Puberty, Pregnancy and Sex

Growing up and making babies – puberty

Puberty is the name given to the physical and emotional changes which take place in most boys and girls between the ages of 10 and 14. Puberty occurs so that one day the boy or girl will be able to make a baby.

Reproduction, the technical term for making babies, can only occur when a boy and girl are sexually mature. One of the main physical changes of puberty is the growth and development of the sex organs – the parts of the body that are used to have sex and make babies. Sex organs that can be seen on the outside of the body are called ‘genitals’ while those that are inside the body are usually called ‘reproductive organs’.

Some more about a girl’s sex organs

Between a girl’s legs there are three small holes. At the front is the urethral opening which a girl urinates through, and at the back is the anus which she defecates from. In between these two holes is a third hole, her vaginal opening. From the vaginal opening there is a small passageway or tube, called the vagina, which leads to the reproductive organs inside the body.

When a girl has her period the blood comes out through her vagina. Inside the vagina there is a small piece of thin skin called the hymen. The hymen partly covers the vaginal opening, but there is still enough of a gap for blood to get through. Sometimes the hymen breaks and bleeds slightly when a girl has sex for the first time.

Some other important parts of a girl’s sex organs are:

  • The clitoris, which is at the front of a girl’s outside sex organs and is about the size of a pea.
  • The outer lips (labia) of a girl’s sex organs

The labia, the clitoris and the vaginal opening are together known as the vulva.

Some more about a boy’s sex organs

The boy’s sex organs outside his body are his penis and testicles (testes).

A boy’s penis hangs down between his legs at the front of his body. The main parts of a penis are:

  • The shaft – the main, long part of the penis.
  • The glans – the tip or head of the penis.
  • The foreskin – skin which covers the glans.

The foreskin can usually be pulled back quite easily. If it is tight it can be stretched by gently pulling it over the glans. All boys are born with a foreskin, but some have it removed when they are a baby, or later in life. The removal of the foreskin is called circumcision.

Underneath the penis is the scrotum – a loose, wrinkly pouch of skin that hangs down behind a boy’s penis. It contains his testicles. As a boy goes through puberty his testicles move lower down his scrotum. One of the testicles usually hangs lower than the other.

Eggs and Sperm

Inside a girl’s body are two small organs called the ovaries. Contained in these ovaries are hundreds of tiny sex cells called eggs, each no bigger than the head of a pin. At some point during puberty, the ovaries will begin to release these eggs. Usually one egg is released every month. This process is called ovulation.

A boy’s sex cells are called sperm and they are even smaller than a girl’s eggs. At puberty a boy’s testicles will start making sperm. Sperm leaves a boy’s body through his penis when it is hard and erect. This is known as ejaculation and it happens when a boy reaches the height of sexual excitement and has an orgasm. When a boy ejaculates, millions of tiny sperm are sent from his testes, up through his penis and out through the end. The sperm are contained in a sticky white fluid called semen.

When a boy’s sperm meets with a girl’s egg they usually join together, and a baby will begin to grow.

How do egg and sperm meet? – Sexual intercourse

The most common way that sperm get inside a girl’s body is through sexual intercourse. Sexual intercourse is when a boy puts his hard penis inside a girl’s vagina. It is also often called having sex or making love.

Having sex (which usually involves moving the penis in and out of the vagina) is usually very pleasurable for both a boy and a girl, and it will often result in an orgasm for one or both partners. If a boy ejaculates while his penis is inside the girl’s vagina (or if semen gets inside the vagina any other way) then the millions of tiny sperm in the semen will swim up the vagina, through the cervix (the entrance to the uterus) and into the uterus (also known as the womb). From there they will swim into the fallopian tubes. In one of the fallopian tubes the sperm may find an egg that has recently been released by the ovary. The sperm will surround this egg and try to get inside it. Eventually just one sperm cell will succeed, and the egg and sperm will join. This joining is also known as fertilisation or conception.

This joined sperm and egg then travel back down to the uterus, where they will settle in the thick, blood-rich lining and start to grow into a baby. It is at this point that we say a girl is pregnant.

What happens if the sperm and the egg don’t meet? – Periods


On average, the whole menstrual cycle (from the first day of the period to the day before the next) will last 28 days.

Girls generally only release an egg once a month, and it will normally take a few days to travel down the fallopian tube. If sperm don’t meet with the egg during this time, then she won’t become pregnant.

Without a new baby to nourish, the thick lining of the uterus is no longer needed. So, approximately 14 days after a girl’s egg is released, the bloody lining of the uterus will begin to come away, and will flow down through the cervix and out of the vagina. This process is called menstruation, and this is the blood that a girl will notice when she has her period. During puberty, a girl’s first period is a sign that she has released her very first egg, and is now able to have children.

