Primary sex characteristics are those directly related to the sex organs . In males, the first stages of puberty involve growth of the testes and scrotum, followed by growth of the penis.  At the time that the penis develops, the seminal vesicles , the prostate , and the bulbourethral gland also enlarge and develop. The first ejaculation of seminal fluid generally occurs about one year after the beginning of accelerated penis growth, although this is often determined culturally rather than biologically, since for many boys first ejaculation occurs as a result of masturbation.  Boys are generally fertile before they have an adult appearance. 
Rates of teenage pregnancies are higher in societies where it is traditional for girls to marry young and where they are encouraged to bear children as soon as they are able. For example, in some sub-Saharan African countries, early pregnancy is often seen as a blessing because it is proof of the young woman's fertility.  Countries where teenage marriages are common experience higher levels of teenage pregnancies. In the Indian subcontinent, early marriage and pregnancy is more common in traditional rural communities than in cities.  The lack of education on safe sex, whether it is from parents, schools, or otherwise, is a cause of teenage pregnancy. Many teenagers are not taught about methods of birth control and how to deal with peers who pressure them into having sex before they are ready. Many pregnant teenagers do not have any cognition of the central facts of sexuality.