Opinion: What did pregnancy do to my gut? From nausea to constipation and farting
29 November 2022
The following opinion piece, co-authored by Dr Vincent Ho from the School of Medicine and Adjunct Fellow, Dr Kate Levett from the NICM Health Research Institute, was first published with full links on The Conversation (opens in a new window).
It’s two weeks after the birth of your healthy bub and you notice your gut isn’t feeling quite right. Maybe you feel a bit bloated. Maybe you’re farting more than usual.
What’s going on?
Pregnancy changes the structure and function of virtually every organ system, including some big changes to the gut. These changes can explain some common symptoms.
And no, you’re not imagining it. Some gut symptoms, such as constipation and gassiness, can hang around after you’ve given birth.
Nausea is common
The most common gut symptom in pregnancy is nausea, which affects up to 85% of women in the first trimester.
This is thought to be largely due to the effects of the hormone human chorionic gonadotropin.
Levels of the hormone are highest at the end of the first trimester and start to level off for the rest of the pregnancy. That explains why nausea tends to become less common as your pregnancy progresses.
Reflux can be painful
Other hormonal changes can lead you to develop another common symptom, reflux.
Levels of the hormone progesterone, for instance, steadily rise over the course of a pregnancy. This can lead to the oesophageal sphincter muscle – which is at the lower end of your food pipe, before it meets the stomach – to become more lax.
The loosening of this muscle makes it easier for stomach acid to move back up into the food pipe. This can cause a painful burning sensation in the upper part of your abdomen or just behind the breastbone.
Later in the pregnancy, your growing uterus and baby can start to really push up on your stomach.
This can also lead to reflux as direct pressure on the stomach forces stomach acid back into the food pipe.
Is constipation normal? And haemorrhoids?
Increased levels of progesterone and the hormone oestrogen lead to a decrease in muscular contractions (peristalsis) throughout the gut.
This means you’re more likely to become constipated during pregnancy. Constipation affects about 40% of pregnant women.
Increased levels of oestrogen also lead to your blood vessels and connective tissue (tissue that connect one type to another, such as ligaments) becoming softer.
This, plus pressure from the growing baby, and increased blood volume and flow, can contribute to the development of haemorrhoids – columns of cushioned tissue and blood vessels found close to the opening of the anus.
Your body also needs more water and sodium in pregnancy to help produce amniotic fluid (liquid that surrounds the growing baby in the uterus) and build the blood supply of the growing baby. This necessary water and sodium is absorbed from your intestines and can contribute to constipation, and an increased risk of haemorrhoids.
Haemorrhoids are very common during pregnancy. One study found 86% of pregnant women reported them.
No wonder I feel full
Oestrogen is thought to be responsible for decreasing the movement of the stomach in pregnancy, keeping the food in the stomach longer and making it more likely you’ll feel full.
During the third trimester, your growing uterus and baby also start to really push up on the abdominal organs. No wonder you’re likely to feel pressure on your stomach and discomfort the closer you are to the end of your pregnancy.
You can also feel pressure at the other end of the gut. Pressure from the expanding uterus on the end part of the colon (the sigmoid colon) can also make you feel constipated even if you’re not.
I have incontinence. Is that because of how I gave birth?
There has been a lot of debate about whether urinary or faecal incontinence is more likely after a vaginal or a caesarean birth.
However, the strongest evidence we have suggests the mode of birth makes no difference. If you’ve had incontinence during pregnancy this is the strongest predictor of having it afterwards.
Urinary incontinence that doesn’t improve within three months of giving birth is more likely to persist. So if you’ve experienced this during pregnancy, you might like to see a pelvic floor physio.
Fortunately, faecal incontinence after pregnancy is very uncommon, affecting only around 3% of women. However if this persists, please seek medical attention.
Why am I still constipated?
A study from Finland on more than 400 women found constipation affected 47% of women in the first few days after a vaginal birth and 57% of women in the first few days after a caesarean.
The researchers suggested this may be caused by too much physical inactivity and insufficient intake of fluids after birth, or the effects of anaesthetic and disturbance to the intestines during surgery.
One month after childbirth, constipation became less common. Some 9% of women were constipated after a vaginal birth and 15% after a caesarean.
Feeling gassy? No, you’re not imaging it
The Finnish study also found excess farting is extremely common a few days after birth. It affected 81% of women but this number dropped to 30% one month after birth.
Bloating is another common symptom found a few days after birth affecting 59% of women, and this decreases to 14% of women one month afterwards.
So why is this happening? We can look to your gut microbiome for clues. This is the unique universe of micro-organisms (bugs), and their genes, that live in your gut.
During and after pregnancy, there are profound changes to the gut microbiome. These may cause an increase in gas production or lead to constipation.
So the good news from the Finnish study is that normal bowel function is restored quickly after childbirth for most women, but might be a touch longer for women after a caesarean.
Author's Note: If you’re concerned about gut symptoms during or after pregnancy, seek advice from a health-care professional, who can discuss treatment and referral options.