This was a cross-sectional study with an analytical focus. It took place from March 1st to April 30th, 2018.

The study population consisted of students from Maurice Delafosse High School and Grand Yoff Middle School.

Inclusion criteria

Included in the study were students aged 13 to 18 years.

Criteria for non-inclusion

Adolescents who did not wish to participate in the study.

The sample size was calculated on the basis of the proportion of adolescents aged 15 and 18 using contraception, which is 24.7% according to the 2017 DHS [2] using the simple random sampling method. Two schools (a high school and a middle school) were randomly selected using the ALEA function of Microsoft Excel 2018 software. This draw was made on the basis of the list of schools provided by the Dakar Academy Inspectorate. In each school, a captive audience approach was used in the classrooms to identify students who volunteered to participate in the study [7] . Only those who had verbally expressed their consent had received the questionnaire.

Four hundred and fifty-two (452) students participated in the survey. Participants, from the first to the last year of high school, were qualified to participate in the study.

The questionnaire had been developed by the co-authors. It had been tested in a randomly selected high school. The pre-test involved 40 students. A workshop to correct and validate the questionnaire had been organized by the co-authors. The questionnaire was divided into 3 parts. The first part concerned the description of the respondent and his or her social environment. The second part concerned the sexual behavior of students. The last part concerned knowledge and practices in the field of modern contraception.

These were self-administered questionnaires administered by students. The questionnaire was given to the students by the interviewers. After giving the students filling instructions, they gave them 45 minutes to complete the questionnaires. After the time allowed, the questionnaires were retrieved by the interviewers.

The data entry was done with the Epi-info version 7 software. The analysis was done with SPSS version 21 software.

The description of the student population was based on their socio-demographic characteristics, their living environment and their access to family planning services.

The analysis had identified factors associated with current use of modern contraceptive methods among students. This use is defined as the use of contraceptive methods in sexual relations between the student and his or her partner (either directly if the student is a girl or indirectly by the partner if the student is a boy).

Dependent variable

In this study, we considered the use of modern contraceptive methods as a dependent variable, which is dichotomous: use (yes = 1) and non-use (No = 0). By modern contraceptive method, we considered the following methods: condom, pill, injectables (depo-provera), implant, intrauterine device (IUD), emergency contraception.

Independent variables

The explanatory variables were socio-demographic characteristics, their living environment and access to family planning services including information services. Chi² and Fisher exact to the 5% risk threshold had been used for the comparison of proportions. The difference was considered significant when p < 0.05.

The multivariate analysis examined factors associated with contraceptive use among students. To consider confounding and interaction factors, all variables with p-values less than 0.25 were included in the logistic regression model.

Four hundred and fifty-two (452) students were surveyed.

The average age was 16.3 years with a standard deviation of 1.5 and extremes of 13 to 19 years.

Girls were in the majority (62%) (see Table 1). The sex ratio was 0.61.

Distribution of students by sexual activity

Seventy-three percent (72.72%) of students who had sex had done so at an age below 16 years with a minimum age of 7 years (see Table 2).

Distribution of students according to contraceptive use

The question about the use of modern contraception was answered by 294 students. Current contraceptive use was reported in 26 students (8.84%). The method used was reported in 22 cases. Among the latter 20 students (90.9%) used condoms and 2 (9.1%) used the pill (see Table 3).

Thirty-five percent of the students did not answer the question.

Reasons for not using contraceptive methods

One hundred and seventy-four (174) students responded regarding the question, why you do not use a contraceptive method.

52.3% say they do not have sex, 38.5% prefer to keep their virginity until the age of marriage and 26.4% of students associated sex with matrimoniality (see Table 4).

Use of modern contraceptive methods according to family and social environment

Seven percent (7%) of the students undergoing family control used modern contraceptive methods (see Table 5).

Twelve percent (11.9%) of students who belonged to social groups used modern contraceptive methods (see Table 5).

Use of modern contraceptive methods based on knowledge of modern contraceptive methods

Twenty-nine percent (29%) of students who knew that youth hostels were a means of accessing contraceptives used contraceptive methods (see Table 6).

Age, gender, education level, access to a youth socio-educational home and having a child were the factors associated with the use of modern contraceptive methods among students (see Table 7).

In our study, the average age was 16.3 years with a standard deviation of 1.5 and extremes of 13 to 19 years. In Africa, studies had shown similar results with average ages of modern contraceptive use among young people aged 17 on average [8] . In 2002, the World Health Organization (WHO) studied the sexual trends of 15-year-old students in 35 countries. The study indicated that the average age of first sexual intercourse in most countries was 16 - 19 years for girls and 17 - 19 years for boys [9] . This may explain the onset of the need for contraception at these ages.

