This article was medically reviewed by Kate Davies RN, BSc (Hons), FP Cert, Vice President Medical Women’s Health & Longevity at Ultrahuman.
Preeclampsia is a serious pregnancy complication thataffects 2-8% of pregnancies globally and is one of the leading causes of maternal and perinatal mortality worldwide. The early warning signs include severe headaches, vision changes, sudden swelling of the face or hands, upper abdominal pain, sudden weight gain, and elevated blood pressure. If you’re pregnant and experience any of these, seek medical care promptly — do not wait for symptoms to worsen.
Preeclampsia is defined by new-onset high blood pressure (≥140/90 mmHg) after 20 weeks of pregnancy, typically accompanied by signs of organ damage such as protein in the urine, kidney or liver dysfunction, low platelets, neurological symptoms, or impaired placental function (ACOG Practice Bulletin 222, Obstet Gynecol 2020, PMID 32443079). It can also develop postpartum (the period after childbirth, typically the first 6-8 weeks), with cases sometimes appearing up to six weeks after delivery.
This guide walks through the definition and timing of preeclampsia, the specific warning signs to know, who is at elevated risk, what the prevention evidence supports (most notably low-dose aspirin), how diagnosis and treatment work, what wearables can and cannot tell you, and the symptoms that warrant calling your provider right away.
What preeclampsia is
Preeclampsia is high blood pressure that develops during pregnancy, usually after the 20th week of pregnancy, alongside signs that one or more organs are under strain. It typically arises from problems with how the placenta develops in early pregnancy, which then affects the mother’s blood vessels and organs. The condition can range from mild to severe, with severe forms threatening both maternal and fetal health.
The core diagnostic criteria are new-onset high blood pressure plus at least one of the following:
- Protein in the urine (medically called proteinuria) — ≥300 mg in a 24-hour urine collection or a urine protein-to-creatinine ratio of ≥0.3
- Low platelet count (thrombocytopenia) — below 100,000 per microliter
- Kidney strain — rising creatinine or reduced urine output (medically called oliguria)
- Liver dysfunction — elevated liver enzymes and/or severe pain under the right ribs
- Fluid in the lungs (pulmonary edema)
- New brain or vision symptoms — severe headache, vision changes (blurriness, spots, flashing lights), or seizures
Without the additional organ-damage criteria, the diagnosis is gestational hypertension rather than preeclampsia. With seizures, the condition becomes eclampsia, which is a medical emergency. Preeclampsia is treated as a serious condition because progression can be rapid; in some women, mild preeclampsia escalates to severe preeclampsia or eclampsia within hours.
Early warning signs and symptoms to know
Many women with preeclampsia have no obvious symptoms in the early stages, which is why blood pressure and urine checks at prenatal visits are essential. When symptoms do appear (per the ACOG Practice Bulletin 222 guideline), the most common include:
- Severe or persistent headache that doesn’t improve with rest or hydration. Headaches that are unlike your usual headaches (different in character, intensity, or location) are particularly concerning.
- Vision changes. Blurred vision, flashing lights, spots in vision, temporary vision loss, or sensitivity to light. These reflect the effect of preeclampsia on cerebral blood flow.
- Upper abdominal pain, especially under the ribs on the right side. This reflects liver involvement (HELLP syndrome, a severe variant of preeclampsia).
- Sudden swelling (edema) of the face, around the eyes, or in the hands. Pregnancy-related ankle swelling is common; rapid, severe, or facial swelling is not normal.
- Sudden, rapid weight gain in the second half of pregnancy may reflect fluid retention from worsening vascular dysfunction. Patient-education guidance from obstetric organizations commonly flags weight gain of more than 2-3 pounds in a week as worth a same-day call to your provider, though this is a warning sign for evaluation rather than a formal diagnostic criterion.
- Shortness of breath at rest or lying down, which can reflect pulmonary edema or cardiac strain.
- Nausea or vomiting developing in the second half of pregnancy (after the typical first-trimester morning sickness has resolved).
- Decreased fetal movement — fewer than usual fetal kicks or activity. The placenta may not be delivering adequate blood flow.
