Gestational hypertension is diagnosed when blood pressure reaches 140/90 mmHg or higher on two separate readings taken at least four hours apart, after 20 weeks of pregnancy, in someone who previously had normal blood pressure. The diagnosis also requires that there be no protein in the urine and no signs of organ damage, which would instead point to preeclampsia.
The Blood Pressure Thresholds
The specific cutoff is a systolic reading (the top number) of 140 mmHg or higher, or a diastolic reading (the bottom number) of 90 mmHg or higher. A single high reading isn’t enough. Your provider needs to see elevated numbers on at least two occasions, separated by a minimum of four hours, to confirm the diagnosis. This repeat measurement rules out temporary spikes caused by stress, rushing to an appointment, or the “white coat” effect some people experience in medical settings.
The 20-week mark is critical for classification. High blood pressure detected before 20 weeks is considered chronic hypertension, meaning it likely existed before pregnancy. Blood pressure that rises after 20 weeks in someone with no prior history is what gets classified as gestational hypertension. This distinction matters because the two conditions carry different risk profiles and are managed differently.
What Sets It Apart From Preeclampsia
The key difference between gestational hypertension and preeclampsia is organ involvement. Gestational hypertension is elevated blood pressure alone. Once protein shows up in the urine, or there are signs of damage to the liver, kidneys, or blood cells, the diagnosis gets upgraded to preeclampsia. About 17% of women diagnosed with gestational hypertension eventually progress to preeclampsia, which is why the diagnosis triggers ongoing monitoring rather than a one-time assessment.
Lab Tests Used in the Workup
When your blood pressure first reads high, your provider will order blood and urine tests. These aren’t used to diagnose gestational hypertension itself (that’s done with the blood pressure readings), but to rule out preeclampsia and establish a baseline for future comparison. The blood work typically includes a complete blood count with platelet count, liver enzyme levels, and a measure of kidney function. Your provider is specifically checking whether platelets have dropped below the normal range of 150,000 to 400,000 and whether liver enzymes have started climbing.
A urine test checks for protein, which is one of the hallmark signs of preeclampsia. Some providers collect a single sample; others may request a 24-hour urine collection for a more precise measurement. You may hear your care team refer to this panel of tests as “PIH labs” or a “preeclampsia panel.” These labs are typically repeated if your blood pressure continues to rise or you develop new symptoms like headaches, vision changes, or upper abdominal pain, since those could signal progression.
Fetal Monitoring After Diagnosis
A gestational hypertension diagnosis triggers fetal surveillance because the condition increases the risk of complications for the baby, including restricted growth and, in rare cases, stillbirth. The most common tool is the nonstress test, which monitors your baby’s heart rate for about 20 minutes using sensors placed on your abdomen. A “reactive” result, meaning the heart rate accelerates at least twice during the monitoring window, with each acceleration rising 15 beats per minute above baseline for at least 15 seconds, is a reassuring sign of fetal well-being.
If the nonstress test doesn’t show enough heart rate accelerations, your provider may move to a biophysical profile. This combines the heart rate monitoring with an ultrasound that evaluates four additional factors: the baby’s breathing movements, body movements, muscle tone, and amniotic fluid levels. Together, these five components give a more complete picture of how the baby is doing. Depending on how far along you are and the severity of your blood pressure readings, these tests may be scheduled weekly or more frequently.
What Happens After Delivery
The diagnosis of gestational hypertension is, in a sense, confirmed retroactively. If blood pressure returns to normal within 12 weeks after delivery, the diagnosis stands. If it remains elevated beyond that window, the condition is reclassified as chronic hypertension, meaning pregnancy likely unmasked a blood pressure problem that was already developing. Your provider will continue checking your blood pressure at postpartum visits for this reason, and the 12-week timeline is the standard benchmark used to determine which category you fall into.