From their book ‘You and Your New Baby’ by Christine and Peter Hill.

It is not quite as easy as it might seem to make straightforward points about antenatal classes. At one level they are obviously a good thing, yet what one course offers is quite likely to be different from another. If you are in the fortunate position of being able to choose which ones to go to (which probably only applies to people living in cities or large towns) then it pays to think about what they can do for you. Then, by asking around, you can find out what goes on and choose accordingly.
Hospital classes are generally sound, though sometimes unexciting, and have the advantage of familiarising you with names, faces and the building where it’s ultimately all going to happen.
The main point of antenatal classes is to educate people so that they are not frightened during labour. They will also explain how to recognise the onset of labour; when to go into hospital; what is going to happen there; the language used by health professionals to describe the processes involved in childbirth; how to manage contractions; what forms of pain relief are available; and how to help the midwives deliver your baby. Whatever else the classes do, they must cover this ground.
Some classes go further. The better ones provide a framework for understanding the process of birth in terms of the female anatomy and physiology. They will also explain when and why medical interventions may be necessary. The best take the whole process beyond the birth (which of course is not the finale) and discuss current feeding techniques and basic baby care as well as the potential problems that are likely to arise when caring for a new baby.

Classes which are exercise-based are an extension of the above and not a substitute for them. They are not strictly necessary but a number of mothers enjoy them. Check that the class leader has herself been on a specific course on the supervision of exercises during pregnancy. The ligaments which stabilise joints become looser during pregnancy. This coupled with stretched abdominal muscles which are less able to stabilise the lower spine, means that pregnant women need careful supervision during exercise classes to ensure that they do not strain their back or damage (rather than strengthen!) their abdominal muscles. It is not quite so much that there are certain exercises to avoid, but that exercise during pregnancy needs to be supervised by an expert.
There are classes that concentrate solely on preparation for ‘natural’ childbirth or on idiosyncratic techniques for giving birth. These ultimately hinge upon you having a short, straightforward labour – something which is difficult to predict with certainty, particularly because it depends largely on the position of your baby just before birth and the shape of your pelvic bones. With this in mind, beware of classes which take an ideological stance, which insist that it is best to deliver in a particular position or place, and which oppose all forms of pain control or are anti-midwife or anti-obstetrician. Be very wary of classes that assume you can choose the kind of labour you will have. Left to nature the vast majority of women (87 per cent) will have a labour that does not require medical intervention.

This is the ‘natural’ birth that can make those fortunate enough to experience it feel proud that they have done it all on their own without medical intervention. The difficulty is that, particularly when it is you first baby, no one, not even your doctor or midwife, can be absolutely sure that you will have a natural birth until the very last minute.
It is not something that you, or anyone else, can make happen with any certainty because it hinges upon your baby and your pelvis. You may at the start of your pregnancy, be determined to have a natural birth. The chances are that you will but in fact the choice is not yours - there is nothing you or your classes can do to ensure it. If anything it is your baby’s choice and even he can’t have it all his own way if your pelvis is a difficult size or shape for his purposes.
Nor does it matter as far as your baby is concerned. Apart from the very few babies who have been snatched from the jaws of death, babies born with medical help are ultimately no different from those who were born ‘naturally. Some mothers are understandably, though inappropriately, concerned that in order to give their babies a ‘perfect start’ they have to have a ‘natural’ birth. Honestly, there is no factual basis for this.
Thus if you happen to fall into the 13 per cent who can’t have a baby without medical help, you may feel you have in some way failed, especially if you have been to the type of class which leads you to anticipate a brief, uncomplicated birth or which implies that it is up to you. Actually, labour isn’t one of those things that you can pass or fail.

No amount of special diets, exercises or breathing practice will ultimately affect the shape of your pelvis or the position of your baby at the onset of labour. Having a rigid idea of how you are going to have your baby, whether as an idea in your head or as a written birth plan, is risky because at the end of the day nature may not necessarily let you have your own way, even if the hospital backs your ideas to begin with. You can be prepared but you cannot control.
Good classes recognise that it is in your interests to have realistic expectations, which means you will be prepared for a range of eventualities.
Although there are some sets of classes that are primarily for couples, there is no firm principle that states that these are ‘better’. Dragging unwilling fathers-to-be along to them can be disruptive for the whole group and the sort of detail which many women welcome is not necessarily appealing to men. Some men are riveted by the whole process of pregnancy and birth, some are not. In the long run, either sort of man can be a totally competent husband and father.
Good courses will have a fathers’ evening but to go beyond this is a matter of personal choice, not an inevitable improvement.
One of the most remarkable things about parents with children is that they tend to sort themselves into groups according to the age of their eldest child. In a sense, the child chooses their social group for them. Parents of young children often feel they have less in common with parents of older children and vice versa. To a certain extent this is because talking to each other about their own children is something that people do a great deal, and it helps if the children under discussion are at a similar stage of development or schooling. For many parents, the origin of such a group was their antenatal class. With this in mind, it pays to weigh up whether the people who typically attend a particular course of classes are those with whom you will feel comfortable.