Intrauterine Infection and Preterm Delivery

By Helen Harrison

I want to recommend an editorial in American Journal of Public Health entitled "Intrauterine infection and why preterm prevention programs have failed." It is by Drs. Robert Goldenberg and William Andrews at the University of Alabama. The article summarizes the research on the role of uterine infection in very preterm births and offers an interesting hypothesis as to why such infections (which usually go unnoticed) seem to be "timed" to cause delivery between 20 and 30 weeks gestation.

If your baby was born early from preeclampsia, HELLP, or complications of multiple gestation, this may not interest you, but if your child was born early because of unexplained preterm labor and/or membrane rupture, read on...

The authors note that women who deliver prematurely between 20 and 30 weeks are at much higher risk for a repeat very preterm delivery than are women who also deliver prematurely but closer to term. In other words, something different seems to be at work in preterm deliveries prior to 30 weeks, and whatever that "something" is, it tends to recur. Also, babies born below 30 weeks gestation are much more likely to suffer neonatal sepsis than are preterm babies born after that period. It has usually been assumed that this is due to the immaturity of the immune systems of the very preterm babies, but the authors suggest an additional possibility: these babies may have been exposed to bacteria in utero.

The authors point out that up to 80% of women who deliver before 30 weeks have evidence of bacterial infection in the amniotic fluid and/or membranes. Organisms frequently cultured following preterm delivery include Ureaplasma urealyticum, Mycoplasma hominus, Bacteroides, and Gardnerella vaginalis. When such organisms are found in the amniotic fluid of pregnant women prior to 20 weeks, the preganancy usually ends 4 to 8 weeks later.

The authors write: "The findings that infection is so predominantly related to early spontaneous preterm birth, and that early spontaneous preterm births tend to repeat, are likely explained by [the presence of bacteria] in the uterus prior ro pregnancy." The bacteria leads to a chronic low level infection of the uterine lining that generally has no symptoms except for an occasional bout of vaginosis, and often not even that.

The authors continue:"Consider what might happen if the uterus is colonized with bacteria prior to pregnancy. Certainly, conception is not prevented. There is also little evidence that that these women [are more likely to miscarry]. Women who have chronic endometritis (infection of the uterine lining), may however, maintain the infection in an asymptomatic form until the membranes adhere firmly to the decidual lining at about 20 weeks' gestation. Since the membranes usually seal the uterus closed at this time, colonizations (of bacteria) that have been quiescent may only then become symptomatic... Unless the infection is cleared by the body's defense mechanisms, [inflammatory responses to the infection]... will initiate labor and the infant will be born preterm."

"Most strategies to prevent spontaneous preterm birth have been targeted either at treating the symptom of spontaneous preterm labor (tocolytics, uterine monitoring , etc.) or at various psychosocial, behavioral, or nutritional characteristics of the mother statistically associated with, but not causally related to, spontaneous preterm birth. It is not surprising that those strategies have failed."

By contrast, recent randomized antibiotic trials of women at risk for preterm birth showed substantial reductions in spontaneous preterm birth.

So what do you do with this information? It would seem like a good idea to find and copy this article and the studies mentioned in it and take it to your OB to discuss before trying to conceive. A thorough workup for vaginal and uterine infections would be good prior to conception, and because some of these organisms can be passed back and forth sexually, if antibiotics are prescribed, your partner may also need to be treated. Discuss this with your OB. Frequent cultures during pregnancy would also seem to be indicated, with retreatment if necessary.

Also, try to clear up any other chronic infections you may have such as gum disease (gingivitis) which has also been linked to prematurity. It wouldn't surprise me if sinus infections aren't eventually implicated, as well.

One obstetrician writing in the December 1996 issue of Birth stated that the editorial by Goldenberg and Andrews and the research it summarizes "might lead to the dramatic alteration... of prenatal care." Let's also hope it helps some of us on the list to have healthy full-term pregnancies!

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