What is preterm labour?
Going into labour before your 37th week of pregnancy is called preterm labour, or premature labour. Preterm labour can cause your baby to be born too soon (premature birth). Although most premature babies develop normally, there may be health problems that affect your baby. The earlier a premature baby is born, the greater the health risks to the baby.
How common is preterm labour?
Recent figures from 2017 show that nearly 9 per cent of babies in Australia were born preterm.
Preterm births are categorised by how early they happen in the pregnancy:
- Extremely preterm (less than 28 weeks)
- Very preterm (28 to less than 32 weeks)
- Moderate to late preterm (32 to 37 weeks).
Can preterm labour be stopped?
In some cases preterm labour can be stopped with treatment (see below). Sometimes it stops on its own. If preterm labour can’t be stopped your baby will be born early. Around one in 10 women with symptoms of preterm labour will go on to deliver preterm.
Symptoms of preterm labour
If you believe you are having preterm labour, get medical help right away.
If you experience any of the signs of symptoms of preterm labour, seek medical help immediately. Once labour is established it is very difficult to stop. Preterm labour may progress faster than term labour. You will probably have to go to hospital.
Signs and symptoms of preterm labour include:
- cervical effacement (thinning) and/or opening of the cervix
- pelvic pressure (feeling that the baby is pushing down)
- constant menstrual-like cramping
- low back pain;
- watery, mucous, or bloody vaginal discharge
- a ‘show’ – when the mucus plug that seals the cervix comes away and out of the vagina
- waters breaking
- 4 or more contractions per hour
- strong contractions – may be painful, unlike Braxton Hicks contractions
What is the difference between Braxton Hicks contractions and preterm labour contractions?
Braxton Hicks contractions are uncomfortable, but not usually painful like the contractions of labour. They occur throughout pregnancy and tone the uterus. The cervix does not open (dilate) with Braxton Hicks contractions.
In contrast, if you are experiencing preterm labour, the contractions will usually be painful and intensify in pain, last more than 30 seconds (becoming longer) and become closer together.
How does the doctor evaluate preterm labour?
Your doctor or obstetrician will try to determine whether you are in preterm labour. They will probably want to keep watch on you for a few hours. The following tests may be done:
- pelvic exam to see if your cervix is opening (dilating)
- uterine activity monitoring to detect contractions
- fetal heart rate monitoring to check the health of your baby.
Fetal fibronectin. In addition, there is a biochemical test that can identify women at risk of preterm delivery. The test involves the measurement of fetal fibronectin, a type of glue created by the body to help the pregnancy bind to the inside lining of the uterus. This substance leaks through the cervix early in the process of preterm labour, and can be detected in vaginal fluid using a simple swab test.
The fetal fibronectin test is not 100 per cent reliable, but if you are experiencing symptoms of preterm labour it can help predict your risk of delivering the baby in the next one to 2 weeks.
Group B streptococcus. The doctor may want to do a swab to test for Group B streptococcus – a type of bacterium that may be present in your genital area and passed to your newborn during labour, causing an infection. If present, the doctor will probably recommend you have antibiotics during labour. All pregnant women are routinely tested for this bacterium at 35-37 weeks.
If you need hospital care
Preterm labour often requires hospital care and complete bed rest. You may need an intravenous line through which fluids are given. You may also be given pills or an injection to help prevent contractions.
Medicines to stop preterm labour
The doctor or obstetrician may recommend you have medicines which can delay birth called tocolytics. Tocolytics are medicines that slow or stop labour contractions. Tocolytics work by relaxing the muscles in the pregnant uterus. They can delay labour, but only for a few days.
One such tocolytic is magnesium sulphate which may be offered to some women to inhibit preterm labour by stopping contractions. It can delay delivery for a few days.
Magnesium sulphate also has a role in neuroprotection of the fetus, meaning it protects the baby’s brain from adverse effects.
The doctor may also suggest you have antenatal corticosteroids – these are to speed up your baby’s lung development and have been shown to reduce their risk of having certain health problems after birth. Even a couple of days of steroids can improve a baby’s lung function while labour is being delayed.
Risk factors for preterm labour
Any pregnant woman can have preterm labour. It may start for no reason. But these risk factors can increase your chances:
- previous preterm labour or premature birth
- multiple fetuses – carrying twins or triplets or more
- use of assisted reproductive technology
- some abnormalities of the baby, cervix (short cervix), uterus or placenta
- a lack of prenatal medical care
- some infections, such as urinary tract infections or vaginal infections (e.g. bacterial vaginosis)
- having certain medical problems, such as diabetes, gestational diabetes, high blood pressure or clotting disorders
- being underweight or overweight before becoming pregnant;
- being under 17 or over 35 years old
- smoking, drug or alcohol use during pregnancy.
Prevention of preterm labour
Some women have risk factors that put them at risk of having a preterm labour, including having had one previously. Depending on what the risk factor is, there may be specific preventive treatments that can reduce a woman’s risk of having a preterm labour.
Cerclage is a stitch that is put in the uterus to help keep the cervix closed. It may be recommended where the cervix is weak (incompetent) and at risk of opening too early. There are some risks associated with this, such as a risk of infection. Your doctor or obstetrician will discuss the risks with you.
Progesterone therapy may be an option for women who have a short cervix to help prevent preterm birth. It works by stopping the uterus from having contractions.
How does preterm birth affect the baby?
A baby born too soon may have health problems, both in the short term and long term. This is because the baby did not have enough time to mature. The baby is at risk of having to be admitted to a neonatal intensive care unit and of needing to stay in hospital longer after birth.
Problems that may affect a preterm baby include:
- not breastfeeding well
- having immature lungs, and not being able to breathe on their own, requiring ventilation
- bleeding in the brain
- life-threatening infections
- newborn jaundice
- necrotising enterocolitis – a serious infection and inflammation of the bowel
- long-term health problems, such as cerebral palsy or heart disease
In an uncomplicated pregnancy, your goal is to get as close to term (40 weeks) as you can before giving birth. The closer you get to term, the greater your chances of having a healthy baby. Work with your doctor or obstetrician. Together you can take steps to try to prevent you from giving birth too early.