Chorioamnionitis, preterm birth, and asthma

Is asthma predetermined in the womb? The results of a recent study point to this. Chorioamnionitis is an infection of the uterine cavity caused by bacteria. When chorioamnionitis occurs together with premature delivery, which is very likely, the risk for asthma in the infant increases dramatically. And the risk increases even more among in children of certain ethnic groups. African American babies for example, have double the risk than other ethnicities, according to a report in the LA Times.

Let us take a look at some statistics from the report:

• About 8% of pregnancies are affected by chorioamnionitis.
• About 14% of American children are afflicted with asthma.
• About 50% of asthma cases are hereditary.
• African Americans have 25% higher incidence of asthma compared to other ethnic groups.

The study used data from the Kaiser Permanente Southern California (KPSC) Matched Perinatal records of 510,216 singleton infants born between 1991 and 2007. The aim of the study was to examine the association between chorioamnionitis and childhood asthma based on gestational age at birth and race/ethnicity.

The results indicate that the combination of premature birth and chorioamnionitis greatly determines asthma development as children grow older. African American children have 98% higher risk of developing asthma before age 8 years. In Latin American children, the risk is 70% higher, and it is 66% higher among whites. No increased risk was found in Asian or Pacific Islander children. No increased risk was also found among kids who were born at full term.

About chorioamnionitis:

Maternal chorioamnionitis or simply chorioamnionitis is characterized by inflammation of the chorion and the amnion, the membranes that surround the fetus. Chorioamnionitis usually is associated with a bacterial infection. This may be due to bacteria ascending from the mother’s genital tract into the uterus to infect the membranes and the amniotic fluid (source Medicine.net).

There is indication that a large proportion of preterm births is directly or indirectly linked to some form of infection, including chorioamnionitis. Signs of placental inflammation have been observed in 42% of infants with extremely low birth weight infants.

The incidence of chorioamnionitis is difficult to determine but it is known to be higher in underdeveloped countries than in developed countries. Its occurrence declines as pregnancy advances toward term gestation. It is also estimated that 40 to 60% of all preterm births are associated with some kind of infection, including chorioamnionitis. The risk of chorioamnionitis depends on health conditions and behaviours but also on gestational age and socioeconomic factors such as economic status, and ethnicity.