Pregnancy

Pregnancy occurs when a sperm penetrates an egg. The single sperm that burrows into the egg is the successful one out of millions contained in the man's semen. This is called fertilisation, and usually takes place in the woman's fallopian tube after the matured egg has been released from one of her ovaries (ovulation).

Sperm may contain an X chromosome or a Y chromosome. If an X fertilises the egg, the result will be a girl. If a Y penetrates the egg, the result will be a boy. Sperm and eggs each contain 23 chromosomes. The total number of chromosomes required to make a baby is 46, and this is achieved when a sperm and egg fuse at fertilisation.

The fertilised egg, known as an ovum, immediately begins to divide into a growing cluster of cells. Between five to seven days after ovulation, the fertilised egg implants itself into the wall of the womb (uterus) and produces root-like outgrowths called villi. These help to anchor it to the lining of the womb and will eventually grow into the placenta, the organ that feeds and protects the baby until birth.

The placenta maintains and nourishes the baby by enabling the transfer of oxygen, carbon dioxide, amino acids, fats, vitamins and minerals from the mother's blood. It also allows the transfer of waste substances from the baby.

Embryonic and foetal stages

From the time of implantation into the wall of the womb until approximately the eighth week of life, the developing baby is known as an embryo. Development is rapid during this stage, as specialised cells begin to form the vital organs, nervous system, bones, muscles and blood.

After the eighth week of pregnancy, the developing baby is called a foetus. It is about 2.4cm (1 inch) long, with most of the internal organs formed. External features, such as the eyes, nose, mouth and ears, can be seen, and fingers and toes start to appear.

As the unborn baby grows, so does the womb. A fluid-filled double membrane surrounds the baby. This normally breaks when the baby is ready to be born, releasing the amniotic fluid (the liquid that surrounds the baby).

During pregnancy the baby floats freely in the amniotic fluid, and constantly swallows this fluid, excreting it in their urine. Much information about the baby's health can be obtained during a procedure called amniocentesis, where a small sample of amniotic fluid is taken for testing.

The length of a normal pregnancy varies between about 37 and 42 weeks, although the delivery date is calculated at 40 weeks from the first day of your last period. Only around 5% of babies are born on their due date. Babies born before 37 weeks are considered premature (or pre-term).

The first trimester

Weeks 0 to 13 are known as the first trimester of pregnancy. The baby's development is greatest during this stage and by the end of week 13, it will be fully-formed. Some of the common discomforts of pregnancy, such as nausea, fatigue, and breast tenderness, will be most pronounced during these early weeks.

The second trimester

Weeks 14 to 26 make up the second trimester. During this time, the baby continues to grow and develop, and the mother starts to gain some weight, as extra fat is laid down as energy reserves. This is also the time when the baby's movements in the womb can be felt, and she, or he, may begin to develop patterns of activity.

The third trimester

The third trimester runs from week 27 to the birth of the baby. During this stage, the baby will start to lay down its own fat stores, going through rapid growth phases in preparation for birth.

The lungs will also mature, and senses such as hearing, taste and sight will develop. You may find it more difficult to get comfortable at night, with backache and you will need to urinate (pass water) more often. Practice contractions, known as Braxton Hicks, can be a regular feature during the third trimester.

Some signs and symptoms to look for if you believe you might be pregnant include

• missed period,
• nausea with or without vomiting,
• tiredness,
• dizziness,
• breast changes and breast tenderness, and
• frequent urination.

Feelings of sickness (nausea) affect the majority of women during pregnancy, particularly during the first three to four months. Tiredness may be more pronounced during the first and third trimesters.

If you suspect that you are pregnant, or have taken a home pregnancy test which confirms that you are pregnant, you should arrange to see your GP or midwife straight away.

This is to ensure that you receive all the necessary advice and support you need, as early as possible. Midwives may be based at your GP's surgery, a local hospital or midwife unit.

