What happens to your body during pregnancy?

Pregnancy is a period of considerable changes in a woman´s body. These changes, affecting virtually every part of the body, are all geared towards growing and delivering a healthy baby, without harming the mother.

Changes begin within days of conception when the fertilised egg implants itself in the wall of the uterus. The first changes are subtle, and most women will not notice them. However, some women claim that they were aware of their pregnancies within hours of conception.

Pregnancy lasts an average of 266 days (38 weeks) from the date of conception, or 40 weeks from the first day of the last menstrual period. Pregnancy is divided into three periods of three months each. These periods are known as the first, second and third trimesters. Each trimester brings with its own unique set of experiences.

The first trimester

In the first trimester, you may experience breast tenderness and swelling as the first signs of your pregnancy. This is caused by increasing levels of the hormones oestrogen and progesterone. About ten days after conception, the placenta begins producing the hormones oestrogen and human chorionic gonadotrophin, which help to maintain the pregnancy. The increase in the levels of these hormones commonly causes nausea and vomiting, widely known as morning sickness.

Early in pregnancy, many women also experience extreme tiredness, irritability, bloating, reflux, indigestion, dizziness and headache. You may also feel the need to urinate more often.

Nature may step in to protect the developing foetus from harmful substances by suddenly making you averse to smoking, drinking alcohol or eating particular foods.

These early symptoms, along with missed menstrual periods, will alert you to the fact that you may be pregnant. It is important to confirm a pregnancy as soon as possible, to allow your doctor to check for any risk factor that could endanger you or your baby. Pregnancy tests (using blood or urine) can detect whether you are pregnant by determining the hormone levels present in your body. Other changes such as softening of the cervix and uterus and engorgement of the vagina and cervix with blood, causing them to become bluish to purple, will help to confirm the pregnancy. Ultrasound scanning will detect the enlarged uterus at about six weeks, and the foetus's heart can be seen beating (on ultrasound scan) in most pregnancies by about eight weeks.

Your first physical examination during pregnancy is likely to be very thorough, to detect any possible risk factors and allow for proper monitoring of your pregnancy. Your weight, height, and blood pressure are measured. Your neck, thyroid gland, breasts, abdomen, arms, and legs are examined; your heart and lungs are checked with a stethoscope; and the backs of your eyes examined with an ophthalmoscope. The doctor wil also perform a pelvic and a rectal examination, noting the size and position of the uterus and any abnormalities of the pelvis. Determining the pelvic bone dimensions helps the doctor anticipate how easily the baby will pass through at delivery.

Good nutrition and avoiding harmful substances are especially important during this early phase of preagnancy. Your doctor is likely to recommend a pre-natal vitamin supplement, containing folic acid and iron, to ensure that you get all the nutrients you need.

The second trimester

The second trimester is generally regarded as the best phase of a pregnancy. The morning sickness and tiredness have usually cleared up by week 12 and your growing belly is not yet too large to make you feel uncomfortable. However, you may find that hormonal changes make you more emotional and prone to bouts of forgetfulness. You may also suffer from water retention.

By the start of the second trimester (at 12 weeks), the uterus extends beyond the pelvis into the abdomen and can usually be felt when the lower abdomen is examined. However, your pregnancy may not be obvious to casual observers for some weeks to come.

The baby's heartbeat can be heard early in the second trimester, with the use of a Doppler ultrasound instrument. By about the 16th week, you may begin to feel the first flutters of movement from the baby. By about 20 weeks, your uterus will extend above the belly button, and an ultrasound scan can identify the gender of your baby. Between weeks 24 to 28, your baby is at his or her most active. More sensitive to the environment, your baby can respond to touch and will jump in reaction to a loud noise.

The amount of blood pumped by your heart every minute (your cardiac output) increases by up to 50 per cent during pregnancy. This increase peaks at around 24 weeks. Like the heart, the kidneys work harder throughout pregnancy, filtering an increasing volume of blood. The activity of the kidneys normally increases when a person lies down and decreases on standing up. This difference is amplified during pregnancy, which is one reason why you may feel the need to urinate frequently while trying to sleep.

