The respiratory tract, similar to other organ systems, undergoes profound changes as a result of the maternal adaptation to pregnancy. Histological findings on respiratory tissues, anatomical relationships, and respiratory function are altered by the gravid uterus and the hormonal and metabolic changes of advancing gestation. Assessing a pregnant woman for respiratory illness involves understanding these changes and interpreting laboratory data in the proper context.
ANATOMIC CHANGES IN THE RESPIRATORY TRACT DURING PREGNANCY
Upper respiratory system — Histologic examination of the upper respiratory mucosa during pregnancy reveals hyperemia, glandular hyperactivity, increased phagocytic activity, and increased mucopolysaccharide content . Pregnant women often experience nasal stuffiness and epistaxis, possibly as a result of these alterations. (See "Recognition and management of allergic disease during pregnancy", section on 'Pregnancy rhinitis'.)
Some women develop benign growths in the nose during pregnancy, leading to nasal congestion and variable degrees of epistaxis . This tumor, which is almost always unilateral, is called nasal granuloma gravidarum, pregnancy tumor, pregnancy granuloma, or telangiectatic polyp. Histologic findings are similar to those in pyogenic granuloma. Nasal granuloma gravidarum resolves spontaneously after delivery in most cases, but it may be excised under local anesthesia if necessary to treat nasal obstruction or frequent bleeding.
The management of epistaxis is reviewed separately. (See "Approach to the adult with epistaxis".)
Thorax and diaphragm — Changes in the thorax and abdomen appear to occur early in pregnancy, well before simple displacement from the enlarging uterus could cause such an effect. In the first trimester, the subcostal angle can change from 68 to as much as 103 degrees [3,4], the diaphragm rises by up to 4 cm, and the chest diameter can increase 2 cm or more . Diaphragmatic excursion is not limited by the uterus, and actually increases by up to 2 cm . The net result of these changes is a more "barrel chested" appearance during pregnancy.