Aetiology

• the definitive cause of pregnancy rhinitis has not been identified
  • various theories on the aetiology of pregnancy rhinitis have been postulated
    • initial hypotheses on the aetiology of pregnancy rhinitis included oestrogen effects, hormone allergy, stress, and increased blood volume with resulting nasal airway resistance
    • study evidence has revealed that levated serum placental growth hormone as well as increased serum house mite IgE in patients with pregnancy rhinitis (1)
      • placental growth hormone
        • after the first trimester of pregnancy the episodic bursts of human growth hormone (hGH) are replaced by a continuous secretion, with rising values of a placental growth hormone variant (PGH)
          • study evidence has shown that serum levels of PGH were significantly higher in the pregnancy rhinitis group throughout pregnancy
          • a 'hormonal rhinitis' has been proposed to occur in acromegaly - PGH may stimulate mucosal growth in a similar way and thereby induce pregnancy rhinitis (1)
    • smoking is a risk factor (2)
      • howevere maternal age, parity, and gender of the child are not associated with increased risk
      • a history of seasonal allergy such as hayfever, asthma, and month of conception have not been found to have a statistically significant impact on incidence of pregnancy rhinitis
    • vasomotor rhinitis, an imbalance in autonomic nervous control of nasal mucosal smooth muscle blood vessels, has also been offered as an aetiology and remains in consideration as a causative or contributing factor
      • given that either oestrogen or emotional stress can initiate vasomotor rhinitis, a synergistic effect is possible, particularly when there is underlying allergic rhinitis

Reference:

• 1) Ellegård EK.Special considerations in the treatment of pregnancy rhinitis.Womens Health (Lond Engl). 2005 Jul;1(1):105-14.
• 2) Ellegard, EK et al. Serum level of placental growth hormone is raised in pregnancy rhinitis, Archives of Otolaryngology and Health and Neck Surgery 1998; 124:439-443
• 3) Ellegard, EK, Karlsson, G.IgE-mediated reactions and hyperreactivity in pregnancy rhinitis. Archives of Otolaryngology and Head and Neck Surgery 1999; 121:1121-1125
• 4) Incaudo, G.A.Diagnosis and treatment of rhinitis during pregnancy and lactation. Clinical Review Allergy 1987; 5(4): 325-337.