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Preterm Labor and Preterm Premature Rupture of Membranes
Sponsored by The Indian Health Service Clinical Support Center
2. Background
Case 2
L. B., a 19 y/o G1P0 at 30 weeks by her dates consistent with an 11 week ultrasound, presents with a history of continuous leakage of clear fluid starting approximately 8 hours ago. Her pregnancy has been uncomplicated to date. She is currently experiencing some very mild irregular uterine contractions. She reports good fetal movements.
Background
Preterm labor is a major cause of neonatal morbidity and mortality in the United States . While infant mortality is decreasing due to improvements in neonatal intensive care, the incidence of preterm birth, and of the complications of being born prematurely, are increasing. Over the last two decades, despite improvements in care, the incidence of preterm birth has increased from 9.4 to 11.2 per cent. Nevertheless, survival after 32 weeks gestation has increased to 95 per cent, very close to survival at term. Complications of prematurity are also low after 32 weeks, but morbidity, principally long term pulmonary and neurologic sequelae , remains high in survivors born at less than 28 weeks.
During 2001-2003 (average) in the United States, preterm birth rates were highest for black infants (17.7%), followed by Native Americans (13.2%), Hispanics (11.6%), whites (11.0%) and Asians (10.4%). Peristats: March of Dimes
Prevention
The cause(s) of most preterm births remains unknown and unpreventable. Approximately two third of preterm births are the result of spontaneous preterm labor or spontaneous preterm premature rupture of membranes.
A 2003 literature review found that LEEP appears to be associated with subsequent preterm birth, even when smoking status is matched. Studies with adequate sample size are needed to further evaluate the relationship of LEEP and preterm birth, controlling for potential confounders, including depth of the tissue sample. This was confirmed in May 2004 and careful consideration should be given to treatment of CIN in women of reproductive age, especially when treatment might reasonably be delayed or targeted to high-risk cases.
The remainder of cases are due to a variety of causes, but many are due to unavoidable indicated preterm birth such as those that are the result of life-threatening placental bleeding, or of maternal disorders such as early onset severe preeclampsia . Native Americans have the second highest rate of preterm birth: during 2001-2003 (average) in the United States, preterm birth rates were highest for black infants (17.7%), followed by Native Americans (13.2%), Hispanics (11.6%), whites (11.0%) and Asians (10.4%). Peristats: March of Dimes. There is now extensive evidence that infection is an important etiology of preterm labor, but implications for prevention have not been realized. The role of social and lifestyle factors is also poorly predictive of who will deliver preterm. Prior preterm birth remains the most accurate predictor of recurrent preterm birth.
Role of oral health
Boggess et al reported a large prospective study supports prior research in this field; that is, periodontitis (gum disease) is associated with increased risk for adverse pregnancy outcomes, including preterm birth, low birth weight infants, and preeclampsia. The dose response relationship here is of particular interest; the worse the periodontitis the greater the likelihood of a small-for-gestational-age infant. This ongoing research is also investigating the effects of periodontal treatment on the pregnancy outcome of expectant mothers. Smaller studies have found that "deep cleanings" can reduce the risk of preterm and/or low birth weight infants, probably by decreasing the chronic inflammation and infection associated with periodontitis. Results should be published in 2007. Dr. Todd Smith offers this powerpoint presentation on the impact of oral disease on preterm birth.
Maternal periodontal disease is a chronic exposure to oral pathogens that may represent a treatable condition that contributes to impaired in utero fetal growth. It appears there may be an association, but we need to prove causation. We need an appropriately powered treatment RCT to see if intervention makes any difference. We should be mindful of other recent trends in preterm labor management, e.g., antibiotic therapy of BV / vaginitis in patients in PTL or patients with prior PTB, in which there was ultimately no difference in outcome.
For additional information on periodontitis and adverse pregnancy outcomes, check the web link www.perio.org/consumer/ftm.html and click on "Gum Disease Linked to Pregnancy Complications" and the Archived Press Releases "Periodontal Disease and Overall Health."
Use of progesterone in prevention
Some newer investigations have pointed out the possible utility of progesterone preparations as a preventive measure for recurrent preterm birth in the subset of women with a history of one or more prior spontaneous preterm births. (See Management with Progesterone)
ACOG has now given qualified approval to this strategy. (See ACOG Committee Opinion Number 291, November 2003)
