Seeing stars, flashing lights, or flickering spots during pregnancy usually traces back to one of several causes, ranging from harmless changes in the eye itself to potentially dangerous conditions like preeclampsia. Pregnancy triggers a cascade of cardiovascular, hormonal, and metabolic shifts that can alter how your eyes function, sometimes producing brief visual disturbances that feel alarming but resolve on their own. The challenge is distinguishing the benign episodes from the ones that demand urgent medical attention, because visual symptoms are one of the earliest red flags for some of the most serious pregnancy complications.
How Pregnancy Physically Reshapes Your Eyes
Your body retains more fluid during pregnancy, your blood volume climbs substantially, and hormonal changes affect tissues throughout the body. Your eyes are no exception. One well-documented shift is a drop in intraocular pressure, the fluid pressure inside the eyeball. A cross-sectional study of pregnant women found that pressure in both eyes was significantly higher in the first trimester than in the third, with values steadily declining as pregnancy progressed and rebounding after delivery.1PubMed Central. Changes of intraocular pressure in different trimesters of pregnancy among Syrian refugees in Turkey: A cross-sectional study A separate study confirmed this pattern, finding a significant decrease in eye pressure during the third trimester compared to non-pregnant controls, with no notable change in the first and second trimesters.2PubMed Central. Pregnancy-induced ocular changes: impacts on intraocular pressure, the cornea, and the anterior chamber
Another change happens deeper in the eye, in a layer of blood vessels called the choroid that feeds the retina. Increased blood volume and lower vascular resistance during pregnancy cause this layer to thicken temporarily. Researchers attribute the thickening to enhanced blood flow and estrogen-driven widening of blood vessels, which together increase perfusion through the choroid, especially around mid-pregnancy.3Scientific Reports. Evaluation of longitudinal changes in choroidal thickness during pregnancy and postpartum using widefield swept-source optical coherence tomography The water retention and circulatory changes of pregnancy have also been proposed as drivers of this thickening.4PubMed Central. Evaluation of Choroidal Thickness during Pregnancy and Postpartum: A Longitudinal Study These shifts are usually temporary and reverse after delivery, but they can contribute to subtle visual changes like mild blurriness, light sensitivity, or occasional flickering in your peripheral vision.
Corneal thickness and curvature can change too, which is why eye doctors often recommend waiting until after pregnancy and breastfeeding to update a glasses or contact lens prescription. None of these physiological changes are dangerous on their own. They are the eye’s response to a body that is temporarily running a different circulatory and hormonal program. But they form an important backdrop: your eyes are already in a slightly altered state, which means additional stressors during pregnancy can push visual symptoms further.
Preeclampsia and Retinal Vasospasm
This is the cause your care provider is most concerned about when you mention visual changes. Preeclampsia, a condition marked by high blood pressure and organ stress that develops after about 20 weeks of pregnancy, can directly affect the blood vessels feeding the retina. When blood pressure spikes, the small arteries in the retina constrict in a phenomenon called vasospasm. Researchers have found a significant relationship between a reduced ratio of retinal arteries to veins and preeclampsia, interpreting it as evidence of vasospasm and increased resistance to blood flow in the retina’s vessels.5Saudi Journal of Ophthalmology. The eye and visual system in the preeclampsia/eclampsia syndrome: What to expect?
A case study using Doppler imaging of the eye’s blood flow during a visual disturbance episode in a preeclamptic patient illustrated this process directly. During the episode, blood velocity through the central retinal artery was altered, and resistance was elevated. Once symptoms resolved, blood flow patterns returned closer to normal. The researchers concluded that visual disturbances in preeclampsia are linked to retinal artery vasospasm and temporary loss of blood supply to parts of the retina.6American Journal of Obstetrics and Gynecology. Retinal vasospasm associated with visual disturbance in preeclampsia: Color flow Doppler findings Reduced blood supply to the retina is what produces the sensation of stars, sparkles, or flashing lights. The retina is sending distorted signals because it is briefly not receiving enough oxygen.
In more severe cases, preeclampsia and eclampsia can cause damage to deeper layers of the eye. Research has found that the rate of retinal pigment lesions and small fluid buildups under the retina, both signs of reduced blood flow through the choroid, is high in patients with severe preeclampsia and eclampsia.7PubMed. Retinal pigment epithelial lesions associated with choroidal ischemia in preeclampsia The reassuring aspect is that these changes are generally transient, resolving after blood pressure is brought under control and the pregnancy is delivered. But they underscore why any new visual symptom in the second half of pregnancy should be taken seriously and reported promptly.
