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The uterus, hormones
and labor: A summary
By Natalie Burgess
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How the uterus works |
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Hormones in labor and birth |
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Stages of labor and birth |
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Why we feel pain in labor |
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Natural methods of pain
relief |
How the uterus works
The uterus is the most amazing muscle and it is designed to grow
with our beautiful babies, keep them snug and also provide a support structure
for the placenta. The uterus is made up of muscle fibres that are similar to
the muscles in our arms or legs that is they are designed to stretch, relax and
maintain tone. The uterus has the extra special ability to retract.
The uterus does not have nerve fibres that cause pain. The only time you will
feel pain as a direct result of your uterus is if it is forced to work against
itself. The uterus requires lots of oxygen to work effectively in labor so when
someone tells you to breathe through a contraction, it is helping to provide
oxygen to your baby and to your uterus (aerobic metabolism). If we don’t breathe
effectively the uterus begins to tire, and when in established labor
contractions do not generally stop, so it starts to use its own stored energy
reserves in the muscle (anaerobic) and this causes the beginnings of uterine
discomfort.
The uterus contracts in labor to facilitate the opening of the cervix (all the
way up to 10cms),
and is composed of 3 layers:
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Perimetrium – the outer
aspect of the uterus |
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Myometrium – the middle
muscular layer of the uterus |
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Endometrium – the inner
vascular layer |
The Myometrium consists
further of:
1. The inner layer has muscle fibres that run around the uterus. This layer
draws the muscles of the uterus up to the top, or fundus, and as labor advances
the fundus becomes thicker and the lower segment of the uterus gets thinner.
2. The middle layer is a criss cross of blood vessels that supply the uterus
with all the oxygen it needs.
3.The outer layer is made up of long muscle fibres that run up and down the
length of the uterus and help the cervix dilate.
The uterus is designed to contract and maintain muscle tone following each
contraction, and works rhythmically in response to the work of the muscle layers
and hormones in labor.
Hormones in labor and birth
There are 3 main hormones that affect labor, the work of the uterus, and birth:
1. Oxytocin
Known as the love
hormone, as it is released in men and women during orgasm and nipple stimulation
(that’s why nipple stimulation can help induce labor). This amazing hormone is
released in large amounts during pregnancy, helping with nutrient absorption via
the placenta and helping to reduce stress levels, plus also promoting sleep.
Oxytocin
is responsible for rhythmic uterine activity (contractions) and also facilitates
the birth of your baby. Immediately prior to birth Oxytocin levels
increase to stimulate powerful contractions, like is experienced in transition,
to help birth the baby quickly and easily (another reason to not push until you
have uncontrollable urge). This is known as the Maternal Fetal Ejection Reflex.
2. Endorphins
Our body's natural opiate, which work by filling up pain receptor sites.
Endorphin levels rise in pregnancy promoting feelings of wellbeing, and
reach optimal levels at around 38-40 wks just prior to the body going into
labor. Endorphins continue to rise in an undisturbed labor.
3. Adrenaline
Released when we are fearful, anxious, stressed etc. When Adrenaline is
released we 'fight or fly' and all non essential body systems are put on
standby, which includes the uterus. If we are fearful in labor Adrenaline
is released and blood is diverted away from the uterus meaning the uterus gets
less oxygen (as does your baby) and starts causing discomfort.
Adrenaline also negates endorphins which results in no natural pain
relief hormones and Adrenaline reduces Oxytocin levels causing
contractions to slow down or stop all together.
Adrenaline
does have its place in
birthing, as levels of Adrenaline rise immediately prior to birth causing
the mother to become alert to the imminent birth of her baby and find a safe
place to give birth. Adrenaline also ensures the baby is born alert,
helping to initiate the first breath and facilitate the first breastfeed.
So what does this all mean?
We need to remain relaxed and calm to encourage Endorphin release and
allow our body (and Oxytocin) to do the work it was designed to do,
working with your body to birth your baby.
Adrenaline is not beneficial in labor (but has an important role at the
end) and has a negative impact on the baby as it decreases their oxygen supply
by diverting blood away from the uterus. Adrenaline in labor impacts on
the mother causing labor to be longer/or disrupted, hence the term some of you
may have heard 'failure to progress'. Contractions can also become more painful
as the uterus has to work harder and longer.
So why do we feel pain in labor?
So far -
1. If the uterus has to work without oxygen.
2. If we are fearful, which releases Adrenaline and decreases
Endorphins (natural pain relief) and decreases Oxytocin, meaning a
longer labor and more chance of medical intervention.
