From the moment you conceive, your body begins to make adjustments to nourish and nurture your growing baby. While some of these changes can be discerned, others are subtler and may not be noticeable right away.

Around the time of your first missed period early pregnancy symptoms usually start to occur. You may notice tenderness in your breasts, fatigue and feelings of nausea. These, and other changes that you may experience during pregnancy (see page 67), can be an irritation and may even cause you some discomfort, but in many cases they can be relieved. However, any unusual discomfort or pain should never be ignored.


Pregnancy is a time of great hormonal activity. Production of existing hormones is raised dramatically and new hormones are made specifically for pregnancy.


This hormone, released by the developing placenta as it begins to implant within the uterus, is widely known as the ‘pregnancy hormone’, because it’s the one that is tested for in pregnancy tests. HCG is very important, because it triggers other hormonal activity needed to maintain your pregnancy and prevent menstruation from occurring. However, hCG does have some noticeable effects; in particular, it’s thought to be partly responsible for the nausea and vomiting – morning sickness – that occurs in the first trimester.


This hormone is present in nonpregnant women, but at much lower levels. Produced first by the ovaries, and then by the placenta at around 8 to 9 weeks, progesterone plays an important role in sustaining your pregnancy, including preventing the uterus from contracting strongly and endangering your unborn baby. Some women who conceive after assisted conception techniques, such as IVF or GIFT, are put on progesterone supplements, in the form of pills, suppositories, vaginal gel or injections.

After a scan you may be offered a photograph that you can share with others, which will help to make your baby seem real.

Progesterone maintains the functions of the placenta, strengthens the pelvic walls in preparation for labour and relaxes certain ligaments and muscles in your body. This relaxant effect can cause some unwelcome side effects.

Progesterone makes your bowel muscles sluggish, leading sometimes to constipation as well as a feeling of ‘fullness’ after eating. Progesterone also relaxes the sphincter (ring of muscle) between the oesophagus and the stomach, at times causing heartburn. It also causes veins to dilate, which can lead to varicose veins.

Another key role of progesterone is that of preparing your breasts for milk production. The hormone helps to stimulate and develop the duct system in your breasts, so that by the second trimester there is milk available. Early on you may feel its effects as breast tenderness.


This is another hormone present in high levels during pregnancy. Very early on, oestrogen helps to prepare the lining of the uterus for the pregnancy, increasing the number of blood vessels and glands present within the uterus. Oestrogen also is responsible for some increase in blood volume, which can lead occasionally to bleeding gums or nosebleeds. Its most noticeable effect is an increased flushing, or redness of the skin, resulting in the familiar ‘glow’ of pregnancy.


Besides hCG, progesterone and oestrogen, a number of other hormones have specific roles to play throughout pregnancy:

Human chorionic somatomammotropin (HCS) Also called human placental lactogen (HPL), this hormone is regulated by oestrogen and is produced within the placenta in large amounts. It plays a part in the development of your baby and helps your breasts to develop the glands needed for breastfeeding. It also mobilizes fat for energy and may promote the growth of your baby.


PRE-ECLAMPSIA Increased levels of progesterone can lead to blurred vision and headaches in pregnancy. However, if you develop these symptoms persistently in late pregnancy, tell your healthcare provider immediately; they could indicate pre-eclampsia, which can lead to eclampsia, a life-threatening condition (see page 254).

Calcitonin This conserves calcium and increases vitamin D synthesis, which enables your calcium and bone strength to remain stable despite an increased need for calcium for your baby.

Thyroxine (T4 and T3) This hormone is needed for the development of your baby’s central nervous system. It also increases your oxygen consumption, and helps your baby to process proteins and carbohydrates. Moreover, it interacts with growth hormones to regulate and stimulate your baby’s growth.

Relaxin This encourages your cervix, pelvic muscles and ligaments and joints to relax, in preparation for birth.

Insulin This helps your baby to store food in his body and regulates glucose levels. If you are diabetic and your condition is not well controlled, your baby can grow too much and have problems balancing his own glucose levels.

Oxytocin This hormone works in a kind of positive feedback loop. Released in response to the stretching of your cervix during labour it, in turn, causes your uterus to contract further. Similarly, oxytocin is released in response to stimulation of your nipples during breastfeeding and causes your milk to flow in the let-down reflex (see page 297).

Erythropoietin Produced in the kidneys, this hormone increases the total red blood cell mass and plasma volume by retaining salt and water.

Cortisol This helps your baby to use various foods properly within his body.

Prolactin This hormone helps to prepare your breasts for breastfeeding and promotes the growth of your baby.


Shortly after conception, profound changes begin to occur in your body’s circulatory system. One of the most significant of these is that your blood volume increases during pregnancy so that by week 30 you’ll have 50 per cent more blood circulating within your bloodstream. This massive increase is necessary for your body to provide an adequate blood supply to your developing baby, your enlarging uterus and the growing placenta.

Despite this increase in blood volume, some women’s blood counts decrease during pregnancy. This is because a blood count is a reading of the proportion of blood cells in relation to the amount of plasma – the fluid in which the blood cells are suspended – and the plasma tends to increase in volume more than the number of blood cells. Such a condition is called ‘dilutional anaemia’. Anaemia can also be caused by iron deficiency, in which case your healthcare provider may recommend that you take an iron supplement.

You also may notice that your heartbeat is a little faster. This is perfectly normal and an indication that your body is adapting to pregnancy. No one knows for certain why a woman’s heart rate increases during pregnancy. One theory is that it’s nature’s way of making sure that the extra blood volume gets circulated throughout the body.


Another change to your circulation, and one that you might notice, is a difference in your blood pressure. Some pregnant women’s blood pressure begins to fall in the first trimester, reaching its lowest levels midway through pregnancy. A sudden drop in blood pressure – for example, when you stand up quickly – can give you a feeling of dizziness, or you might even faint. This is nothing to worry about, but you should mention it to your healthcare provider.

Although it is usually symptomless, some women experience an increase in blood pressure. Your healthcare provider might pick this up at a routine check-up, and it is a condition that he or she will want to watch closely (see page 253).


You may find that you become short of breath toward the end of pregnancy. This is because your growing baby prevents your lungs from fully expanding. If you get short of breath, sit down and breathe steadily, consciously pushing your lungs up and down. If, however, you suddenly develop severe shortness of breath or get a sudden chest pain, seek medical attention at once.


If you feel hungry all the time, or especially late at night, you’ll be glad to know that there really is a physiological reason for this. During pregnancy your growing baby extracts glucose and other nutritional substances from your bloodstream throughout the day and night. So, in between your own meals, or at bedtime, your own blood sugar levels may well drop, leaving you feeling hungry. If you find yourself constantly foraging for food, try eating frequent, small healthy snacks, instead of fewer, large meals.