जन्म का शरीरक्रिया विज्ञान

Gap junctions and the active stage of late pregnancy

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There is a transitional phase of activity in late pregnancy when the body is changing from working to keep the baby in, to working to help the baby out.

This phase can happily stop and start (or continuously trickle) for many hours or days while all the final behind-the-scenes preparations are made. When this activity is noticeable (it isn’t always) it is referred to as prodromal labour or as the latent stage of labour, but it may be better to think of it as the active stage of late pregnancy and to carry on with normal life accordingly.

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Physiology and the length of pregnancy: when does labour start? 

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No one really knows for sure why labour starts when it does but there is growing evidence that babies play a significant part by sending chemical messages to their mothers’ bodies that they are ready to be born, and that labour starts spontaneously when both mother and baby are prepared, physically and neuro-hormonally, for optimal labour, birth, and early postnatal wellbeing.

 

The length of a normal healthy pregnancy varies widely and ‘term’ (when the baby is considered to be mature) is given in the text books as being between 37 and 42 weeks of pregnancy, a range of 35 days.

 

A study in 2013 looking at the natural length of human pregnancies agreed with this figure.

 

It is important to note though that they excluded babies born before 37 weeks (when many babies born shortly before this time are ripe and ready to go), and they excluded babies born by caesarean section or induction before the natural onset of labour, with twenty-four percent of respondents later reporting medical interventions that had artificially shortened their pregnancy.

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Therefore we have no idea how long those pregnancies would have been and so the study, while confirming that the usual 40 week mark is only one day within a wide range, does nothing to show us the true limits of that range.

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Birth environment and the mind-body connection

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Thinking of the ‘tuning-up’ phase as a normal phase of late pregnancy (rather than early labour) means that the labour ‘clock’ has not started ticking in our minds, and that carrying on with normal life feels little different from carrying on through any of the other ‘minor discomforts’ of pregnancy. Amish women in America, who tend to have shorter (and apparently easier) labours, carry on with the housework, only calling the midwife when the birth seems close.6 Unless we are living in danger, the normalcy of the home environment and home routines has a positive effect on the physiological process because this is generally where we are at our most relaxed - and at our least inhibited. The thinking brain has little to do with it.

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The older part of the brain listens to our sensory input and when things look, sound, feel, smell and taste like home, stress hormones are at their lowest and the autonomic nervous system is balanced in favour of supporting the birth process. However, the older brain also listens to our beliefs so that, even at home, if each wave of tightening is greeted by the belief that labour is inherently impossible or dangerous, or that the sensations of normal labour are insufferable, the balance may tip the other way until the mother is helped to feel confident and safe again. Thus, not only is it the physical environment that affects the physiological process, but also the cultural environment from which the mother has shaped her belief system.

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Furthermore, the beliefs of her birth attendants will also have an affect on labour progress. Other people’s doubt and fear is very infectious and once ‘breathed in’, it becomes our own.