Birth weight is the body weight of a baby at its birth. The average birth weight in babies of European descent is 3.5 kilograms (7.7 lb), with the normative range between 2.5 and 4.5 kilograms (5.5 and 9.9 lb). On average, babies of South Asian and Chinese descent weigh about 3.26 kilograms (7.2 lb). As far as low birth weight prevalence rates changing over time, there has been a slight decrease from 7.9% (1970) to 6.8% (1980), then a slight increase to 8.3% (2006), to the current levels of 8.2% (2016). The prevalence of low birth weights has trended slightly upward from 2012 to the present.There have been numerous studies that have attempted, with varying degrees of success, to show links between birth weight and later-life conditions, including diabetes, obesity, tobacco smoking, and intelligence. Low birth weight is associated with neonatal infection and infant mortality. Abnormalities
A low birth weight can be caused either by a preterm birth (low gestational age at birth) or of the infant being small for gestational age (slow prenatal growth rate), or a combination of both. Potential causes of low birth weight can also be cause by health issues in the person giving birth, genetic factors, or problems in the placenta. A very large birth weight is usually caused by the infant having been large for gestational age. Infants that are large for gestational age have been associated with significantly higher rates of neonatal morbidity.
A change in amino acid 531 from serine to leucine arising from a change in the DNA sequence of TCG to TTG is the most common mutation. Tuberculosis resistance has also occurred due to mutations in the N-terminal region of rpoB and cluster III.An alternative mechanism of resistance is through Arr-catalyzed ADP-ribosylation of rifampicin. With the assistance of the enzyme Arr produced by the pathogen Mycobacterium smegmatis, ADP-ribose is added to rifampicin at one of its ansa chain hydroxy groups, thereby inactivating the drug. Resistance in tuberculosis
Mycobacterial resistance to rifampicin may occur alone or along with resistance to other first-line antitubercular drugs. Early detection of such multidrug or extensively drug-resistant tuberculosis is critical in improving patient outcomes by instituting appropriate second-line treatments, and in decreasing transmission of drug-resistant TB. Traditional methods of detecting resistance involve mycobacterial culture and drug susceptibility testing, results of which could take up to 6 weeks. Xpert MTB/RIF assay is an automated test that can detect rifampicin resistance, and also diagnose tuberculosis. A Cochrane review updated in 2014 concluded that for rifampicin resistance detection, Xpert MTB/RIF was accurate, that is (95%) sensitive and (98%) specific. Pharmacokinetics
Orally administered rifampicin results in peak plasma concentrations in about 2–4 hours. 4-Aminosalicylic acid (another antituberculosis drug) significantly reduces absorption of rifampicin, and peak concentrations may be lower. If these two drugs must be used concurrently, they must be given separately, with an interval of 8 to 12 hours between administrations.