Although possible complications may arise when a woman is giving, it can be stated immediately that, because of the excellence of modern obstetric medicine, giving nowadays is almost without risk – much more so than it was in years gone by. It is likely that many protracted labours and deaths in the past were the result of poor obstetric knowledge and lack of effective drugs and modern techniques. Forceps were not widely used until the eighteenth century and Caesarian sections were practically impossible before the advent of aseptic surgery and anaesthesia. Also women themselves were probably less well-equipped to give than their modern descendants.
In the past the woman’s pelvis was not uncommonly affected by rickets, whereas nowadays the pelvis seems better adapted to delivery. As previously stated, in present times giving birth is a problem only in a minority of cases. And even when it is, years of experience, shared among experts from many nations, ensures that an obstetrician and his back-up team hardly ever have to deal with a situation that they have not successfully dealt with before.
Most women are advised to have their first baby in hospital, even if no complications are foreseen, so that should any difficulties arise, expert help will be available. If a woman’s first baby was delivered normally few obstetricians would raise objections to a home delivery with a midwife in attendance. Midwives are given complete training in all the normal procedures of labour and childbirth, including performing an episiotomy*, and are also taught to recognize those situations and symptoms for which a doctor needs to be called or for which immediate admission to hospital is necessary.
By late, the baby is short of space and can no longer move easily inside the uterus. At this stage, the majority of babies adopt the same position – head down towards the cervix, back towards the mother’s front – known medically as the vertex occipito anterior presentation (occiput , back of the head; anterior, front). A head-first (vertex) delivery is the most safe position for mother and baby. It ensures that the largest and most delicate part of the baby – the head -is delivered first. There is less chance of the umbilical cord getting trapped and, even if it does, once the baby’s head is born it can take its first breath and from that moment on the cord is no longer vital.
The head, although comparatively large and fragile, is in fact designed for a vertex delivery. Because the bones of the baby’s skull are not yet fused together, but are separated by the soft areas known as fontanelles, the head actually becomes smaller as it moves down and through the cervix. This usually takes several hours, during which the separate, soft skull bones are gently pressed together or ‘moulded’ so they overlap slightly. The diameter of the head is therefore reduced, by as much as one centimetre.
Occipito anterior and posterior
The vertex occipito anterior presentation is the best for birth. The baby’s head is flexed, chin against the chest, so presenting the smallest possible diameter to the cervix. If the baby is facing the other way – in a vertex occipito posterior presentation (posterior means back) – it cannot curl up quite so tightly, its head is lifted slightly off its chest and the diameter presented to the birth canal may consequently be greater than that of the cervix even when it is fully dilated. So in an ideal situation the baby turns into an anterior presentation before its head passes into the birth canal.
Usually this rotation happens spontaneously at the end of the first stage of labour; if not,may sometimes be needed to deliver the baby. Because this is rarely necessary, occipito posterior presentations are not regarded as an obstetric problem, although labour may be longer and more tiring for the mother, and there may be constant backache during the first stage as a result of the baby’s spine pressing against its mother’s.
In a normal head-first birth the moulding of the baby’s skull bones happens so gradually that there is no risk of damage. When the head is delivered last, however, as in a breech (buttocks-first) birth, this moulding does not occur. When another part of the baby is outside the mother already, the head has to follow in a short time. This is for two reasons: the body cools down and gives rise to breath-taking reflexes. Secondly, as soon as the head moves down, it tends to trap the umbilical cord, part of which is already in the birth canal. This may restrict the baby’s blood supply. Because moulding has had no chance to occur, the head is consequently slightly larger so that passage through the cervix may be more difficult, yet it must nevertheless be accomplished quickly.
Because of the potential risks to the baby, many obstetricians consider that all potentials should be delivered by Caesarian section. However, a breech baby can be delivered safely vaginally, depending on the size of the mother’s pelvis and the size of the baby; each case is decided on its own merits. For a vaginal delivery, forceps may be used to deliver the head rapidly and protect it from injury.
A woman with a breech baby has a normal first stage of labour. The second stage, too, may go without mishap, but the doctors will be watching to make sure the baby’s buttocks are moving smoothly downwards. If there is some delay an emergency Caesarian section may be necessary. Some breech babies may be delivered foot-first (a footling breech).
Some obstetricians prefer to try and turn a baby out of the breech position before labour starts, so that it can be born head-first. This is done by a manipulative procedure called external cephalic version (ECV). The doctor gently pushes on the baby through the mother’s abdomen to encourage it to adopt a vertex presentation. This is usually done at about 34 weeks ofbut if it does not turn easily the obstetrician will probably leave it. Others among obstetricians object to this method.
They think the risk of complications (for example a solutio placentae*) does not outweigh the risk of a breech delivery.
A very small number of babies lie obliquely across the mother’s uterus or, very rarely, at right-angles to her body (transverse lie). This nearly always happens after at least one pregnancy, when the uterus is larger and its muscular walls less tense than in a first pregnancy. A baby lying obliquely usually assumes a vertex presentation spontaneously just before, or at the beginning of, labour. A transverse lie may be corrected by the ECV technique, otherwise a Caesarian section may have to be performed.