Congenital Infections

Pregnant women have a lot of infections and fortunately only a few of those affect the fetus. A number of years ago – actually many many years ago – we did a study and just in a six week period 30% of the women had some infectious illness during that time. So fortunately most of these aren’t transmitted to the fetus. The thing that bothers me is that a lot of the workup of what are likely congenital infections is either not done or done poorly. Epidemiologic aspects of infections are overlooked, and serologic tests are used inappropriately to make diagnoses. Or, more frequently they are done and you will see on the record TORCH titers done. Negative. And what were done were not adequate to make a diagnosis. So these are what we are going to concentrate on today. The only addition, which I am not going to talk about, would be hepatitis C, which probably should be added to the list although its transmission, compared to hepatitis B, is far less.

The pathogenesis of congenital infections; there are a number of possibilities and the first is that the pregnant woman is infected and transmission to the fetus can be either by the blood, by the placenta, or occasionally ascending infections – frequently with ruptured membranes or leakage of membranes – and then ascending infection, but by and large most of what we will talk about will be by bacteremia or viremia and then via the placenta. The in utero fetus; several things can happen. There can be abortion or stillbirth, can be a one-hit affair, and that is resulting in congenital defects but no continuing infection. Clinical infection which persists throughout pregnancy and involves the infant, there can be asymptomatic infection with recovery. Actually with enteroviruses that happens literally every summer. The infant, as a result of infection, can have acute death, can have persistent infection with manifestations and recovery of infection. Then the child can have late death, late sequelae, or eventual recovery from the infection.

What I’ll do now is go through the individual infectious illnesses. The first is CMV and this, actually as far as frequency of major problems, is the most frequent. There are two events. One is perinatally acquired infection, which is exceedingly common but not too important as far as damage to the baby. Then congenital acquisition which occurs in 0.5 to 2.7% of births. But this results by and large from primary infection in the mother and some 50-90% of women have been previously infected. So even though they may have recurrent CMV infections – and some of them will transmit virus in utero – but by and large infections in those babies don’t result in difficulties. The mothers who are infected shed virus in the urine or cervix very commonly, up to 28%. The infection rate of young adults is about 3% per year but for some reason, pregnant women seem to be more susceptible so it can be anywhere from 3-19% of seronegatives during pregnancy have infection and become seropositive. Fetal infection occurs in 50% of primary maternal infections. Damage to the infant occurs in 10-20% of these in utero infections; primarily primary infections, although there are rare cases of apparent damage with infections in mothers who didn’t have primary infection.

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