When the Brain Gets Involved
Sometimes the problem isn’t in the eye at all. It is in the brain’s visual processing centers, particularly the occipital lobes at the back of the head. A condition called posterior reversible encephalopathy syndrome, or PRES, can develop in women with eclampsia, the seizure-producing stage of preeclampsia. In PRES, severely elevated blood pressure overwhelms the brain’s ability to regulate its own blood flow, and fluid leaks into the brain tissue, producing swelling.
Imaging studies of women with eclampsia-related PRES typically show symmetric swelling in the parietal and occipital regions of the brain. One case series documented this pattern on MRI, finding that the swelling represented fluid accumulation in the tissue rather than permanent cell damage.8PubMed Central. Cortical visual loss in posterior reversible encephalopathy syndrome in late postpartum eclampsia: Case series Because the occipital lobe is where visual information is processed, swelling there can produce dramatic symptoms: severe blurring, tunnel vision, light flashes, and sometimes temporary cortical blindness, where the eyes themselves are fine but the brain cannot interpret what they are seeing. A separate study confirmed that blurred vision and cortical blindness are among the most common visual complaints in eclampsia-related PRES.9Indian Journal of Clinical and Experimental Ophthalmology. A study of posterior reversible encephalopathy syndrome as a cause of sudden transient vision loss during pregnancy
The “reversible” in the name is important. When treated quickly, typically by controlling blood pressure and delivering the baby, the brain swelling resolves and vision returns to normal. Delays in treatment can lead to lasting damage, which is one reason hospitals monitor postpartum women closely for a day or two after delivery if they had preeclampsia or eclampsia.
A less dramatic but still significant brain-related cause of visual symptoms in pregnancy is raised pressure inside the skull without a tumor or other structural cause, sometimes called idiopathic intracranial hypertension. The increased fluid retention and weight gain of pregnancy can worsen this condition in women predisposed to it. Symptoms include headaches, ringing in the ears, and visual changes such as dimming or brief blackouts. In one documented case, a pregnant woman with severe headaches and worsening vision was diagnosed with this condition; her symptoms resolved after delivery.10PubMed Central. Idiopathic Intracranial Hypertension in Pregnancy This condition is much rarer than preeclampsia, but it is worth knowing about because it can mimic some of the same visual symptoms.
Blood Sugar Drops and Visual Disturbances
Pregnancy increases your body’s metabolic demands and changes how you process sugar. Insulin resistance rises, blood sugar can swing more dramatically, and nausea or food aversions in early pregnancy can make it hard to eat enough. If your blood sugar drops too low, your eyes and brain feel it quickly.
A study of patients with hypoglycemia found that visual symptoms were surprisingly common during low-sugar episodes. Blurred vision was the most frequently reported complaint, affecting roughly three-quarters of participants. Dimness of vision appeared in about 45%, dark spots in about 37%, and a central dark area in about a third. More extreme symptoms like double vision or temporary complete loss of sight were less common but still documented. The vast majority of those monitored with continuous glucose sensors had blood sugar below 60 mg/dL when their visual symptoms occurred.11AACE Clinical Case Reports. Visual Symptoms During Hypoglycemia: A Case Series
That study was not specific to pregnant women, but the relevance is clear. Pregnancy is one of the most common situations in which otherwise healthy people experience significant blood sugar drops, especially if meals are spaced too far apart, if morning sickness limits intake, or if gestational diabetes is being managed with insulin. If you notice stars or dark spots consistently when you have not eaten in a while, or if they resolve quickly after a snack, low blood sugar is a strong suspect. Keeping regular meals and having easy-to-grab snacks available can often prevent these episodes.
How Retinal Problems Produce Flashing Lights
Not all flashes during pregnancy trace back to blood pressure, the brain, or blood sugar. Sometimes the issue is mechanical. The vitreous, the gel-like substance filling the inside of the eye, can tug on the retina as it shifts or shrinks, and that traction fires off light signals the brain interprets as flashes or stars. This happens more commonly with age, but pregnancy-related fluid shifts and hormonal changes can occasionally trigger similar events.
