lower back pain in pregnancy explained

Lower back pain in pregnancy is common. Strangely enough, this is perhaps more true of women who have never before experienced back trouble, whereas women with longstanding low back pain appear to fare quite well during pregnancy.

lower back pain in a pregnant woman

lower back pain in pregnancy comes about for several reasons

  • The weighing down pressures of the foetus on the base of the spine
  • Stretching and separating of the abdominal wall (diastasis recti)
  • Softening of spinal and pelvic ligaments by pregnancy hormones 
  • Weight gain and reduced fitness due to morning sickness

Skip to Sarah Key's The 7 Best Pregnancy Exercises if you want to get started. Or read more to understand what is happening to your body and why the exercises will help

1. The weighing down pressure on the base of the spine
The growing foetus inside the abdomen is a burden; a delightful burden, but never the less a burden. It weighs down heavily inside the uterus and pulls upon the curtains of soft tissue inside the abdomen (the mesentery). This and the supportive uterine ligaments holding the uterus up take origin off the front of the lumbar spinal segments. All this adds greatly to the compressive forces on the lower back and are a direct cause of transient lower back pain in pregnancy. 

Pregnant lady sitting on the floor

The compressive forces through the lower back increase the pressure of the lumbar intervertebral discs. Over time, this leads to dehydration of the discs, making them bulge like car tyres lacking air. All this adds to the low-grade loading strain of the outer walls of the discs, the most likely cause of pregnancy back pain. See Causes of Back Pain

2. Stretching and separation of the abdominal wall
With the massive increase in the convexity of the abdomen during pregnancy all three abdominal muscles layers are stretched, making them less efficient at their job of holding the abdominal wall in. Their stretching also makes the muscular corsetry less efficient at supporting the lumbar spinal base, in effect allowing much more compression of the lower spinal segments. The vertebral compression can lead to quite marked lower back pain during pregnancy.

Sometimes, the increasing size of the uterus during pregnancy causes the rectus abdominis muscles (running vertically up the tummy either side of the midline) to separate. This is called diastasis. There can be minimal separation (one finger) or quite marked separation (say three fingers) which leaves the abdominal wall markedly weaker. Proper abdominal strengthening will reduce separation of rectus abdominis during pregnancy, while also making the pelvic floor's suspensory muscles stronger. 

the importance of exercises to prevent lower back pain in pregnancy

It is important to perform regular abdominal strengthening exercise right through your pregnancy to prevent diastasis, or make it less marked and more easily repaired after delivery. A stronger set of abdominals will also make the labour and delivery more efficient, as they will make getting your strength back (and your figure!) after the birth. However, it is also very important to know the best way of strengthening the abdominals without increasing the bearing down strain on your already heavily loaded pelvic floor. 

3. Softening of the spinal and pelvic ligaments through the influence of hormones
During the late stages of pregnancy the female body gets ready labour by releasing a hormone call 'relaxin' that softens the lumbar and pelvic ligaments. The weakening allows bones of the pelvic to separate slightly to let the baby's head pass through more easily. At this time the mother's body feels weaker and sloppier ~ even more clumsy as it subtly adjusts to its altered centre of mass ~ and it may be relatively easy, especially as fitness levels drop, to suffer a minor (or major) mechanical back straining incident.  


Remember, bending down to cradle and lift your baby is good for your back! A newborn baby is the ideal weight to make you strong again after delivery

Bending 'normally' works the lower (intrinsic) back muscles, the pelvic floor and the abdominal muscles in perfectly synchronised harmony in a way that gathers everything together and allows the ligaments to tighten up again.

Contrary to public opinion, the mother bending over a newborn in a crib is the best way of her getting strong and pain-free again. This information is particularly important for young mothers who have suffered lower back pain in pregnancy and have been advised to keep their back straight. 

A newborn baby weighs say between 6-8lbs. Lifting a baby of this weight is the ideal weight to start the strengthening process of the lower back and pelvis. It is just as important in cases of sciatica during pregnancy.


Bending and lifting normally as a young mother is indeed Nature's way. All you have to remember is to pull the tummy in hard and scrinch up your pelvic floor. You may like to see Sarah Key talking about 'Why Bending is Magic for Backs' in a tailored video on this subject. It is part of the 'Back Pain Treatment Video Package' In the same video, you will also see Sarah doing the squatting exercises which are another way of relieving back pain during pregnancy. 

4. Weight gain and reduced fitness levels through morning sickness
Most women put on weight during pregnancy. Again, this is Nature's way of building up reserves to supply the growing foetus, a hugely demanding presence inside your body, and also preparing her body for breast feeding after the birth.  

Pregnancy is not a time for dieting, but it is a time for keeping fit. Specific pregnancy exercises and walking are essential throughout your pregnancy to avoid excessive weight gain. The right pregnancy exercises will make you stronger and your delivery easier. They will also allow you to get back your normal size and shape more quickly after the birth.

Read about the  7 Best Exercises for Lower Back Pain During Pregnancy

Read about Sciatica and Pregnancy

Read about the 7 Best Stretches for Sciatica During Pregnancy

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