This section is from the book "The Home Hand-Book of Domestic Hygiene and Rational Medicine. Volume 2.", by J. H. Kellogg, M.D.. Also available from Amazon: The Home Hand-Book of Domestic Hygiene and Rational Medicine, Volume 2.
Shortness of breath or difficulty of breathing, are frequently among the most prominent inconveniences of the latter stages of the pregnant state. Patients subject to asthema, and suffering with organic disease of the heart, suffer much more than do others. The interference with respiration is produced in most cases by crowding upward of the abdominal organs against the diaphragm, thus preventing its descent, and making it impossible for the patient to take a full inspiration. Shortness of breath is sometimes due to poverty of the blood.
The first class of cases can be relieved but little, as the cause cannot be removed. Some advantage may be derived, however, by the application of faradization to the chest, for the purpose of strengthening the respiratory muscles. In cases in which the difficulty arises from debility, the patient should receive such treatment as will secure improvement of nutrition.
Fainting in some cases occurs quite frequently during the first few months of pregnancy. This is simply due to the morbidly susceptible condition of the nervous system during this period, very slight disturbances being sufficient to occasion intense mental excitement and profound disturbance of the circulation.