Why your baby may have arrived early

​There are many reasons why your baby may have been born preterm. Your early delivery may have been planned in advance, or it might have been unexpected.

Common reasons for a spontaneous preterm birth

An infection within the uterus or vagina (such as a urinary tract infection)

There is evidence to show that the presence of certain bacteria in the urine, even if there are no signs of infection, can cause premature labour. 

It is now recommended that all women have their urine tested for bacteria early in pregnancy. Treating the infection may reduce the risk of premature labour. The vagina can also contain bacteria, and this may contribute to a premature birth.

A weakness in the neck of the womb (often called ‘cervical incompetence’)

This is when the muscles that close the neck of the womb (cervix) are weak. The weight of the baby may cause the cervix to open in the fourth or fifth month of pregnancy. You may be offered a stitch called a Shirodkar suture which is tied round the cervix to try to prevent it from opening too early in pregnancy. 

This kind of stitch can sometimes help women who have had repeated miscarriages because of a relatively weak cervix. The stitch is usually inserted at 14 weeks and removed at 37 weeks. It can also be put around the cervix in the early stages of pregnancy to help keep it closed.

This is when the waters break before 37 weeks’ gestation. It can be caused by a bacterial infection. Most women go into spontaneous labour within 24 to 48 hours of their waters breaking.

Common reasons for a planned preterm birth

Multiple births

Women go into premature labour in nearly half of twin pregnancies – far more often than women carrying only one baby. Overall, about one-third of women pregnant with twins who go into premature labour end up delivering early.


This is a disorder that only occurs during pregnancy and after pregnancy, affecting about 8-10% of all pregnancies. It affects both the mother and the unborn baby and is a rapidly progressive condition characterised by high blood pressure and the presence of protein in the urine. 

Typically, pre-eclampsia occurs after 20 weeks’ gestation in middle to late pregnancy, although it can occur earlier.

Medical conditions detected in the womb

During your pregnancy you will have had several tests and procedures to ensure your baby is growing well without any complications. 

However, in some instances, a condition or complication may have been detected. For many reasons an early birth would have been planned and your baby admitted to a neonatal unit for their ongoing care and needs.

The information on this page is more than two years old.