The diagnosis of pregnancy is mainly determined by testing for the pregnancy hormone, human chorionic gonadotropin (HCG). HCG can be detected in the woman's blood and urine even before the first missed period.

It is this hormone that is measured by home pregnancy tests. A high HCG level may indicate a multiple pregnancy, such as of twins or triplets, although the most reliable test is an abdominal, or transvaginal scan.

Abdominal or transvaginal scans may be used to confirm pregnancy, how many embryos are present, and to check that the embryo is located in the womb, rather than in the fallopian tube, as in the case of an ectopic pregnancy.

The care you receive from your GP, midwife, and other health professionals is known as antenatal care.

The purpose of antenatal care is to track the progress of your baby, and to monitor both yours and the baby's health.

If this is your first baby, you will probably be offered 10 antenatal appointments. If you have had children before, you will probably be offered seven appointments.

Your first antenatal appointment

Your first antenatal appointment should take place early in your pregnancy - within the first 12 weeks. Your GP or midwife will ask you about your health and discuss any health problems you might have had in order to see if you need any additional care or treatment.

They will also give you information about what other pregnancy care services are available, what maternity benefits you may be entitled to, and give you practical advice about diet and lifestyle.

Your weight may be measured and, if you are seriously under- or overweight, you may require additional care. Your blood pressure will also be taken, and your urine will be tested for the presence of protein, which can be a sign of kidney disease or diabetes.

Ultrasound scans

Ultrasound scans use sound waves to produce an image of your developing baby.

Early in your pregnancy (usually around 10 to 13 weeks) you should be offered an ultrasound scan to estimate when your baby is due, and to check whether or not you are expecting more than one baby.

If you see your midwife or GP for the first time when you are more than 13 weeks pregnant, they should offer you a scan then. Between 18 and 20 weeks, you should be offered another scan to check that your baby is developing normally.

Screening tests

You will also be offered a series of tests - screenings - to check for possible conditions that could affect the health of you or your baby. You do not have to agree to have any of these tests, but the information the tests can provide may help you receive the best possible care during your pregnancy.

Conditions that are routinely screened for during pregnancy are:

• anaemia,
• Down's syndrome
• hepatitis B,
• HIV,
• rubella, and
• syphilis.

Antenatal classes

Your midwife or GP will recommend that you attend antenatal classes and will be able to give you information about what classes are available. These classes can help you to prepare for the birth and give you the chance to meet other prospective parents.

NHS antenatal classes are free, and are normally held in a hospital or health centre, and are run by a midwife or other health professional.

You will normally attend a course of classes over six to eight weeks, during the last few months of your pregnancy. For some classes, you may be encouraged to bring a 'birthing partner' - somebody who will be able to support you during labour. Typically, this is the baby's father, but some women choose a close relative or friend instead.

Topics that are covered in antenatal classes include:

• what to expect during labour,
• information about pain relief and delivery options,
• exercises to keep to fit,
• preparing for life with a new baby,
• how to care for a newborn baby,
• relaxation techniques, and
• common emotions that are commonly felt by mothers during pregnancy, labour and after the birth.

Some NHS trusts also offer specific antenatal sessions for parents expecting more than one baby (twins or triplets), as your labour and delivery will need to be carefully managed. You should also expect to have extra antenatal appointments, often at a consultant-run clinic, for close monitoring of your health and that of your babies.

It is common for pregnant women to experience several of the following conditions:

• anaemia,
• constipation,
• haemorrhoids,
• heartburn,
• hypertension (high blood pressure),
• hypotension (low blood pressure),
• gum disease (gingivitis),
• genital infections, such as thrush (candida) and trichomoniasis,
• mood changes,
• nausea and vomiting, and
• urinary tract infections.

It is very important to attend all antenatal appointments with your midwife, GP or consultant. Conditions such as pre-eclampsia, which can be life-threatening, can be detected only through regular antenatal checks.

