Your body during pregnancy & birth

There’s a lot going on in your body during pregnancy, as well as during labour and birth…

Your body during pregnancy – hormones

As soon as the placenta starts to form and the cells, which are fast becoming your baby, have implanted into the side of the uterus, your baby will produce human chorionic gonadotrophin (hCG) – these levels will double every couple of days, reaching its peak by about 10 weeks when the levels start to level out as the placenta starts to function.

This hormone is needed to:
*stimulate the placenta to ensure that it grows and works well
*develop your baby’s lungs, liver and kidney
*work with progesterone to grow your breast tissue for milk production
*work with relaxin to loosen your ligaments and joints so your body can expand for your growing baby and to provide the space for your baby to be born

The rapidly growing levels of oestrogen in early pregnancy may cause sickness and nausea.

This is a very powerful hormone – levels are very high during pregnancy.

In early pregnancy it is needed:
*to stimulate blood vessels to increase blood flow to your womb
*for the glands in the lining of the womb to produce the nutrients that are needed for your embryo baby
*to enable the lining of your womb to thicken and to aid the attachment of the placenta and the implantation of your embryo baby
*to form the placenta

Throughout your pregnancy, progesterone is needed:
*for the development of your baby
*to prevent your womb contracting before labour starts
*to prevent lactation until after your baby is born
*to help strengthen the muscles of your pelvic wall for labour

The posterior pituitary gland releases oxytocin during pregnancy, this will increase at the end of pregnancy to stimulate the contractions needed for labour.

Human Placental Lactogen (hPL)

This hormone is made by the placenta, it provides nutrition for your baby and it stimulates the milk glands in your breasts in preparation for breastfeeding.

Your body during pregnancy

Your heart
*during the second trimester your heart is working 40% harder
*your heart rate may increase by about 15 beats per minute
*plasma can increase by 40-50% and red blood cell mass increases by 20-30% which can mean you need more iron and folic acid

Your lungs
*throughout pregnancy, the air going in and out of your lungs increases by about 50%, with higher blood oxygen levels – you could consume 10-20% more oxygen
*the shape of your chest changes in pregnancy as your diaphragm can rise by 4cm, which reduces your lung capacity

Your cervix & uterus
*The cervix acts as a barrier against infection during pregnancy and it protects your baby by staying closed until labour starts. Progesterone causes the cells of your cervix to create mucus, which forms the mucus plug.
*Your uterus will contract throughout pregnancy – these Braxton Hicks contractions helps the blood circulation to the placenta.

Nausea and vomiting
*This affacts about 70% of women – it is usually caused by relaxed stomach muscles and increased oestrogen
*About 20% of women will experience this throughout their pregnancy.

About 50% of all pregnant women will have an increased appetite.

This affects 30-70% of women at some point during pregnancy – it is caused by progesterone, which relaxes the oesophageal sphincter.

Weight Gain
This is expected to be: 4kg (9lb) in the first 20 weeks and 8.5kg (1stone 5lb) in the last 20 weeks, making 12.5kg (1stone 13lb) in total – but this can vary a lot.

*Boobs: 0.4kg (1lb)
*Fat: 3.5kg (12lb)
*Placenta: 0.6kg (1lb5oz)
*Baby: 3.4kg (7lb 7oz)
*Amniotic fluid: 0.6kg (1lb 5oz)
*Increased uterus size: 1kg (2lb 3oz)
*Increased blood volume: 1.5kg (3lb 5oz)
*Extra fluid: 1.5kg (3lb 5oz)

Your skin
Half of all pregnant women will experience deeper colouring on their face – it is more common in dark-haired women.

This increases by about 0.5C due to increased progesterone and blood supply.

The anterior pituitary gland can double in size, which can cause headaches in pregnancy.

Your boobs
Breasts can swell due to increased bloody supply and hormones:
*oestrogen – for the growth of lactiferous tubes, ducts and fat
*progesterone – stimulates the alveoli buds and their ability to secrete milk
*prolactin – for the production of colostrum

Your body during labour

For your baby to be born, the muscles of your womb need to contract and your cervix needs to soften and open – a balance of hormones working together makes this happen.

*oxytocin stimulates the uterus to create contractions and, with a high level of oestrogen, creates prostaglandins, which softens and opens the cervix.
*relaxin increases in labour to soften and improve the flexibility of your cervix, uterus and pelvis to aid the birth of your baby.
*beta-endorphins – your natural opiate – is released to help you manage your contractions. It also aids the production of prolactin and prepares your baby’s lungs for birth.
*high levels of adrenaline are produced when birth is close, to give you a surge of energy as well as the powerful contractions you need to give birth to your baby.
*prolactin is produced throughout pregnancy but levels peak when your baby is close to being born and then remains high to produce milk while you breastfeed.

Your hormones after labour

*oxytocin will continue to be produced after your baby is born, to create contractions to aid the birth of your placenta. Along with prolactin, it helps to boost feelings of happiness and love so you will protect and look after your baby.
*beta-endorphins are also crucial for breastfeeding – levels peak about 20 minutes after giving birth. It also exists in breastmilk to create a mutual bond between you and your baby.
*prolactin is produced so your breasts can make milk. With oxytocin and beta-endorphins, it also helps to create euphoria in new mums.

And this is just the basics – there is a lot going on in your body during pregnancy, labour and shortly after birth.

This information was gathered from:
Mayes Midwifery
Anatomy & Physiology for Midwives
Myles Textbook for Midwives
Dynamic Positions For Birth