In our study, the students were mainly under 18 years of age (71.7%). The majority of adolescents (98%) were not on contraception; only 2% used a contraceptive method. Age was statistically significant for the use of modern contraceptive methods. Adolescents over 18 years of age were 4.7 times more likely to use a contraceptive method than others (AR = 4.7, 95% CI [1.02 - 22.5]).

In our study, girls accounted for 62.1% of the sample. The majority of girls (98.4%) were not on contraception, only 22.1% of boys used a modern contraceptive method. In 2002, the World Health Organization (WHO) studied the sexual trends of 15-year-old students in 35 countries. The study showed that the percentage of boys having sex was often higher than that of girls [9] .

In Senegal, another study had shown, as ours did, that men were more involved in modern contraceptive practice than women [10] . Indeed, more of them used the male condom but also emergency contraception for their sexual partner. In this study, boys were 28 times more likely to use a contraceptive method than girls (AR = 27.8; 95% CI: 6.8 - 100). These results are similar to those found in Ethiopia, where boys were more likely to have sex (65%) than girls [8] .

Elsewhere, in other contexts in Europe, it has been noted that young women are more likely to use modern contraceptive methods than those in less developed countries such as those in sub-Saharan Africa [11] .

However, in other countries such as Thailand, a study has highlighted the emergence of a new form of sexuality for young girls in schools who tend to take responsibility for their sexual activity by deciding for themselves [12] . The gender difference in contraceptive use and sexual involvement is explained in some studies by socio-cultural and religious considerations [13] . Senegal is still a country subject to strong religious and traditional influences. Thus, Senegalese social norms lead Senegalese women to be reluctant to declare that they are concerned about sexuality and aspects related to contraception or sexual protection [14] .

The students were between 13 and 18 years old (average 16.3 years). 68.9% of the students were in the first cycle and 31.1% in the second cycle. Twenty-three (20.7%) of the respondents had heard of at least one contraceptive method. There was a statistically significant relationship between education level and use of modern contraceptive methods (p < 0.05). The male condom was the method most known by the students. Few students (14.9%) were familiar with modern methods. Contraceptive use was more frequent among second cycle students (20.7%) than among first cycle students (1.7%).

A study in Niger showed that contraceptive use was more frequent among first-cycle students (64.5%) than among second-cycle students (35.5%) (p < 0.05) [15] . Unlike in Tunisia, women’s educational level was significantly associated with contraceptive use. This finding could be explained by the fact that educated women were better informed about different contraceptive methods [16] .

According to the Demographic and Continuous Health Survey in 2014, modern or traditional contraceptive prevalence increases sharply with education level. For modern methods, prevalence increases from 14% among women with no education to 29% among those with primary education and 33% among women with medium/secondary education or higher [17] .

The impact of knowledge acquisition on the use of contraceptive methods has been proven by numerous studies [18] . In middle and high schools in Dakar, few students have any knowledge of contraceptive methods (12.6%). There is also a lack of knowledge among students of how to access modern contraceptive methods.

However, students who know that youth hostels in schools are a place where contraceptive methods can be obtained are 3.9 times more likely to use contraceptive methods AR = 3.9, 95% CI [1.1 - 14.9]. Youth hostels are socio-educational hostels in middle and high schools in Senegal with, among other roles, a role of peer education and the provision of contraceptive methods.

This result reflects the importance of introducing sexual health interventions for students in schools. Studies had shown similar results and highlighted the importance of sexual health interventions in schools [19] . In a study conducted in 25 African countries, it was pointed out that facilitating access to contraceptive methods in schools has an impact on reducing unwanted pregnancies [20] . Studies have shown that young people’s sexuality is better addressed by health policies when sex outside marriage is recognized, accepted and regulated rather than prohibited in all contexts outside marriage [21] .

Youth hostels in schools with their permissive character contribute to the democratization of young people’s sexual choices.

It is widely accepted that modern contraception has reduced teenage pregnancies [22] . However, the question addressed by this study is whether the occurrence of pregnancy in a teenager may lead him or her to use contraceptive methods for future sexual intercourse. In schools in Dakar, the study showed a statistically significant link between having a child and the use of modern contraceptive methods (AR = 25.6, 95% CI [2.2 - 100.0]). Students who had a child were 25.6% more likely to use a contraceptive method. This attitude could be explained by the implementation of strategies to avoid further unwanted pregnancies by adolescents. Indeed, unwanted pregnancies can have disastrous consequences for teenage girls and their families [23] . Contraceptive use is part of strategies to avoid pregnancy [24] .