Nausea and vomiting in pregnancy

Nausea and vomiting in pregnancy is usually called morning sickness. However, in reality, morning sickness can occur throughout the day or night. While some women never get morning sickness at any time during their pregnancy, most experience at least some mild morning sickness. Nausea and vomiting is a normal part of pregnancy and the symptoms typically ease after around 16 weeks of pregnancy.

Ways to reduce the feelings of nausea and prevent vomiting include:

• Eat small, frequent meals that are high in carbohydrate and low in fat, such as whole grain bread, rice, cereal and pasta.
• Eat plain or ginger biscuits 20 minutes before getting up.
• Many women find the certain foods, or smells, can trigger the symptoms of morning sickness. Recognising these triggers can help you avoid them.
• Try to get plenty of rest because tiredness can make the nausea worse.

Miscarriage

Approximately one pregnancy in four ends in miscarriage, and most of these occur during the first 12 weeks of pregnancy. For many women, the first indication of miscarriage is vaginal bleeding or discharge, sometimes accompanied by abdominal pain or backache, rather like period pains.

Some women may notice that pregnancy symptoms, such as nausea or breast tenderness disappear. Vaginal bleeding in early pregnancy is called 'threatened miscarriage', but does not necessarily develop into a miscarriage. Many women will go on to have a normal pregnancy.

Ectopic pregnancy

Ectopic pregnancy occurs when the fertilised egg (ovum) becomes implanted at a site in the body other than in the womb lining. An ectopic pregnancy is a potentially fatal condition because it can cause severe internal bleeding. Early diagnosis and surgical treatment are therefore essential.

Symptoms of an ectopic pregnancy include a pain in your shoulder tip, vaginal bleeding (the blood will be more watery than your normal period, sometimes described as looking like prune juice), one-sided abdominal pain and pain when passing stools (faeces) or urine.

Pre-eclampsia

Pre-eclampsia is a condition that only occurs during pregnancy, or immediately after the delivery of the baby. Women develop high blood pressure (hypertension) together with protein in the urine and fluid retention (oedema). Symptoms include sudden swelling of your face, hands, feet and ankles, rapid weight gain, vision problems (blurring or flashing lights in front of your eyes), abdominal pain and headaches.

Pre-eclampsia develops in about one in 10 pregnancies, usually after the sixth month of pregnancy. Most cases are mild, develop towards the end of the pregnancy, and are easily treated. However, in a severe form it can be life-threatening for both mother and baby.

Placenta praevia

Placenta praevia occurs when the placenta covers part or all of the cervix (the baby's exit from the womb). It may cause bleeding in the pregnancy and, if the placenta does not move up as the pregnancy progresses, a caesarean birth will be necessary. In most women, the placenta moves out of the way before birth, but additional ultrasound scans may be required to monitor the situation.

Where an earlier placenta praevia has moved out of the way before birth, the risk of a vasa praevia must be eliminated. A vasa praevia occurs when one or more of the baby's placental or umbilical blood vessels cross the entrance to the cervix beneath the baby, and can be ruptured or compressed with the onset of labour. If this is diagnosed, a caesarean birth will be necessary.

Down's syndrome

Other tests during pregnancy can detect any chromosomal conditions, such as Down's syndrome. This occurs when one of the 23 pairs of chromosomes (inherited from each parent) has an extra chromosome attached, resulting in learning disabilities and sometimes health problems. Women at higher risk of carrying a baby with such conditions may opt for testing procedures like amniocentesis or chorionic villus sampling (CVS).

Obstetric cholestasis

Obstetric cholestasis is a rare complication that occurs during pregnancy and is caused by a build-up of bile (a naturally occurring chemical) in your bloodstream. The exact cause of obstetric cholestasis is not yet known, although some researchers suggest that it may be a result of a reaction to the hormone changes that occur in your body during pregnancy. The condition may also run in families.

Obstetric cholestasis is a rare condition that affects approximately 0.1-1.5% of pregnancies. However, it can cause serious complications, significantly increasing the risk of your baby being born prematurely.

