Fetal breathing

In mice and male rats, the oral LD50 was approximately 4g/kg symptoms of toxicity were ataxia and hyperactivity followed by inactivity, loss of muscular tone, labored breathing, clonic convulsions, and death within 2-7 days. Daily administration of 132mg/kg body weight in the diet for 13 weeks decreased the fertility of CD rats 14 days at 96mg/kg altered the estrous cycle of females." In female rats 50 mg/kg injected intraperitoneally on the day of proestrus delayed ovulation and resulted in a lower fertility rate, a reduction of live fetuses, an increase in resorptions, and a slower rate of fetal development. Gavage doses in rats of... 

All of the CNS depressants can pass through the placenta. Newborn babies with dependent mothers may be physically dependent themselves and have withdrawal symptoms that include tremors, irritability, hyperactivity, and feeding and breathing problems. There may be birth defects such as fetal alcohol syndrome, which consists of abnormal facial features, a small head, mental retardation, and poor coordination. 

Glucocorticoids have important effects on the development of the fetal lungs. Indeed, the structural and functional changes in the lungs near term, including the production of pulmonary surface-active material required for air breathing (surfactant), are stimulated by glucocorticoids. 

Effects of low doses of alcohol are considered to be not as dramatic as those of heavy drinking. The occurrence of teratogenic effects decreases when addicted women cut down on alcohol intake or stop drinking altogether after the first trimester (refs. 51, 52). However, McLeod et al. (ref. 60)) found a disappearance followed by a decreased level of fetal breathing movements for 3 hours after the intake of a low dose of alcohol (0.25 g/kg). Therefore, if these movements have a function in the development of the fetus, regular social drinking may have some noxious effects as well. In addition, rat studies have shown that postnatal ethanol treatment can still cause... 

V. McLeod, J. Brien, C. Loomis, L. Carmichael, C. Probert and J. Patrick, Effect of maternal ethanol ingestion on fetal breathing movements, gross body movements, and heart rate at 37 to 40 weeks gestational age, Am. J. Obstet. Gynecol., 145 (1983) 251-257. 

It is not known if exposure to uranium has effects on the development of the human fetus. Very high doses of uranium in drinking water can affect the development of the fetus in laboratory animals. One study reported birth defects and another reported an increase in fetal deaths. However, we do not believe that uranium can cause these problems in pregnant women who take in normal amounts of uranium from food and water, or who breathe the air around a hazardous waste site that contains uranium. 

Nonocular muscle involvement is also prevalent, tanging from fluctuating dysarthria to dysphagia. Because of involvement of muscles that control breathing and swallowing, myasthenia is a potentially fetal condition. No specific pattern of limb weakness occurs, although the proximal muscles are most often affected. 

Salvador HS, Koos BJ. Effects of regular and decaffeinated coffee on fetal breathing and heart rate. Am 1 Obstet Gynecol 1989 160(5 Part l) 1043-7. 

H. H. Szeto, P. Y. Cheng, J. A. Decena, Y. Chen, Y. Wu, and G. Dwyer, Fractal properties of fetal breathing dynamics. Am. J. Physiol. 262 (Regulatory Integrative Comp. Physiol. 32), R141-R147 (1992). 

Hippocratic writers (I) as well as Aristotle (2) assumed that since adults would die without breathing, presumably the fetus also breathed. The precise nature of what actually was breathed was not determined until the discovery of oxygen by Scheele and independently by Priestley in the early 1770s. While the placenta apparently has been known since ancient times, it was not until the work of Harvey (3, 4) that the independence of the fetal and maternal circulations was established. Further convincing experimental evidence for this independence was presented by William and John Hunter (5). 

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