Periods will usually last somewhere between 3 and 10 days. Around 14 days after the start of her last period, a girl will ovulate (release an egg) again, and will once again have the chance to become pregnant. This process of period, then ovulation, then period, is known as the menstrual cycle. On average, the whole menstrual cycle (from the first day of the period to the day before the next) will last 28 days, although variations between 21 and 35 days are quite normal.

More about pregnancy

Though an egg is usually released about the same time each month, this doesn’t mean that a girl can predict exactly when she will (or won’t) become pregnant. This is because girls usually have no way of knowing exactly when they are ovulating. Not only can the day of ovulation vary from girl to girl, it can vary from month to month in an individual girl.

In addition, sperm can survive for several days within the body, so they can ‘hang around’ waiting for an egg to be released if there isn’t one there already.

All this means that if a girl wants to avoid pregnancy but still have sex, she and her partner will need to use contraception. Some contraceptives, like the contraceptive pill, are used by girls. Boys can use condoms. Condoms also prevent sexually transmitted diseases from being passed from an infected person to another person during sexual intercourse.

Using contraception every time you have sex is very important if you want to avoid pregnancy. It is also important to remember that a girl can become pregnant even if:

  • It is the first time she has sexual intercourse.
  • She has sex before she has her first period (it could be that she is ovulating for the first time).
  • She has sex during her period (sperm can stay alive for several days).
  • A boy withdraws his penis before he ejaculates (pre-come, the fluid that leaks out the penis before a boy ejaculates, can sometimes contain sperm).
  • She has sex stan
    ding up (sperm can swim in any direction – up or down!).

Because periods stop during pregnancy, the first sign that a girl may be pregnant is usually a missing period. If a girl doesn’t start her period at the usual time, it is probably a good idea for her to talk to her doctor or another adult as soon as she can. Periods can come late for other reasons (for example when a girl is stressed, on a very strict diet or has been unwell), but if she has had sex in the past month, then it may be a good idea to take a pregnancy test to be sure.

Sexual feelings during puberty

It isn’t just the body that changes during puberty – our feelings can change too, and like the changes to the sexual organs, these feelings prepare us to have sex and make babies.

What are the main physical signs of sexual feelings?

The main sign for boys that they are getting sexually excited is when they get erections.

The main sign for girls is when their vagina begins to get moist. The clitoris gets bigger too.

For both boys and girls when they are sexually excited or “turned on”, extra blood comes to the surface of the skin, particularly around the penis and vagina. You can feel warm and sensitive and sexy just about anywhere on your body.

At what age do boys and girls start to get sexual feelings?

A person can have sexual feelings any time in their life, but these change around puberty. You might find some sexual feelings just seem to happen to you. But sexual feelings mostly come about from things you choose to do, either on your own or with someone else.

A main way that people express their sexual feelings is by touching their own genitals. This is called masturbation. Some people don’t masturbate at all, or hardly ever. Other people masturbate every day.


Masturbation is a normal and natural activity and is not bad for you unless you masturbate so much that you make your genital area sore.

Some girls enjoy touching their clitoris. Many boys enjoy touching their penis, particularly the tip.

When a person is masturbating they become more and more sexually excited. They may then reach a peak of sexual excitement which is called having an orgasm or “coming”. This is when all the tension and excitement that has built up is suddenly released. Boys ejaculate when they have an orgasm and their penis will then go limp. Everybody has their own way of masturbating that feels good for them. For many masturbation is their first sexual experience.

Masturbation is a normal and natural activity and is not bad for you unless you masturbate so much that you make your genital area sore. Masturbation does not stunt your growth, damage your health or cause you to become physically or mentally weak. If it did, the vast majority of people in the world would be very short and unhealthy!

Sexual feelings in relationships

When people have sexual feelings for each other they will usually want to do sexual things together. There is no set time or order in which to do things.

They often want to kiss and cuddle and hold hands. When people kiss they sometimes ‘French kiss’. This is when both people open their mouths when they are kissing and their tongues touch together.

People also like to touch each other through their clothes or put their hands inside to stroke or touch each other’s genitals.

There are a variety of other sexual activities that people will also do including sexual intercourse.

It can seem natural to bring sexual feelings into a relationship. But it can also change how people feel about each other and about themselves. You might want to do something because you feel curious about it. Or because you think it will make you feel good. And you might want to do it because you feel very close to someone.

But it’s important not to do any of these things because you feel under pressure. And it’s important to think about the consequences and how you’ll feel afterwards.