HealthInfo West Coast-Te Tai Poutini

Group B streptococcus in newborn babies

Streptococcus Rōpū B ki ngā piripoho

Group B streptococcus (GBS) is a relatively common normal bacteria in a woman's bowel or vagina. Around 10 to 30% of women have it off and on.

Having GBS in your body is called GBS carriage or colonisation and is not considered to be an infection.

We do not know why some women have GBS and others do not. It is not a sign of ill health or poor hygiene.

You do not need antibiotics if you have GBS carriage during pregnancy. But you will need them if you have a urine infection caused by GBS.

A woman can pass GBS to her pēpi (baby) in 2 ways. The bacteria can move up a woman's vagina and get into the fluid around the pēpi after the waters break. Or the pēpi can pick it up while passing through the vagina at birth.

Most pēpi are not affected but a very small number become infected.

Early-onset GBS infection happens if a pēpi develops GBS infection within 7 days of birth. 70% of affected pēpi have symptoms at birth and 95% by 24 hours after birth. In New Zealand, about 30 pēpi a year get early-onset GBS infection.

Although it is rare, GBS infection is the most common cause of life-threatening infection in pēpi during the first week of life.

Signs of GBS infection include:

• being floppy, or stiff and unresponsive
• poor feeding, or vomiting
• difficulty breathing, or grunting
• high or low temperature
• fast or slow heart rate
• pale or blotchy skin
• irritability
• shrill or moaning cry, or whimpering.

Late-onset GBS infection develops 7 or more days after a pēpi is born. These pēpi may be colonised at birth but probably become infected after birth.

GBS infections after 3 months are extremely rare. Antibiotics given in labour (see below) do not prevent late-onset infection.

Risk factors for passing GBS to a baby

You are more at risk of passing GBS to your pēpi if:

• you have already had a pēpi affected by GBS infection
• you have had a GBS urine infection in this pregnancy
• you have a high temperature (38°C or higher) during labour or when your waters break
• you go into premature labour (earlier than 37 weeks)
• your waters break more than 24 hours before you go into labour (this is called prolonged rupture of membranes)
• you are diagnosed as having vaginal or rectal GBS carriage at 37 weeks in this pregnancy (see below for details).

If you have any of these risk factors, you will be offered intravenous (IV) antibiotics in labour to reduce the chances of your pēpi getting the infection. Your maternity carers will also monitor your baby's health for at least 24 hours after birth.

At-risk pēpi whose mothers do not have IV antibiotics during labour or for at least 4 hours before the birth need to be watched more closely. This includes 4-hourly checks for the first 24 hours.

If you are worried about your pēpi, tell the hospital staff if you are in hospital, or contact your midwife or LMC if you are at home.

Complications caused by GBS infection

GBS causes an infection in a baby's lungs (pneumonia), blood (septicaemia) or brain (meningitis). It can make pēpi seriously ill, and some die from it.

Most pēpi make a full recovery after being treated with antibiotics and intensive care. But even with the best medical care, 5 to 10% of pēpi with early-onset GBS infection die. Most of the pēpi who die from GBS infection are premature (born before 37 weeks).

A few infected pēpi are affected permanently with problems such as cerebral palsy, deafness, blindness and serious learning difficulties.

Rarely, GBS can cause an infection in the mother, such as an infection in her womb or urinary tract. More seriously, an infection in her blood can cause symptoms in her whole body (septicaemia).

Preventing early-onset GBS infection

Most GBS infection in newborn pēpi can be prevented by identifying mothers whose pēpi are at higher risk and treating the mothers with antibiotics during labour.

Tests for GBS

Sometimes women find they have GBS when other tests are done, such as a swab from their vagina or a mid-stream urine sample (MSU).

As GBS comes and goes, it is hard to know if it will be in your vagina when you give birth (which is how it can infect your pēpi). Swabs taken more than 5 weeks before labour are not good at predicting whether it will be there when you are in labour.

If you have GBS any time before 37 weeks, it is best to have a repeat swab from your vagina and rectum (bottom) at 37 weeks. You can take the swab yourself or your midwife or a doctor can do it. Your maternity carers will use the result of this swab to decide whether to offer IV antibiotics during your labour.

Only women at risk of GBS infection are screened before giving birth.

When to contact your midwife or LMC if you have GBS

Contact your midwife or LMC:

• if your waters break
• if you are less than 37 weeks and you go into labour, whether or not your waters break.

Your midwife or LMC will assess you and your pēpi and will talk with you about how to manage your labour.

• Less than 37 weeks. They will offer you antibiotics, as your pēpi is premature.
• 37 weeks or more and your waters break but you do not go into labour within 24 hours. Your maternity carers will offer you induction of labour as soon as possible. They will also recommend that you have IV antibiotics at the start of the induction.
• 37 weeks or more, your waters break. You go into labour, but you do not give birth within the next 24 hours. Your maternity carers will offer you IV antibiotics from 24 hours after your waters break until your pēpi is born.

Treating GBS during labour

If there is a reason for you to have antibiotics during labour and you agree to this, it is best to start them as soon as possible after your labour is established. You will be offered regular doses until you give birth to try to prevent your pēpi getting GBS infection.

Penicillin is the most effective antibiotic for GBS. If you are allergic to penicillin, tell your midwife or doctor so they can offer you an appropriate alternative.

If your midwife, LMC or doctor recommends that you be given IV antibiotics, but you choose not to have them, your pēpi may be at a higher risk of GBS infection. If your pēpi has GBS infection and is not treated with antibiotics, they may become seriously ill and even die.

Risks of antibiotics

Some women have a mild allergy to certain antibiotics and may have temporary side effects such as diarrhoea (the runs) or nausea (feeling sick). Rarely, a woman may have a serious allergy (anaphylaxis) to an antibiotic, which can be life-threatening. But for most women antibiotics are safe. Talk to your midwife, LMC or doctor about the risks and benefits of having antibiotics during labour.

Antibiotics can cause thrush (candida) in women, mostly in their vagina. They can also cause thrush in pēpi, mostly in their mouth or on their bottom (nappy rash). Your midwife or LMC can help you treat this.

Breastfeeding

GBS carriage does not affect breastfeeding. The antibiotics given in labour are safe for breastfeeding.

Caesarean sections

Doctors do not recommend having a planned caesarean section to prevent GBS infection in pēpi. Caesareans have risks for both mothers and pēpi and do not eliminate the risk of GBS infection.

But if you are having a planned caesarean for another reason, we do not recommend having antibiotics, as the risk of your pēpi developing GBS infection is very low.

Things to remember

Many women carry GBS, but GBS infection in pēpi is rare.

Most GBS infection in newborn pēpi can be prevented by giving antibiotics during labour to women who are at risk of passing it to their pēpi.

Even when the mother has antibiotic treatment in labour, some pēpi will still develop GBS infection.

Most GBS infection in newborn pēpi can be treated by giving pēpi IV antibiotics in a neonatal unit.

Written by Christchurch Women's Hospital Maternity Services. Adapted by HealthInfo clinical advisers. Last reviewed November 2024.

Sources

Page reference: 93974

Review key: HIHCP-311277