Phthalates in certain types of PVC are associated with asthma in both children and adults. While exposure to pesticides is linked to the development of asthma, a cause and effect relationship has yet to be established.The majority of the evidence does not support a causal role between acetaminophen (paracetamol) or antibiotic use and asthma. A 2014 systematic review found that the association between acetaminophen use and asthma disappeared when respiratory infections were taken into account. Acetaminophen use by a mother during pregnancy is also associated with an increased risk of the child developing asthma. Maternal psychological stress during pregnancy is a risk factor for the child to develop asthma.Asthma is associated with exposure to indoor allergens. Common indoor allergens include dust mites, cockroaches, animal dander (fragments of fur or feathers), and mold. Efforts to decrease dust mites have been found to be ineffective on symptoms in sensitized subjects. Weak evidence suggests that efforts to decrease mold by repairing buildings may help improve asthma symptoms in adults. Certain viral respiratory infections, such as respiratory syncytial virus and rhinovirus, may increase the risk of developing asthma when acquired as young children. Certain other infections, however, may decrease the risk. Hygiene hypothesis
The hygiene hypothesis attempts to explain the increased rates of asthma worldwide as a direct and unintended result of reduced exposure, during childhood, to non-pathogenic bacteria and viruses. It has been proposed that the reduced exposure to bacteria and viruses is due, in part, to increased cleanliness and decreased family size in modern societies.
In contrast, a study utilizing 3-D ultrasonography to document the prevalence of the arcuate uterus in a gynecological population found no evidence of increased risk of reproductive loss; in this study 3.1% of women had an arcuate uterus making it the most common uterine anomaly; this prevalence was similar than in women undergoing sterilization and lower than in women with recurrent pregnancy loss. Cause
The uterus is formed during embryogenesis by the fusion of the two Müllerian ducts. During this fusion a resorption process eliminates the partition between the two ducts to create a single cavity. This process begins caudally and advances cranially, thus an arcuate uterus represents an in the final stage incomplete absorption process. Diagnosis
A transvaginal ultrasound can reveal the condition. Helpful techniques to investigate the uterine structure are transvaginal ultrasonography and sonohysterography, hysterosalpingography, MRI, and hysteroscopy. More recently 3-D ultrasonography has been advocated as an excellent non-invasive method to delineate the condition. Differential diagnosis
The major differential diagnosis is the uterine septum. The lack of agreement to separate these two entities makes it difficult to assess the results in the literature. Management
Many patients with an arcuate uterus will not experience any reproductive problems and do not require any surgery. In patients with recurrent pregnancy loss thought to be caused by an arcuate uterus hysteroscopic resection can be performed. Epidemiology
Most studies of uterine malformations are based on populations of women who have experienced a miscarriage and thus do not address the issue of the prevalence in the general population. A screening study by Woelfer et al.