What happens in labour
In medical terms, the first stage starts when your contractions bring about the opening (dilation) and thinning (effacement) of the cervix, and ends when these are complete. At this point, your midwife will confirm that you are fully dilated.
It's difficult to be sure about the onset of labour as it differs from woman to woman. Certain classic signs - intense contractions, dilatation and thinning of the cervix, and rupturing of the membranes - are taken to mean that labour is underway.
Contractions during labour
When true labour starts, the nature of your contractions changes. They become more rhythmical, more painful, and they come at regular intervals. These contractions are not within your control and, once they have begun, won't stop until your baby is born.
You can time your contractions from the start of one contraction to the start of the next. In early labour, contractions are usually 30-60 seconds long and come at intervals of five to 20 minutes. This can vary as some women may not notice their contractions until they are closer together, say every five minutes. During the active phase, contractions usually last 60-90 seconds, at intervals of two to four minutes.
As your uterine muscles tighten, you may feel something like menstrual cramps, spreading around your lower abdomen like a tight band. This is because the uterine muscle becomes short of oxygen as its blood vessels are compressed. The uterus is a huge muscle and needs a lot of energy during contractions.
Every woman feels contraction pains differently, but in early labour they may be similar to menstrual cramps or a mild backache. Some women experience severe backache. Very often a contraction feels like a wave of discomfort right across your abdomen that reaches a peak for a few seconds and then diminishes. At the same time, you can feel a hardening and tightening of the uterine muscle, which is held at the peak of its intensity for a few seconds before the muscle begins to relax.
Women assume that contractions will get steadily longer, more frequent, and stronger. This is not so; don't be disturbed if your contractions seem to vary. It's as normal for a strong contraction to be followed by a weaker one that doesn't last quite as long as it is for contractions to follow one another relentlessly.
Your cervix dilates and thins during labour
The cervix is usually a thick-walled canal about 2cm ( ¾ in) long, and firmly closed. In the last few weeks, pregnancy hormones may soften your cervix, but the intense contractions of first-stage labour are needed to dilate and thin it. Dilation is measured in centimetres from 0-10cm (up to 4in). Your cervix will only dilate about 4cm (1 ½ in) during the latent phase, then progress to 8cm (3in) in the active phase. The pain increases as it becomes fully dilated during transition. Eventually, the whole cervix opens up and is made one with the body of the uterus, creating a continuous channel that your baby can pass through.
Your waters break during labour
The membranes of the amniotic sac may rupture painlessly at any time during labour, although this usually happens towards the end of the first stage. Fluid may leak or gush out; the flow depends on the size and site of the break and whether or not the baby's head is plugging the hole. Usually, if the membranes rupture spontaneously near term, labour follows within a short time, although occasionally it's delayed.
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