Stages of labor and birth
Prelabor
Pre labor can be experienced
for up to 2 weeks before true onset of labor and may include:
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The loss of your mucus plug
(show), which may be blood stained or clear mucus |
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Babies head engaging in
your pelvis (but not necessarily if this is not your first baby) |
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Increasing Braxton Hicks
contractions as the uterus ‘warms up’ |
There are 4 stages of labor:
1. First stage is divided into latent and active labor
0-4cms (latent stage)
effacement (thinning) and dilation of the cervix
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Contractions are mild to
moderate in intensity, and may even be irregular, perhaps occurring
3-10minutely (this is different for every labor) and lasting anywhere from
30-60seconds |
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This is the part of your
labor where it is best to stay somewhere you feel safe and secure, rest and
relax
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4-10cms (active stage)
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This is the stage of labor
where the uterus kicks up another notch and the contractions become more
intense and regular, lasting 60-90 seconds and occurring 2-5 minutely (again
just as a guide) |
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If your waters remain
intact this cushions the action of your baby's head on your cervix, softening
the intensity of the contractions. Mother nature giving us a helping hand |
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Generally your waters will
break sometime in the active stage of labor around 7cm |
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Towards the end of the 1st
stage you enter transition, which for many women is the most challenging part
of their labor |
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Remember the work of the
hormone Oxytocin which reaches peak levels just prior to your baby
being born and causing very intense contractions as the uterus works to fully
dilate the cervix and birth your baby |
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Transition is often the
stage at which you may request your personal method of pain relief |
2. The second stage
of labor is from fully dilated to the birth of your baby
The body is an amazing thing
as often a laboring woman will reach 10cms dilated and the uterus will actually
take a break, contractions will ease off or stop for 5-30minutes of so giving
the mother and her baby a bit of a break before the work of birth, this is
normal and allows the baby to have lots of oxygen and the mother an opportunity
to refocus, refresh and revitalise.
As the baby moves down into the vagina, its head places pressure on the
posterior wall of the vagina, stimulating the overwhelming sensation of pressure
(which for some women feels like needing to do a poo) and then an uncontrollable
desire to push, which leads to the baby being born.
3. The third stage is the birth of the placenta
4. The fourth
stage
This stage is often not
discussed in most standard childbirth education classes but it is a very
important stage.
This is the first 2hrs after the birth of your baby: for bonding, the first
breastfeed and just getting to know each other.
A lot of focus is placed on the labor and birth but this stage is vital for the
release of hormones in the mother to help with milk supply, the first breastfeed
for the baby (and subsequent breastfeeding success) and also helps to reduce the
onset and severity of symptoms associated with PND (postnatal depression).
Why we feel pain in labor
So why do we feel pain in
labor?
First the
definition of pain: an individual’s interpretation of a sensation (basically),
so everyone feels differently.
Fear of labor and birth (for
many women) comes from stories we have heard at our mother’s knee, media
dramatisation, stories from well intentioned friends and the social expectation
of pain.
The fear surrounding childbirth helps to initiate and set in place the
fear-tension-pain syndrome, simply put, if you are frightened you become tense
and when you are tense Adrenaline is released initiating the fight or
flight response (remember back to how Adrenaline affects labor), and
then we feel pain.
We need oxygen so that the uterus can work to its full potential, and also to
keep our baby happy. If we are fearful, our breathing becomes short and tense,
decreasing our oxygen levels leading to an unhappy baby and a oxygen deprived
uterus, leading to pain (as the uterus struggles to work this leads to a
disrupted and prolonged labor) and dips in the babies heart rate with every
contraction (fetal distress).
The uterus does not hurt in labor but the cervix has lots of nerve fibres and
the sensation of the cervix opening, stretching and being pulled up can be
painful for some women at the peak of a contraction and in transition, and for
others it is simply 'intense' (remember that intact waters cushions the impact
of the babies head on the cervix decreasing the intensity sensations experienced
by the laboring mother).
I'm of course not saying that you will not feel pain but every experience is
different, and everyone interprets the sensations differently and this is why
relaxation and yoga is effective as pre birth preparation, working to train the
mind to interpret the sensations as a positive experience and calms and relaxes
the laboring women to allow the body to work as effectively as it can.
Natural methods of pain
relief
1. Gate control theory
Basically you can shut the
'gate' to the cervix nerve impulses in the spinal cord (before they reach the
brain and are interpreted as a painful or intense sensation) by stimulating
other nerve impulses that flood the 'gate'. These nerve impulses can be
triggered by:
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Light touch |
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Massage |
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Counter pressure, in
particular counter sacral pressure |
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Hot or cold to the skin in
particular the lower back/sacrum |
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TENS (transcutaneous
epithelial nerve stimulation) |
2. Endorphin release
Our wonderful natural pain
relief is encouraged by feelings of safety, security and calm
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Familiar smells
(aromatherapy) |
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Sounds (music) |
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Regular relaxed breathing
(just simple in and out, no holding the breath or tensing the breath) |
3. Distraction
Flooding the brain with other
sensory stimulation to process
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Vocalising/chanting (which
also encourages great breathing) |
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Rocking (pelvic rock) |
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Music |
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Key words that your support
person uses to help refocus you during a contraction |
4. HypnoBirthing
(BirthSkills)
This is a method of learning
to relax the conscious mind and release fears surrounding childbirth, pregnancy
and mothering through education and preparation plus learning how to apply
relaxation and breathing tecniques in labor.
5. Positioning
The use of various positions
to encourage optimal fetal positioning to reduce discomfort and length of labor,
plus positioning to optimise birthing hormone and in particular endorphin
release.
For further information see
Yoga for Pregnancy
and Birth article
Natural methods of pain
relief work in conjunction with a calm and relaxed mother, a supportive and
nurturing support team/partner and a caregiver who will simply sit and observe,
wait and listen, guide and encourage.
Copyright ©
Natalie Burgess 2007
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