birth weight in babies born to adolescent mothers. The incidence was 14.3% of adolescents against 6.3% of non-adolescent mothers, in a sample of 13,266 participants (MTONGWA; FESTO; ELISARA, 2021). In the study by Tembo et al., (2020) adolescents were 1.36 times more likely to have a baby with low birth weight, in addition to the risk of prematurity, as previously described.
In the study conducted in Brazil by Moreira;Sousa;Sarno (2018), low birth weight was recorded in 140 pregnant women, from a sample of 746 pregnant women, representing, therefore, 17.6%. On the other hand, women of ideal age represented 59.1% of the total sample. However, it is emphasized that the number of pregnant women evaluated may not correspond to a sampling of the studied population base.
In China pointed out the highest prevalence among pregnant women of maternal age was between 20 and 24 years and from 30 to 34 years, in a sample of 102,525 participants (RAO et al., 2018). It is important to emphasize, on the other hand, that the number of women under the age of 20 years was smaller in proportion, compared to other studies performed in underdeveloped countries. For these reasons, it is considered essential to also discuss the macrosocial factors involved in this problem in public health worldwide.

Association Between Age and Socioeconomic and Sociodemographic Factors
To broaden the contextual perspective on the multiple variables involved in the phenomenon of adolescent pregnancy, it was decided to mention some of the social determinants and conditions of health. One of them refers to socioeconomic factors, since, as shown in other studies, adolescent pregnancy occurs more frequently in developing countries, with elevated levels of poverty and low educational levels (DIAS; ANTONI e VARGAS, 2020).
Some of the studies analyzed in this review point in this direction, which demonstrate a higher prevalence of pregnant adolescents from lower economic strata, with a lower level of educational instruction (MOHAPATRA; SARAOGI; MISRA, 2022;GURUNG et al., 2020).

CONCLUSION
The purpose of our study was to identify and analyze studies published in the literature that researched adverse perinatal outcomes of live births to adolescent and adult mothers, to assess whether maternal age could be considered an independent predictor variable for unfavorable outcomes in live births.
From the data presented in most studies, there is a strong association between young maternal age and some clinical-obstetric complications, such as preterm birth, low birth weight, growth retardation, oxygen therapy, malformations, and macrosomia.
It should be noted that this review has some methodological limitations, such as the number of databases studied, language restriction to Portuguese and English, and statistical analysis. Thus, it is suggested that more research be performed with the aim of expanding on this theme, in view of its importance for the scenario of outcomes and results of live births to adolescent and adult mothers.