Research into the characteristics of these flashes found that the pattern and location matter. In people with a simple vitreous detachment, a benign condition, the flashes were almost always in the outer (temporal) part of the visual field, lasted only seconds, and appeared as vertically oriented streaks. When the flashes appeared in other quadrants or had an oblique or horizontal orientation, they were much more likely to signal a retinal tear or detachment, a condition that requires urgent surgical treatment.12Ophthalmic and Physiological Optics. Discriminate characteristics of photopsia in posterior vitreous detachment, retinal tears and retinal detachment
Retinal detachment during pregnancy is uncommon, but it does happen, and the visual disturbances from it can be mistaken for the other causes described above. A key distinguishing feature is that retinal flashes tend to be very brief, arc-like, and often accompany a shower of new floaters or a curtain-like shadow spreading across part of your vision. If flashes come with a sudden increase in floaters or any loss of peripheral vision, that warrants an urgent trip to an eye doctor, regardless of what is going on with your blood pressure or blood sugar.
Signs That Need Immediate Attention
Given the range of possible causes, from harmless to life-threatening, it helps to know which features of visual disturbance should send you to the phone. Some context matters more than the stars themselves:
- Persistent flashes or spots: Brief, occasional sparkles that happen once and resolve are less concerning than episodes that last minutes, recur within hours, or get progressively worse.
- Accompanying headache: A severe headache that does not respond to normal remedies, especially in the second half of pregnancy, paired with visual changes is a classic warning pattern for preeclampsia.
- Swelling and upper belly pain: Visual symptoms alongside sudden swelling in the face or hands, or pain under the right rib cage, raise the urgency further.
- Loss of a visual field: If part of your vision goes dark or a shadow creeps across one eye, this could indicate a retinal detachment or cortical involvement and needs same-day evaluation.
- Symptoms after 20 weeks: The same visual disturbance that is almost certainly benign at 10 weeks carries a different risk profile at 30 weeks, because preeclampsia becomes a possibility in the second half of pregnancy.
Your care team would rather hear about visual symptoms that turn out to be nothing than miss an early warning. A quick blood pressure check and urine test can rule out or catch preeclampsia in a single visit, and that simple screening can be the difference between a managed condition and an emergency.
The Emotional Weight of Preeclampsia Symptoms
Something that rarely gets discussed alongside the physical symptoms is how stressful the experience can be. Women dealing with preeclampsia are not just managing a medical condition; they are often grappling with significant anxiety, sleep disruption, and psychological distress. A study comparing women with severe preeclampsia to those with mild forms and healthy controls found that women with the most severe disease had markedly higher scores for anxiety, depression, and insomnia.13PubMed. Investigation of maternal psychopathological symptoms, dream anxiety and insomnia in preeclampsia They also experienced more disturbing dreams and greater overall psychological distress.
This matters for the visual-symptoms question because anxiety and poor sleep can themselves amplify visual disturbances. Fatigue makes you more sensitive to light flashes and floaters you might otherwise ignore, and the hypervigilance that comes with worrying about a high-risk pregnancy means you are more likely to notice subtle visual events that were happening all along. None of this means the symptoms are imagined. It means the experience exists on a feedback loop: physical symptoms increase anxiety, anxiety increases awareness of physical symptoms, and sleep deprivation lowers the threshold for both. Acknowledging the psychological dimension is not a way of dismissing the visual complaints. It is a reason to address the whole picture, including mental health support, when managing a complicated pregnancy.
Why Your Prescription Might Feel Off
Separate from the dramatic symptoms, many pregnant women notice that their glasses or contacts just do not seem right anymore. This is a milder consequence of the same physiological changes discussed earlier. The fluid retention that thickens the choroid also affects the cornea, subtly altering its shape and thickness. Combined with the drop in eye pressure, these shifts can temporarily change your refractive error, making your current prescription slightly too strong or too weak.
The standard advice from eye care professionals is to avoid getting a new prescription for glasses or contacts during pregnancy and for several weeks after delivery, because the changes are temporary. Once hormone levels normalize and fluid balance returns to its pre-pregnancy state, your vision typically drifts back. If the change is dramatic enough to affect daily function, disposable contacts in a temporary prescription or a cheap pair of readers can bridge the gap without committing to an expensive new prescription that will be wrong again in a few months.
One situation where the prescription change is not benign: if your vision deteriorates rapidly, especially if one eye is much worse than the other, this can indicate fluid accumulation under the retina or the early stages of retinal detachment, both of which occur at higher rates in preeclampsia. A slow, symmetric drift over weeks is typical of normal pregnancy changes. A sudden, asymmetric shift is not.