- Elevated blood pressure documented on home or clinic monitoring, especially readings ≥140/90 mmHg on two occasions at least 4 hours apart, or any reading ≥160/110 mmHg.
Important: These symptoms can appear individually or together, and severity can change quickly. Do not wait to see if they improve. If you’re pregnant and experiencing any of these signs, contact your prenatal care provider immediately. For severe headache, vision changes, abdominal pain, shortness of breath, decreased fetal movement, or any blood pressure reading of 160/110 mmHg or greater, seek emergency care.
These symptoms are warning signs that warrant evaluation, not the formal diagnostic criteria. The diagnosis of preeclampsia is established by blood pressure measurement and (when BP is elevated) laboratory testing for protein in urine and signs of organ involvement, as listed in the previous section.
Who’s at higher risk
Knowing your individual risk helps with prevention and monitoring discussions with your obstetric provider. The most well-established risk factors are:
- First pregnancy (nulliparity) — preeclampsia is most common in first pregnancies.
- Previous preeclampsia — a prior affected pregnancy substantially raises risk in subsequent pregnancies.
- Chronic hypertension or pre-existing kidney disease.
- Pre-existing diabetes (type 1 or type 2). Gestational diabetes is a separate risk profile that develops during pregnancy and is managed under different guidelines.
- Autoimmune conditions (lupus, antiphospholipid syndrome).
- Multiple pregnancy (twins, triplets).
- Maternal age over 35.
- Obesity (BMI ≥30 before pregnancy).
- Family history of preeclampsia in a first-degree relative.
- Pregnancies conceived via assisted reproductive technology (IVF, donor egg).
- A long gap between pregnancies (greater than 10 years) or a first pregnancy with a new partner.
Genetics and family history play a real part in individual preeclampsia risk. Research is ongoing in the development of genetic risk scoring tools that may eventually help identify higher-risk pregnancies earlier, though these remain research-stage rather than routine clinical care (Honigberg et al., Nat Med 2023, PMID 37248299).
Your obstetric provider should review your specific risk profile in early pregnancy and tailor monitoring accordingly. Women with multiple risk factors may have more frequent blood pressure and urine checks.
What the prevention evidence shows
The strongest evidence-based prevention for preeclampsia is low-dose aspirin for women at elevated risk. The ASPRE trial published in The New England Journal of Medicine randomized 1,776 women screened as high risk of preterm preeclampsia to receive 150 mg of aspirin daily versus placebo from 11-14 weeks until 36 weeks of pregnancy. The aspirin group had a 62% reduction in preterm preeclampsia (Rolnik et al., N Engl J Med 2017, PMID 28657417).
The US Preventive Services Task Force in JAMA issues a separate practical US recommendation: low-dose aspirin (81 mg/day) after 12 weeks of pregnancy for women at high risk of preeclampsia, with a Grade B recommendation (USPSTF, JAMA 2021, PMID 34581729). ACOG aligns with the USPSTF 81 mg recommendation in US practice. The decision to start aspirin is one your obstetric provider makes based on your specific risk profile; it is not a self-prescribing decision.
Important: Do not start low-dose aspirin in pregnancy without consulting your obstetric provider. Aspirin in pregnancy is a prescription-level decision involving individual risk assessment, and the recommendation does not apply to every pregnant person.
Other evidence-supported strategies that may modestly reduce risk include:
- Calcium supplementation. Some evidence supports calcium supplementation in pregnancies with documented low dietary calcium intake, mostly in low-resource settings; this is a clinical decision for your obstetric provider.
- Regular prenatal care — attending all scheduled visits substantially improves the chance of catching preeclampsia early when it’s most manageable.
- Managing pre-existing conditions (hypertension, diabetes, autoimmune disease) carefully through pregnancy in coordination with specialists.
Lifestyle factors (diet quality, exercise, sleep) support overall pregnancy health, but no specific diet or exercise program has been shown to prevent preeclampsia in randomized clinical trials to date. Lifestyle changes should be discussed with your obstetric provider in the context of your overall pregnancy care plan.