Some babies also experience foetal distress. This is when your baby shows signs of being in trouble, such as a change in their heart rate, or their movement. In severe cases, a small number of babies (approximately 2%) are stillborn.

The main symptom of obstetric cholestasis is intensely itchy skin. The itching is normally worst on your:

• arms,
• legs,
• palms of your hands, and
• soles of your feet.

The itching also tends to be worse at night. Other symptoms of obstetric cholestatis include:

• difficulty sleeping,
• lethargy,
• lack of appetite,
• nausea, and
• jaundice (yellowing of the skin).

An estimated one in 5 women experience some itching during their pregnancy. However, for most women, it is a result of the stretching of their skin, as well as an increased blood supply to the skin. If your itching becomes particularly intense, or it is accompanied by any of the other symptoms above, you should contact your GP or midwife for advice.

If you are diagnosed with obstetric cholestasis, you and your baby will be carefully monitored. Medication can help to control the itching, and you may require an induced labour, or caseseran birth, to help ensure that your baby is not affected by the build-up of bile.

Molar pregnancy

Another rare complication is molar pregnancy. For every 500 babies born in England and Wales, there is around one molar pregnancy (0.2%).

In a molar pregnancy, when the sperm fertilises the egg, the fertilised cell cannot develop into an embryo, due to genetic abnormalities. However, the layer of cells (trophoblast cells) that would eventually become the placenta continues to develop. Sometimes called a hydatidiform mole, this growth of cells continues to produce the pregnancy hormone, hCG (human chorionic gonadotrophin), at an abnormally high level.

Most molar pregnancies are diagnosed quite early, perhaps as a result of bleeding, or following an ultrasound scan. If left untreated, molar pregnancies normally result in miscarriage.

If you have a hydatidiform mole, it can usually be treated in a small operation, which is carried out under general anaesthetic. After treatment, your level of hCG will probably be monitored. In most people, the level will fall. However, if it stays the same, or continues to rise, further treatment may be needed.

After a molar pregnancy, you may be advised to wait for 12 months before trying for another baby.

Stillbirth

If a baby is born after 24 weeks of pregnancy, and does not show any signs of life at any time after being born, it is known as a stillborn baby. Sometimes, the cause of death is clear. However, in many cases the cause of death cannot be established.

The stillbirth rate in the UK is 5.5 per 1,000 births (about 0.5%). There is a slightly higher risk for women under the age of 20 - 6.6 per 1,000 - (about 0.6%), and women aged over 40 - 7.2 per 1,000 - (about 0.7%).

Not smoking during pregnancy will reduce the risk of a stillbirth.

Many stillbirths are preceded by a reduction in the baby's movement. If you feel that your baby has 'gone quiet', contact your midwife or GP immediately.

A stillbirth can be a traumatic experience for parents. Many find that bereavement counselling helps them come to terms with their loss.

A stillborn baby must be cremated or buried. Many couples have found that holding a proper funeral for their baby helps in coping with the trauma of losing their child.

There are a number of things that you can do during your pregnancy to lower the risk of problems occurring, and help keep you and your baby healthy.

Exercise

Moderate exercise is recommended for most pregnant women. It helps boost energy levels, improves your overall health, and helps prepare you for labour by increasing your muscle strength and stamina.

Your midwife or GP will be able to recommend how much and what sort of exercise is good for you. Generally, 30 minutes of moderate daily exercise is recommended for pregnant women during most of their pregnancy. Activities like walking or swimming are ideal.

You should avoid contact sports, exercises that require you to lay flat on your back, and any extreme sports or activities that may put you at risk of falling over. Scuba diving is not recommended while pregnant because it can damage the baby's development.

Things to avoid

Some other things that you should avoid while pregnant that may put your baby's health at risk are outlined below.

