ENT registrar Dr SARA TIMMS and British otolaryngologist Dr EMMA STAPLETON undertook a systematic review to evaluate the effect of pregnancy and pregnancy syndromes on the function of the inner ear. DR TIMMS explains.
By Dr Sara Timms
The inner ear is a complex organ responsible for the conversion of mechanical sound, head position and movement stimuli into electrical signals. It depends on a fine balance of electrolyte and fluid content in the endolymph and perilymph, as well as correctly functioning sensory hair cells.
Research has established that hearing thresholds fluctuate during the menstrual cycle, a pattern which suggests that circulating oestrogen is protective for the inner ear. Vestibular function similarly shows subtle hormonal cycle variability.
In pregnancy, persistent high circulating levels of oestrogen and progesterone lead to much greater physiological changes than those of the menstrual cycle. Cardiac output and circulating volume increase, haemodilution occurs, a thrombotic state develops, and the immune system adapts to become ‘tolerant’ of the developing foetus.
Sensorineural hearing loss and vestibular loss of function caused by trauma, ototoxicity and ageing are understood to be irreversible, whereas other inner ear conditions demonstrate a degree of reversibility.
Pregnancy, with its physiological changes that are reversed post-partum, offers insight into the reversibility of vestibulocochlear dysfunction.
We performed a systematic review, published in the Journal of Laryngology and Otology online on 1 October 2025, to evaluate the effect of pregnancy and pregnancy syndromes on the function of the inner ear. The initial searches identified 341 articles, of which 69 were included in the final analysis.
Of the 69 articles reviewed, 37 contained original research, 29 of which were prospective studies of an observational nature and eight were retrospective reviews. There were no interventional randomised controlled trials, but many observational studies included matched controls. The remaining 32 articles included case series, case studies and reviews.
We reviewed the published work in two categories: those that assessed the effects of normal pregnancy on the inner ear, and those that considered the effect of pregnancy syndromes such as gestational diabetes and preeclampsia.
NORMAL PREGNANCY – HEARING
Three studies reported a statistically significant but subtle hearing loss in pregnancy, particularly in the lower frequencies and in the third trimester of pregnancy. These studies all suggested that this subclinical hearing loss is reversible after delivery.
A small study with 100 participants tested the normal otoacoustic emissions produced by a healthy cochlea. It found them to be absent in 4% of non-pregnant individuals, but in 26% of pregnant women. Another study found a higher incidence of tinnitus in low-risk pregnancy than in non-pregnant controls.
Many studies investigated sudden sensorineural hearing loss (SSNHL) in pregnancy, largely from the perspective of establishing safe treatment guidelines, for example the use of intratympanic steroids. In large whole-population analyses from Taiwan and South Korea, it was found that SSNHL occurs less commonly in pregnancy than in the general population.
NORMAL PREGNANCY – BALANCE
Several observational studies found changes in vestibular function test results in pregnancy, such as reduced gain on the video head impulse test (VHIT) and abnormalities in the vestibular evoked myogenic potentials (VEMPs), particularly in the first trimester.
Vestibular migraine was a common cause of dizziness in pregnancy in one study, a symptom that might wrongly be attributed to ‘normal’ pregnancy nausea. This group of studies raises the possibility that women with significant nausea and vomiting in pregnancy, including hyperemesis gravidarum, may have underlying undiagnosed vestibular pathology.
Supporting this hypothesis, it was found that a history of motion sickness or migraine is more common in those who experience nausea in pregnancy.
PREGNANCY SYNDROMES
Three studies found a statistically significant worsening in hearing thresholds in women with pre-eclampsia compared with pregnant women without pre-eclampsia. One of these studies repeated the assessment after delivery and found the changes to persist, which may be due to the permanent microangiopathy (damage to small blood vessels) caused by the condition.
Similarly, patients with gestational diabetes had significantly worse pure tone thresholds in the higher frequencies (8 kHz to 14 kHz) when compared with pregnant controls, a finding that did not normalise postpartum.
Conclusion
Despite the heterogeneity of the literature, the hearing practitioner can draw several valuable conclusions from this review. The inner ear is sensitive to physiological changes that occur in pregnancy which can affect hearing and balance.
Reasons for this may include altered electrolyte balance in endolymph and perilymph, hypercoagulability affecting small inner ear vessels, or direct effects of pregnancy hormones.
In pregnancy syndromes such as pre-eclampsia these changes may be permanent due to microvascular ischaemia. It is important to take a thorough history, including motion sickness, and consider vestibular diagnoses in a patient presenting with balance symptoms in pregnancy.
About the author: Dr Sara Timms is an ENT registrar training in Manchester, UK who has an interest in otology and hearing implants. She is currently undertaking the Graham Fraser Otology Fellowship in Sydney working with Professor Catherine Birman OAM in the University of Sydney and department members of the Royal Prince Alfred Hospital, Children’s Hospital at Westmead and Nextsense Cochlear Implant Program.
