Introduction

The World Health Organization defines adolescence as the biological phase between childhood and adulthood, from 10 to 19 years of age. It is a transitional period of development characterized by rapid physical, cognitive, and psychosocial growth. In addition, the initiation of sexual activity often occurs during this stage of life, which can lead to unintended consequences such as unplanned pregnancy or sexually transmitted infections (STIs).¹

Teenage pregnancy is associated with several adverse outcomes for both the pregnant adolescent and her infant. It also has a negative impact on the adolescent's development into adulthood, affecting physical and mental health as well as educational attainment.² Pregnancy prevention programs, including comprehensive sex education and promotion of consistent and accurate use of effective contraceptive methods, must be accessible to all adolescents, particularly those with predisposing factors for teenage pregnancy.³

Recognizing the negative and long-term consequences of teenage pregnancy and birth is critical to effectively addressing this issue. Although the teenage birth rate in Portugal has declined since the 1970s, it remains an important health problem that requires a consistent and multidisciplinary approach.

Objectives

The aim of this study was to analyze the incidence of teenage pregnancy in Portugal and globally, addressing risk factors, impact, and preventive measures.

Development

According to the United Nations International Children's Emergency Fund (UNICEF), an estimated 15% of young women worldwide gave birth before the age of 18 in the period 2015-2020.⁴ The incidence of teenage pregnancy varies widely by country, regions within countries, urban versus rural setting, and socioeconomic factors such as women’s income level and educational attainment. The World Population Prospects from 2021, published by the United Nations Department of Economic and Social Affairs, highlights a global decline in adolescent birth rates since 2000-2005, with rates dropping by nearly 20%  from 53 to 44 births per 1,000 girls aged 15-19 years worldwide. Nonetheless, the highest incidence of pregnancy before the age of 18 was reported in Western and Central Africa, where 27.3% of women aged 20-24 years gave birth before age 18. Conversely, regions such as Western Europe/Eastern Europe and Central Asia/North America reported some of the lowest adolescent birth rates, with 8, 17, and 21 births per 1,000 girls aged 15-19 years, respectively.⁴

In terms of reducing adolescent pregnancy, South Asia, North America, and Western Europe were able to reduce their rates by more than 60% between 2000 and 2005. In contrast, the reduction rate in sub-Saharan Africa over the same period was about 15%.⁴ More progress is needed in these regions to ensure that the burden of early childbearing is reduced.

In Portugal, data from the last 60 years show a significant decline in the fertility index among girls aged 15-19. In 1976, the fertility index peaked at 51.1 births per 1,000 young girls, the highest recorded in the last six decades. Following global trends, Portugal reached its lowest recorded fertility index in 2020, with a rate of 6.7‰.⁵ This decline in pregnancies among adolescent girls is consistent with global trends observed over the last 30 years, which show a significant decrease in fertility indices and birth rates in the general population.⁶ The downward trend may be partially attributed to improvements in education levels, older age at marriage, increased investment in and dissemination of sexual education, greater availability and awareness of contraceptive methods, improved knowledge of the risks associated with sexually transmitted diseases, and easier access to abortion services.⁷

Teenage pregnancy is closely related to adolescent sexual behavior. In a study by Gaspar de Matos on the health of Portuguese adolescents with 6,997 adolescents with a median of 14 years, most adolescents surveyed had never had sexual intercourse. ^(8,9 The author found a decrease from 23.7% who had already started their sexual life in 2002 to 11.5% in 2018. The majority (63.2%) of adolescents who had already started their sexual life did so after the age of 14 years or more.⁹ Of particular note is the fact that the percentage of adolescents who reported using a condom during their last sexual act decreased from 70.4% in 2014 to 66% in 2018, which was accompanied by a slight increase in the use of oral contraceptive methods (from 31% to 33.9%).^9,10 Girls were more likely than boys to report using a condom at their first sexual intercourse (79.4% vs. 65.9%). Older adolescents were also more likely to report condom use during their first sexual experience.¹⁰ Alarmingly, 17.1% of adolescents who were already sexually active reported a link between sexual intercourse and alcohol or drug use.⁹ Notably, the study also concluded that while the much feared "early" sexual intercourse during adolescence has stabilized, the associated risks - such as HIV infection, other STIs, and unplanned pregnancy - have increased.⁹

