Antenatal classes are a series of sessions, held in an informal setting, where expectant mothers and often their partners can gain information about all aspects of pregnancy, childbirth and parenting.

The classes are held by a midwife or childbirth educator, and are attended by women with similar due dates. They are not compulsory and are usually run by childbirth groups, although there are some available via the NHS. There is usually a small fee for joining a series of classes.

Subjects covered are usually dictated by what the members of the group particularly wish to learn about. This include signs of labour; positions for labour; coping with labour; pain relief options; breastfeeding; and general care of a newborn, including bathing, nappy changing and managing illness.

Q: I have just got a new job and it is the job of my dreams. It pays extremely well, offers flexible working and is pretty much on my doorstep. The only problem is I have to go away on business for four days every month. I feel consumed with guilt and am scared I am going to upset my 20-month-old son by not being there. My husband has a 9-5 job and will be with our son every evening after nursery and every morning when he wakes up. Am I just being silly?

A: It is totally understandable for you to be worried about leaving your son, even if he is in the care of his father and safe and sound at home.

Leaving your child for any length of time can be very difficult, but keep in mind your reasons for doing so. Money does not grow on trees and if this time away has to be a part of an otherwise perfect job, there is nothing to feel guilty about.

With regard to upsetting your little boy, you will probably need to brace yourself for some tears (yours and his) when you leave for your business trip, but your days away will soon become a part of your son's routine.

At 20 months, he understands more than you may realise, so make sure you take the time to sit down with him and explain that Mummy is going on a very important trip for a few days, but Daddy will always be here to look after him. Make sure you tell him how much you will miss him, but you won't be away for long and will soon be back safe and sound.

An X-ray is a method of photographing the structures of the body through the use of electromagnetic radiation.

Its safety during pregnancy depends on the type of X-ray that is necessary as different X-rays generate different levels of radiation. However, most medical and dental X-rays are acknowledged as safe as they do not expose the woman or the baby to dangerously high levels of radiation.

The levels of radiation of measured in rads, the unit that determines how much radiation has been absorbed by the human body. It is believed that a baby exposed to 10 rads of radiation may have an increased risk of learning disabilities and eye problems. However, most X-rays contain a much lower rad count, and it is unusual for an X-ray to contain more than five rads.

Water retention, or oedema, is a very common side effect of pregnancy and is an accumulation of fluid caused by sluggish circulation.

Fluid accumulates when the blood vessels near to the skin expand. This causes an increased blood flow, which in turn encourages fluid to move into the tissues and remain there.

It is most common in the second and third trimesters, but can be experienced at any point during pregnancy. It is usually worse during the hot summer months.

Vernix, also known as vernix caseosa, is a creamy white coating that develops on the unborn baby's skin at around 20 weeks of pregnancy. It is believed to act as a moisturiser, and protects the baby's skin while it is in the womb.

Towards the end of pregnancy, the vernix covering the baby begins to lessen. Therefore, most full term babies are born with little or no trace of the substance, although it is common for premature babies to have a coating of vernix.

Vernix is primarily composed of sebum, which is secreted from the foetus's glands. As well as protecting the skin, vernix is believed to hold antibacterial properties, which may help to guard against infection.

Ultrasound is a scanning technique used during pregnancy to examine the progress of the growing foetus, as well as the condition of the uterus, placenta and amniotic fluid.

It works through the use of high frequency soundwaves, which are sent through the uterus. These soundwaves bounce off the baby and echo. The echo transmits as an image, which details the location, movement and position of the baby.

The biggest echoes are created by the hardest tissues, such as bones. These echoes generate a white image, while the smaller echoes from softer tissues produce grey images. Fluid, such as amniotic fluid, will show as black as the echo will travel through, rather than bounce off.

Goodbye nappies, farewell dummy! Hello to potties and 'please' and 'thank you'. Your baby isn't a baby anymore, time for the ParentDish toddler masterclass...

Trisomy is the term given to describe an abnormal number of chromosomes within the cells that form an individual.

The human body normally contains 46 chromosomes per cell, which group into 23 pairs. When trisomy occurs, the individual carries an extra chromosome in one of these pairs, making a total of 47 chromosomes.

Because the extra chromosome can join any of the pairs, there are different types of trisomy, each of which will generate a defect within the individual. The severity of the defect will depend on the type of trisomy.

A special care baby unit (SCBU) is a specialist ward that a baby will be admitted onto if it requires medical help after birth. It may also be known as a neonatal unit (NNU).

Babies placed on SCBU will require care that is less intensive than the treatment provided in a Neonatal Intensive Care Unit (NICU). Therefore, some babies may enter SCBU after receiving treatment in NICU, or may be admitted straight to SCBU if their condition from birth has been less critical.

The SCBU unit is staffed by specialised paediatricians and paediatric nurses. The equipment on SCBU includes incubators, ventilators and a range of machinery that will monitor vital signs such as heart and breathing activity.

Towards the end of pregnancy, the baby will normally descend and dip into the woman's pelvic cavity, which is a process known as engagement. The baby will normally descend head-first, although it can be bottom or feet-first if the baby is in the breech position.

In the normal head-first position, relation to the brim is the terminology used to describe how much of the baby's head can still be felt resting above the pelvic cavity. This in turn reveals how much, if any, of the baby's head is engaged.

To make this assessment, the baby's head is divided into fifths. The lower the number, the lower the baby is. For example, a baby that is 5/5 has not yet descended into the pelvis and is resting above the pelvic cavity. A baby described as 4/5 (four fifths) has the top part of its head in the pelvis.