Fetal and Neonatal Infection

Fetal and Neonatal Infection

• Will cover infections that occur in the pre, peri and post natal periods.

• Baby tends to be susceptible because of– Immature host defences.

– Primary encounter with the organism.

– Some protection from maternal antibodies (passive)

Modes of transmissionThe term “VERTICAL TRANSMISSION” refers to transmission that is unique to a mother/baby relationship. Not all neonatal infections where the mother is the source are transmitted vertically.

in utero (congenital)

intra partum

post partum

genital

transplacental

ascending

others

mother

Infections transmitted vertically

In utero

• Rubella, hepatitis B and C, HIV, CMV, toxoplasmosis, listeriosis, syphilis, herpes.

• Group B Strep, herpes (ascending)

Intra partum

• Hepatitis B and C, HIV, Group B Strep, gonorrhoea, chlamydia, HERPES.

Post partum

• HIV, Group B Strep, herpes

Antenatal screening

• July 2003, Royal Australian and New Zealand College of Obstetricians and Gynaecologists recommends:

• Rubella, syphilis, mid stream urine, HepB(first visit)

• Vaginal swab for Group B Streptococcus.(35 - 37 weeks)

• Variable – HIV, toxoplasmosis, CMV, HepC

Antenatal Screening

• Not clinically obvious in mother

• Presence of a reliable test.

• Likelihood / outcome of transmission.

• Prevalence of maternal infection.

• Possibility of intervention.

A number of maternal infections affect the outcome of the pregnancy, yet we only screen the mother for some infections

Why?

A case for “yes”: Hepatitis B

• Incidence in community is about 1% (Aus).– Higher in some risk groups.

• Risk of transmission to baby is predictable– 90% if chronic active, 10% if carrier.

• Infection with Hep B is always bad, but when infected as a neonate it is worse.– Greater chance of becoming chronic active AND

increased risk of liver cancer AND “spreader”.

• Good intervention with passive and active immunization.

• Risk to HCW in obstetric setting !

Hep B infection: recovery or carrier or chronic active

A case for “maybe”: HIV

• HIV+ mum = 30% HIV+ babies.

• Intervention is possible: reduce to 2%– Antiviral therapy, caesarian birth, bottle feeding.

• Up to 1998 (Aus) 176+ mums and 60+ babies. Estimated 100 new HIV cases in women per year. How many have babies? (assume 10, and 3 babies ? Get HIV)

• Cost of screening 150 000 per year = 15 M

Is $15 million to prevent 3 cases worth it? Could more cases be prevented by spending the $15 million elsewhere?

A case for “no”: CMV

• Cytomegalovirus infection is common and mild in adults BUT can be devastating to the fetus.

• Once infected, we are infected for life, but only a “primary” first time infection while pregnant puts the fetus at risk. (? 1 in 200 pregnancies).

• Risk of transmission is 40%, but outcome is unpredictable (serious to asymptomatic).

• Only intervention is termination.

CMV fails (as a candidate for screening) because the outcome of transmission is so unpredictable and intervention so drastic.

Group B Streptococcus (GBS)

• Does NOT cause maternal disease, but simply colonizes the vagina.

• Transmitted to neonate by the prenatal ascending route, intrapartum or after birth (horizontally NOT vertically).

• Result of transmission to baby– Colonized only (most common)– Early onset disease (septicaemia or pneumonia)– Late onset disease (meningitis)

The most common cause of serious neonatal infection?

1 – 5 per 1000 births

Group B Streptococcus

• Risk factors for transmission AND disease.– Colonized mother.

– Premature birth (less than 37 weeks).

– Prolonged rupture of membranes (greater than 18 hrs)

• Prevention of DISEASE (early onset).– Give intrapartum penicillin (greater than 4hrs pre ‘del)

– Does NOT prevent transmission, but modifies outcome.

– Small risk of penicillin allergy anaphylaxis.

GBS: prevention strategies• Possible areas for intervention.

– Eradicate carrier state in mother – NO.

– Stop transmission – NO.

– Stop colonization becoming disease – YES.

July 2003, RANZCOG

• Vaginal swab culture for GBS at 35-37 wks.– If positive, give penicillin prophylaxis.

• If culture impractical - obstetric risk factors.– Previous GBS infected baby, pre-term labour, prolonged

rupture of membranes.

• Future potential of vaccination.

Rubella (German measles)

• Adult disease– May be asymptomatic or flu like illness with rash.

– Long term immunity follows infection.

– Immunity from vaccine can wane.

• Transmission– Transplacental during viraemic phase.

• Neonatal infection– Most risk during first trimester (90% risk of severe)

– Spontaneous abortion, still birth, deafness, blindness

Rubella prevention and screening

• Routine vaccination of all infants, NOT just adolescent girls.

• Less than 5% of “potential mums” are not immune, and risk of exposure is LOW.

• Antenatal Screening– Screens for maternal immunity NOT disease.

– If NOT immune, cannot vaccinate.

– If NOT immune, can easily prove disease if suspected.

– Termination is only intervention.

Toxoplasmosis

• A parasite of cats and herbivores.• Transmission to humans (common – 45%)

– Old cat faeces or ingestion of poorly cooked meats.

– Mild disease, but infection is lifelong.

• Transmission to neonate– Risk only if mother has first infection while infected.

– 50% of the 0.5% that seroconvert will transmit.

– Transplacental – more severe early in gestation.

– Stillbirth, acute or latent blindness (20 yrs)

Some notable Australian cases linked to kangaroo meat.

Listeriosis• An organism commonly encountered in

food – especially soft cheeses. Can grow in the cold, so refrigeration not a total solution.

• Adult infection– Mild flu like illness – unless immunocompromised.

– Organism gets into bloodstream (Trojan Horse)

• Neonatal infection– Transplacental transmission

– Spontaneous abortion, stillbirth, septicaemia, abscessesPrevention consists of modifying eating habits. At a public health level, screen foods, use pasteurized milk for cheeses.

Neonatal herpes

• Maternal infection can be primary, re-activated or latent. (10 – 20% of Aus women at antenatal clinics are HSV2+)

• Transmission to baby.– Transplacental (rare).

– Intra partum (accounts for most cases)

– Post partum.

• Risk to baby depends on maternal infection.– Highest if primary maternal infection late in pregnancy (50%)

– Less if recurrent (less virus – risk is less than 10%).

– Less if latent and shedding.

Neonatal herpes

• Disease manifestations in baby.– Localized, encephalitis, disseminated.

– Very high mortality, even with therapy high morbidity.

• Prevention (very complicated and non standardized)

– Blood tests poor at distinguishing HSV-1/2 and primary or recurrent or latent in the mother.

– Caesarian section in primary maternal, less convincing for recurrent or latent.

– Antiviral drugs for mother and newborn.

– Counseling for HSV- mothers with HSV+ partners.

Others

• STD’s– Gonorrhoea, syphilis, chlamydia.

• Tetanus