In 2010, a similar study concluded that while there were some positive trends in the sexual behavior of Portuguese adolescents, significant gaps remained in their knowledge of sexual and reproductive health. The study highlighted personal ineffectiveness in areas such as communicating and negotiating condom use, as well as embarrassment in obtaining and carrying condoms. In addition, respondents displayed increasingly liberal attitudes toward sexual activity and more frequently asserted their right to engage in sexual relations.¹¹

Several factors appear to be associated with an increased risk of teenage pregnancy, and it is not uncommon to observe an interrelationship among them.¹² It has been shown that older adolescents are more likely to become pregnant than younger counterparts. However, younger teenagers tend to have more unintended pregnancies.¹³ Education plays a crucial role in preventing teenage pregnancy. Low levels of education, extended periods of school absence, and poor educational results are positively correlated with adolescent pregnancy.¹⁴ In addition, the relationship between economic factors and adolescent pregnancy cannot be ignored, as poor economic status is associated with a higher risk of teenage pregnancy. As noted above, most high-income countries have low rates of adolescent pregnancy.^2,15 Adolescents with mental health disorders, including depression and low self-esteem, have an increased risk of pregnancy compared with their healthy peers.^14,15 In some countries, the lack of accessible health centers or hospitals deprives adolescents of information about pregnancy risks and contraceptive methods, which may contribute to a higher likelihood of pregnancy.¹² Several reports have linked behavioral factors such as risky sexual behavior, use of alcohol, tobacco, or drugs, and sexual or physical abuse to teenage pregnancy.^16,17 The family environment plays a key role in the development of children and adolescents, and its association with teenage pregnancy has been studied extensively. Some authors suggest that adolescents who live without their parents or with a family member who experienced pregnancy before adulthood, such as their mother or sister, may be more susceptible to becoming pregnant during adolescence.^16-18)

Adolescent pregnancy is also often associated with adverse social, physical, and psychological outcomes for both the pregnant adolescent and her children. Worldwide, complications of pregnancy and childbirth are the leading cause of mortality among adolescent women.² Prevention of unintended pregnancy, as well as counseling and monitoring by an experienced multidisciplinary team, appears to have a positive impact on reducing the comorbidities associated with this problem.¹⁹ The majority of adolescent pregnancies are unplanned, and once diagnosed, adolescents should be informed about the potential risks and consequences of pregnancy at this stage of life and made aware of the options available, including legal termination of pregnancy.²⁰⁾

The risk of adverse maternal and fetal outcomes, including preterm delivery, preeclampsia, anemia, intrauterine growth restriction, preterm premature rupture of membranes, low birth weight, and perinatal death appears to be increased in teenage pregnancy.^2,21-26 Sociodemographic factors such as low economic status, poor education, unmarried status, or biological immaturity have been suggested to contribute to these adverse outcomes.^2,22 However, the association between teenage pregnancy and adverse outcomes has yielded inconsistent results across studies, possibly due to varying definitions of adolescence, small sample sizes, and inadequate control for confounding variables.

In a retrospective study comparing maternal and fetal outcomes between pregnant adolescents and pregnant adults (20-34 years), Kirbas et al. reported that the adolescent group had a significantly higher risk of preterm delivery and preeclampsia. In addition, the neonates of adolescent mothers were found to have an increased likelihood of low birth weight and low Apgar scores.²⁵ A multicenter study in 29 countries involving 124,446 pregnant women aged ≤24 years evaluated the adverse effects of pregnancy in adolescents and young adults. ⁽² The study found a statistically significant increase in the risk of preterm delivery, eclampsia, puerperal endometritis, and systemic infections in pregnant adolescents. Poor perinatal outcomes, such as low birth weight and severe neonatal morbidity, were observed in the children of pregnant adolescents. In addition, a significantly higher proportion of severe anemia (hemoglobin <7 g/dL) was observed in the adolescent group. Notably, inadequate prenatal care among some participants may account for some of these findings, as previous research has shown that appropriate obstetric monitoring and maternal health behaviors reduce the risk of pregnancy complications among adolescents and their offspring. It is noteworthy that with optimal medical care, maternal mortality in adolescents is not significantly increased compared to pregnant women aged 20-24 years.^19,27 Marvin-Dowle et al. also examined the relationship between maternal age and pregnancy outcomes, with a focus on adolescent pregnancies, and found that children of pregnant adolescents had an increased risk of prematurity and low birth weight. However, in this study, maternal outcomes in pregnant adolescents were favorable, with a lower risk of gestational diabetes, instrumental delivery, or cesarean section compared with adult mothers.²⁶⁾