• Smoking - smoking increases the chances of your baby being born under-weight or being born too early - both of which could harm their health. Your midwife, or GP, will be able to give you advice about quitting smoking, or you can call the NHS Pregnancy Smoking Helpline on 0800 169 0 169.
• Alcohol - the Department of Health recommends that you should not drink alcohol while you are pregnant because it can harm your baby. You should also avoid drinking alcohol if you are trying for a baby. If you do drink when you a pregnant, you should not drink more than one to two units of alcohol, once or twice a week (one unit is roughly a small glass of wine, half-pint of ordinary strength bitter or lager, or a pub measure of spirits).
• Cannabis - the effects of cannabis on unborn babies is unknown, so it is impossible to say what smoking cannabis could do to your baby.
• Prescription and over-the-counter medicines - only a few prescription and over-the-counter (OTC) medicines have been shown to be safe for pregnant women by good quality studies. Your GP will only prescribe you a prescription medication when it is felt that the benefit outweighs the risk. You should use as few OTC medicines as possible.
• Complementary therapies - very few complementary therapies have been proved to be safe and effective for pregnant women. You should not assume they are safe and use them as little as possible.
• Shark, swordfish and marlin - you should avoid eating these types of fish as they all contain high levels of mercury, and therefore could affect your baby's developing nervous system.

Diet

While you are pregnant, you should try to follow a healthy, balanced diet based around the four main food groups. For example:

• four to six daily portions of carbohydrates, such as rice, pasta, cereals, bread and potatoes,
• at least five daily portions of fruit and vegetables,
• three daily portions of protein from sources such as meat, poultry, fish, pulses and eggs, and
• at least one portion a day of pasteurised dairy products, such as milk, cheese and yoghurt.

Eating fish is very healthy for you, and your unborn baby. However, you should avoid eating shark, marlin and swordfish, as these fish contain high levels of mercury, which can affect your baby's development.

Also, limit the amount of tuna fish you eat to no more than two tuna steaks or four medium-sized cans per week.

You should drink plenty of fluids such as water and fruit juice, preferably at least two litres every day. This will help your body to get rid of toxins and waste products, and it can also help to prevent constipation and nausea.

You should limit the amount of caffeine you have, as too much caffeine can lead to your baby having a low birth weight, which can cause them health problems later on.

Caffeine

The Food Standards Agency recommends no more than 200mg of caffeine per day during pregnancy. This is equivalent to:

• two mugs of instant coffee,
• one mug of filter coffee,
• two mugs of tea,
• five cans of cola, or
• four (50g) bars plain chocolate (milk chocolate contains less caffeine than plain chocolate).

Some cold and flu remedies contain caffeine, so always check with your pharmacist before taking any.

Vitamins and supplements

Your GP or midwife should give you information about taking folic acid. This helps reduce the risk of your baby having conditions which are known as neural tube defects, such as spina bifida. The recommended dose is 400 micrograms a day from as soon as you think you may be pregnant (or ideally when you begin trying for a baby).

You should not take vitamin A supplements as they can cause abnormalities in unborn babies. Liver is high in vitamin A, so you should avoid that too.

Food hygiene

Your GP or midwife should give you information on how to avoid bacterial infections from food, such as listeriosis and salmonella, which could harm your baby. You should avoid:

• mould-ripened soft cheese, such as Camembert or Brie, and blue-veined cheese (there is no risk with hard cheese, such as Cheddar), or with cottage cheese or processed cheese,
• pâté, including vegetable pâté,
• uncooked or undercooked ready-prepared meals,
• raw or partially cooked eggs, or food that may contain them, such as mayonnaise, and
• raw or partially cooked meat, particularly poultry.

Toxoplasmosis is an infection that can occasionally cause problems for unborn babies. You can pick it up from undercooked or uncooked meat such as salami, which is cured, and from the faeces of infected cats or contaminated soil or water.

You should ensure that you:

• wash your hands thoroughly before handling food,
• wash all fruit and vegetables before eating them, including ready-prepared salad,
• thoroughly cook raw meat and ready-prepared chilled meals,
• wear gloves and wash hands thoroughly after gardening or handling soil, and
• avoid contact with cat faeces, either in cat litter or in soil.