During the second trimester, you may also start experiencing occasional tightening of the uterus. These contractions, called Braxton Hicks contractions, are normal and harmless.

The increases in maternal oestrogen and progesterone may make pregnant women more susceptible to dental problems, so it is important to go for regular dental check-ups. It is probably best to delay any dental x-rays until after the birth, though. On a positive note, most women find that the hormonal changes result in stronger nails, radiant skin and shiny hair from this phase of pregnancy onwards.

The third trimester

The third trimester is regarded as the home stretch. During this time, the excitement of being pregnant is starting to wear off, the discomfort of a large belly is becoming annoying, and most mothers are eager to give birth and finally meet their babies. Your weight will continue to increase during the third trimester, sometimes to alarming levels. Weight gains of between 10 and 15 kg are quite normal during pregnancy, with low weight gain regarded as a warning sign of poor foetal growth.

Your enlarging uterus extends to the level of the navel by 20 weeks and to the lower edge of the rib cage by 36 weeks. The space taken up by the enlarging uterus and the increased production of the hormone progesterone cause your lungs to function differently. A pregnant woman breathes faster and more deeply because more oxygen is needed for herself and the foetus and you are likely to become increasingly out of breath after exertion. The lining of the respiratory tract also receives more blood during pregnancy, which can cause a stuffy nose and temporary changes in the sound of your voice. Hormonal changes may make you very emotional, irritable and prone to excessive perspiration during this trimester.

As your pregnancy progresses, pressure from the enlarging uterus on the rectum and the lower part of the intestine may cause constipation. This is worsened by high levels of the hormone progesterone present during pregnancy. Constipation may lead to another common problem during pregnancy, uncomfortable haemorrhoids (piles). Eat plenty of fibre-rich foods and drink lots of fresh water to avoid these problems. Heartburn and burping are also common.

Late in pregnancy, the increase in kidney activity is even greater when a pregnant woman lies on her side rather than her back. Lying on your side relieves the pressure that the enlarged uterus puts on veins carrying blood from the legs and thus improves blood flow, increasing kidney activity and cardiac output.

Swelling (oedema) is common, especially in the legs. Varicose veins in the legs and the area around the vaginal opening (vulva) are also common in the third trimester. Ease the discomfort by wearing loose clothing around the waist and legs, wearing elastic support hose or resting frequently with your legs up. Pica, a craving for strange foods or non-foods, such as starch or clay, may develop.

You may develop pigmentation changes in your skin during this phase of pregnancy. A common complaint is mask of pregnancy (melasma), a blotchy, brownish pigment that may appear on the skin of the forehead and cheeks. Pigmentation may also increase in the skin surrounding the nipples, and a dark line commonly appears down the middle of the abdomen from the navel to the pubic bone.

Small, spider like blood vessels (spider angiomas) may appear in the skin, usually above the waist, as may thin-walled, dilated capillaries, especially in the lower legs.

As your body prepares itself for birth, a hormone called relaxin begins to soften the hip joints. This may result in a change in your stride, and you may find yourself waddling. The weight of your uterus may also cause you to adopt a swaybacked posture late in pregnancy, which can cause backache.

Report any worrying symptoms to your doctor. Symptoms that may need immediate attention include:

  • Chronic headaches or dizziness
  • Persistent nausea and vomiting
  • Visual disturbances
  • Vaginal bleeding or discharge
  • Pain or cramps in the lower abdomen
  • Severe swelling of the hands or feet
Getting back to normal

Some changes that occur during pregnancy may take months to revert to normal. You may find that pigmentation changes, loss of abdominal muscle tone and weight gain last for some years after birth. Interestingly, you may even find that the hormones that soften your cartilage to allow for easier deliver have left your hips slightly wider and your feet a size bigger. If you have concerns about the way in which your body has changed, ask your doctor for advice on exercise and diet plans to help you bounce back faster.