The current literature review shows that complications associated with adolescent pregnancy are predominantly linked to the newborn, with preterm birth and low birth weight being major concerns. Factors such as nutritional deficiencies and smoking, which are more prevalent in this adolescent population, may significantly contribute to adverse outcomes.²⁸ Furthermore, gynecological immaturity, characterized by short cervical length, reduced uterine volume, and increased susceptibility to subclinical infections, may also contribute to complications. Another study showed that adequate obstetric surveillance significantly reduced the risk of adverse neonatal outcomes. Specifically, the likelihood of low birth weight and prematurity decreased when pregnant adolescents attended six or more prenatal visits during pregnancy.^29,30 However, pregnant adolescents tend to initiate obstetric surveillance later, exhibit poor prenatal health behaviors, and attend fewer medical appointments, which may explain the association between adolescent pregnancy and adverse birth outcomes.^31,32

Several publications have investigated the psychosocial impact of teenage pregnancy. A systematic review concluded that the prevalence of psychiatric pathology in postpartum adolescents was approximately 32.5%, with a predominance of anxiety disorders. Moreover, rates of postpartum depression were higher in adolescents than in young adults. Given that depressive symptoms are an independent risk factor for subsequent adolescent pregnancy, prompt management and treatment of depression is critical.³³ Compared to their peers, adolescent mothers are at greater risk for lower academic achievement, lower income, poor family support, and relationship conflict. As a result, children of adolescent mothers are more likely to be born into poverty, suffer from health and cognitive disorders, have poor educational outcomes, and become adolescent parents themselves.^15,34 Living in the same environment as a sibling who gave birth during adolescence increases the likelihood of teen pregnancy.^16,18 Wall-Wieler et al. reported that the relationship between an older sister’s teenage childbearing and a younger sister’s adolescent pregnancy is stronger than the relationship between a mother’s teenage childbearing and a younger daughter’s adolescent pregnancy.³⁵ Family and social support may be the cornerstone to reducing the adverse socioeconomic outcomes associated with adolescent pregnancy and parenting.³⁶⁾

As discussed above, teenage pregnancy is a multifactorial condition that requires an evidence-based approach. It should be addressed not only by intervening with young people at risk, but also by recognizing that families and communities play a key role in prevention. There are two main types of prevention programs, depending on their primary goal. Primary prevention programs aim to reduce the incidence of teenage pregnancy, while secondary prevention programs aim to mitigate the effects that teenage pregnancy can have on the development of the teenager and the child once pregnancy has occurred.³⁷

The United States (US), in particular, has focused on abstinence-only programs to address the problem of teenage pregnancy between 1996 and 2009. In 2005, a systematic review was conducted to compare abstinence-only secondary school-based pregnancy prevention programs with abstinence-plus programs in terms of their effects on teenage sexual behavior, contraceptive knowledge, contraceptive use, and pregnancy rates. This review, which included sixteen randomized controlled trials with a total of 29,599 participants, concluded that although the variability and small number of studies precluded a definitive conclusion about which type of program is most effective, the majority of abstinence-plus programs increased rates of contraceptive use, with one study showing effects that lasted at least 30 months.³

Since 2009, there has been a paradigm shift in U.S. teen pregnancy prevention policy toward an evidence-based approach, including several programs directed at educating teenagers about both abstinence and contraception to prevent teen pregnancy. In addition, several teen pregnancy prevention programs aim to prevent second or subsequent teen births. The most successful of these programs recognizes that preventing second births often requires a different approach than preventing first births.¹³ This policy shift came after a growing consensus that success in teen pregnancy prevention does not necessarily have to be an "either/or" proposition that pits "abstinence-only education" programs (sometimes referred to as sexual risk avoidance programs) against "comprehensive sex education" programs (sometimes referred to as sexual risk reduction programs).³⁸

