Intraocular Pressure across Pregnancy and Postpartum: Trimester-Resolved Physiology, Normative Ranges and Clinical Interpretation

Abstract

Pregnancy is characterized by changes in maternal hormone levels which are needed for proper development of fetus and normal delivery at term. The physiological effects of these hormones are not confined to the reproductive system and affect other organs including eye and its adnexae. Intraocular pressure and tear production are usually decreased in pregnancy. Pregnancy produces coordinated endocrine, cardiovascular, and connective-tissue adaptations that measurably influence intraocular pressure (IOP) and the reliability of common tonometry methods. For clinicians, the key challenge is not simply recognizing that IOP often falls in later gestation, but interpreting trimester-resolved values against shifting corneal biomechanics, physiologic changes in aqueous humor outflow, and the clinical context of pre-existing glaucoma or pregnancy-associated hypertensive and metabolic disorders. This review synthesizes contemporary evidence on IOP trajectories across pregnancy and postpartum, emphasizes mechanisms that plausibly underlie these patterns, and proposes practical “normative” interpretive bands that incorporate both population trends and measurement caveats. Across cohorts and meta-analytic evidence, IOP tends to be similar to non-pregnant baseline in the first trimester, declines modestly in the second trimester, and reaches its lowest levels in the third trimester. Postpartum, IOP generally rebounds toward pre-pregnancy values over weeks to months, though the time course varies by study design and measurement technique. Because central corneal thickness and corneal viscoelasticity may change during gestation, apparent IOP can be biased depending on the instrument used, the time of day, and the patient’s ocular surface status. These physiologic shifts have direct implications for monitoring pregnant and breastfeeding patients with glaucoma: a “reassuring” low IOP may partially reflect pregnancy physiology or altered biomechanics rather than true disease stability, while unexpectedly high or rising IOP warrants careful reassessment for secondary contributors (including corticosteroid exposure) and for pregnancy-related systemic disease. Future progress depends on larger longitudinal studies with standardized timing, device-consistent tonometry, and integrated corneal and systemic metrics to improve normative interpretation and strengthen guidance for higher-risk pregnancies and glaucoma management.