Anatomical differences are common and can be congenital. In some women, cervical incompetence or cervical insufficiency occurs with the inability of the cervix to stay closed during the entire pregnancy. It does not cause first trimester miscarriages. In the second trimester, it is associated with an increased risk of miscarriage. It is identified after a premature birth has occurred at about 16–18 weeks into the pregnancy. During the second trimester, major trauma can result in a miscarriage. Smoking
Tobacco (cigarette) smokers have an increased risk of miscarriage. There is an increased risk regardless of which parent smokes, though the risk is higher when the gestational mother smokes. Morning sickness
Nausea and vomiting of pregnancy (NVP, or morning sickness) is associated with a decreased risk. Several possible causes have been suggested for morning sickness but there is still no agreement. NVP may represent a defense mechanism which discourages the mothers ingestion of foods that are harmful to the fetus; according to this model, a lower frequency of miscarriage would be an expected consequence of the different food choices made by women experiencing NVP. Chemicals and occupational exposure
Chemical and occupational exposures may have some effect in pregnancy outcomes. A cause and effect relationship almost can never be established. Those chemicals that are implicated in increasing the risk for miscarriage are DDT, lead, formaldehyde, arsenic, benzene and ethylene oxide. Video display terminals and ultrasound have not been found to have an effect on the rates of miscarriage.
It has also been found that a low T-helper to T-suppressor ratio is found in aggressive periodontitis which may alter local immune regulation. Monocytes respond to bacterial and inflammatory stimuli with very high levels of local release inflammatory mediators and induce hyper-inflammatory reaction with activation of tissue degrading matrix-metalloproteinases. These is also evidence they produce increased amounts IL-1α and IL-1β which cause osteoclastic bone resorption. These amounts are greatly reduced following treatment.Studies of families, twins and sibling pairs have provided strong evidence for a genetic basis for aggressive periodontitis. A persons genetic predisposition to the condition is determined by a single gene of major effect, inherited as an autosomal dominant trait. However, for the disease process to initiate the person must be exposed to the presence of periodontal pathogens and potentially also various environmental factors. Smoking is a generalized risk factor for generalized forms of aggressive periodontitis. Studies found that smokers have more affected teeth than non-smokers and high levels of attachment loss. This is due to the suppression of serum IgG2 and antibody against Aggregatibacter actinomycetemcomitans found in smokers. Features
According to the 1999 International Workshop for the Classification of Periodontal Diseases, aggressive periodontitis was defined according to 3 primary features, in contrast to chronic periodontitis. These features are common for both localized and generalized form of disease. Primary features
Patients are clinically healthy.Patients do not have any underlying systemic disease that would contribute to aggressive periodontitis.