One of the key factors in preventing teenage pregnancy is addressing risky sexual behaviors, which can be mitigated through age-appropriate sex education tailored to young people’s developmental stages. In Portugal, Decree-Law 259/2000 reinforces the right to reproductive health and establishes conditions for the promotion of sex education and access to health services related to sexuality and family planning for young people. This law emphasizes the important role of schools in providing sexual education and recognizes school teachers as key promoters of sexual health and education. It also mandates the availability of health appointments in primary healthcare facilities, with free distribution of contraceptives to teenagers.³⁹ Since 2007, following the legalization of voluntary termination of pregnancy (VTP) within the first 10 weeks of gestation, adolescents have been able to choose this option, with the need for parental consent when requested by pregnant adolescents under 16 years of age. According to the 2018 report on VTP in Portugal, 9.58% of all voluntary abortions were performed on teenagers, distributed as follows: 0.3% among adolescents under 15 years of age and 9.28% among adolescents between 15 and 19 years of age. In contrast, teenagers accounted for 2.52% of all live births in the same year. According to the latest report of the Division of Child and Adolescent Sexual Reproductive Health from 2023, the risk of VTP in Portugal is 50% for girls under 15 years of age and 40.3% for those aged 15-19 years.⁴⁰

Teenage pregnancy is usually reported from the perspective of young women. However, it is important to remember that in a significant proportion of cases, the male progenitor is also a teenager and, if he acknowledges paternity, may share some of the psychological, social, and economic burden.^41,42 Prevention efforts should recognize the role that young men's views and attitudes play in preventing pregnancy. Healthcare providers can help mitigate the problem of teenage pregnancy, especially by routinely discussing contraception and STI prevention with young men.

All contraceptive methods are considered suitable for healthy adolescents. However, the use of long-acting reversible contraceptives (LARCs) should be particularly encouraged in this age group, as the CHOICE study demonstrated that LARCs not only significantly reduce the incidence of unplanned teenage pregnancies, but also have a high continuation rate at 12 months  82% in nulliparous women and 86% in parous women under the age of 20. These rates are higher than those for combined hormonal contraceptives and comparable to those observed in adult women.^43-45) Otherwise, emergency contraception (EC) methods allow for the prevention of pregnancy after unprotected or inadequately protected sexual intercourse (UPSI). All women are eligible to use EC, including adolescents.⁴³ In Portugal, no medical prescription is required to purchase oral EC at pharmacies. Oral EC options include ulipristal acetate, a selective progesterone receptor modulator taken as a single 30 mg dose that remains effective for up to 120 hours after UPSI, and levonorgestrel, a progestin-based option taken as a single 1.5 mg dose that remains effective for up to 72 hours after UPSI. In addition, EC includes the option of inserting a copper intrauterine device (IUD), which must be placed by a trained healthcare provider. The copper IUD not only serves as an EC, but also provides effective contraception for up to 10 years. It is important to note that all EC methods are more effective the sooner they are used after UPSI.⁴³ Following the use of EC, healthcare providers should have a discussion with the teenager about available contraceptive methods and their efficacy and correct use.

Conclusions

Adolescent pregnancy is often associated with adverse social, physical, and psychological outcomes for both the pregnant adolescent and her children. Although the number of live births from adolescent mothers has decreased in Portugal in recent decades, it is important to recognize that pregnancies that end in voluntary abortion also have a significant impact on the lives of adolescent girls, although they are often not included in statistics. Promoting good sexual education, maintaining a stable economic status, ensuring easy access to health centers and specialized gynecological and obstetric care, avoiding sexual risk behaviors, and refraining from alcohol, tobacco, and drug use are crucial protective measures against teenage pregnancy. Mental health care is also of paramount importance and should be improved and promoted. In addition, condom use needs to be increased in this age group and sexual attitudes should be discussed in sexuality education programs, with a focus on effective communication and negotiation of sexual relationships using condoms. Adolescents should be informed about other contraceptive methods available and, where clinically appropriate, encouraged to use long-acting reversible contraceptives. Emphasis should also be placed on sexual education for young men, as they may also suffer the long-term consequences of unintended pregnancy and the impact on this subgroup has been much less studied.

Ultimately, adolescent pregnancy is a public health issue, and efforts should be made to engage all stakeholders, including adolescent boys and girls, their families, and the communities to which they belong.

Authorship

Ana Andrade - Literature Review; Writing - original draft

Luís Ferreira de Castro - Literature Review; Writing - original draft

Rosa Zulmira Macedo - Literature Review; Interpretation; Critical review of the article