Breech presenting babies occur in about 4% of pregnancies at full term (over 37 weeks of pregnancy).
Most of the time we don’t know why your baby is breech; the baby is well and healthy but it just happens to be breech.
For a few babies the reason that they are breech is due to a condition (for example Down Syndrome) that reduce their movement in the womb meaning they cannot turn to head down towards the later part of your pregnancy. Most conditions like this are discovered during the tests you will be offered in pregnancy such as ultrasound scanning and the screening tests in early pregnancy. Sometimes the conditions are such that it is difficult to know before birth so all babies regardless of the position they are born are given a first medical check within 3 days of birth where a condition may be apparent.
Some studies suggest that there are increased chance of breech can also be linked to using some medications in pregnancy. Mothers taking medications that sedate (such as antiepileptic drugs, opiates) will also decrease the activity of the baby in the womb meaning she / he will be less likely to move head down towards the end of pregnancy. Additionally severe alcohol use can reduce the movement of the baby in the womb and increase the chances of breech.
Babies born early (premature birth) have a higher chance of being breech as babies tend to turn to head down as pregnancy continues. In mid pregnancy the baby won’t have a fixed position, but move around the womb as he/she grows.
If you have low amniotic fluid (liquor) in the womb this may restrict the movement of the baby, lessening the chance of it turning to head down. Similarly, if the umbilical cord is very short or placenta is in a particular position both of these things may restrict your baby’s ability to move in the womb. These issues can usually be picked up on scan.
Occasionally the baby can be breech due to the shape of the womb (for example bicornate, heart shaped, uterus) or when fibroids (tissue deposits) are in the womb that stop the baby turning to head down position. Again, most of these things you may already be aware of or they can be seen if you have chosen to have ultrasound scans in pregnancy.
In the East, breech is thought to be associated with emotion, stress or unhappiness during pregnancy. The theory being that the baby wants to be nearer to the mother’s heart for comfort.
There is also some evidence that having a breech baby in one pregnancy will also increase your chances of having another breech baby in subsequent pregnancies. A woman who has had a previous breech birth has a 1 in 10 chance of having a breech birth in the next pregnancy and following 2 previous breech babies a 1 in 4 chance of a breech baby in a third pregnancy. This may be down to particular anatomy such as pelvic shape.