How preeclampsia is diagnosed and treated
Diagnosis combines repeated blood pressure measurements (two readings ≥140/90 mmHg at least 4 hours apart after 20 weeks of pregnancy), urine analysis for protein, blood tests for platelets, kidney function, and liver enzymes, and clinical assessment for symptoms and fetal wellbeing.
Management depends on severity, gestational age, and maternal and fetal status:
- Mild preeclampsia near term may be managed with close monitoring, blood pressure control, and planned delivery.
- Severe preeclampsia or preeclampsia with severe features typically requires hospitalization, intravenous magnesium sulfate to prevent seizures, blood pressure medications, and (depending on gestational age and severity) timely delivery.
- HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets) is a severe variant requiring immediate hospitalization and often urgent delivery.
- Postpartum preeclampsia — which can develop up to six weeks after delivery — is managed similarly with blood pressure monitoring, magnesium if needed, and continued obstetric follow-up.
Delivery is the only definitive treatment. The timing is balanced between maternal risk (worsening preeclampsia) and fetal risk (prematurity). Decisions about timing are made by the obstetric team based on individual clinical picture.
What wearables can and can’t tell you in pregnancy
During pregnancy, wearable data can flag general physiological shifts — a rising resting heart rate, declining heart rate variability, sleep disruption, or temperature changes — that may prompt earlier conversations with your prenatal provider. They cannot diagnose preeclampsia or replace the clinical workup (blood pressure measurement, urine protein, blood tests, fetal assessment) that establishes the diagnosis.
Where a wearable can add value during pregnancy:
- Pattern visibility. Sustained shifts in resting heart rate or HRV that don’t match your typical baseline may justify an earlier prenatal check rather than waiting for the next scheduled visit.
- Sleep tracking. Poor or disrupted sleep is common in late pregnancy but can also accompany worsening preeclampsia.
- Daily wellness context. Combined with your symptom awareness, wearable trends can be one input in your conversation with your obstetric provider.
What a wearable cannot do:
- Measure your blood pressure.
- Detect protein in your urine.
- Monitor fetal movements.
- Diagnose preeclampsia or any other pregnancy complication.
- Replace any prenatal visit, blood pressure check, or clinical assessment.
Methodology note — wearable rings, including the Ultrahuman Ring AIR and Ring PRO, track nocturnal vitals (resting heart rate, heart rate variability, skin temperature, sleep stages, stress rhythm) that can shift during pregnancy and during developing complications. Wearables do not measure blood pressure or urine protein, which are the diagnostic criteria for preeclampsia. They are not preeclampsia screening tools and do not replace prenatal blood pressure and urine checks.
When to call your provider immediately
Pregnancy creates an evolving risk profile. The following symptoms warrant immediate contact with your obstetric provider or emergency care, regardless of how many weeks you are:
- Severe headache that doesn’t improve with rest, hydration, or routine pain relief
- Vision changes (blurred vision, spots, flashing lights, vision loss)
- Upper abdominal pain, especially under the right ribs
- Severe nausea or vomiting appearing in the second or third trimester
- Sudden, severe swelling of the face, hands, or feet
- Sudden weight gain of more than 2-3 pounds in a week
- Shortness of breath at rest or when lying down
- Decreased or absent fetal movement
- Blood pressure reading ≥160/110 mmHg — emergency, regardless of symptoms
- Any blood pressure reading ≥140/90 mmHg combined with any other warning symptom
- Bleeding from the vagina or signs of placental abruption
If you cannot reach your provider, go to the nearest emergency department. Preeclampsia is treatable but progression can be rapid, and early intervention substantially improves outcomes for both mother and baby.
This article is for informational purposes and is not medical advice. Preeclampsia is a serious medical condition; if you are pregnant and experience any of the warning signs described, contact your obstetric provider or emergency services immediately. Disclosure: Ultrahuman sells the Ring AIR and Ring PRO, which track nocturnal vitals (resting heart rate, HRV, skin temperature, sleep stages) using PPG sensing. These wearables are not diagnostic tools, do not measure blood pressure, and do not replace clinical assessment or prenatal care.
