Pregnancy-induced hypertension (PIH) is high blood pressure that develops for the first time after 20 weeks of pregnancy in someone who previously had normal readings. It’s diagnosed when blood pressure reaches 140/90 mm Hg or higher on two separate occasions. Roughly 10 to 22% of pregnant women worldwide are affected by hypertensive disorders of pregnancy, and that number is expected to climb as maternal age and obesity rates rise.
How PIH Differs From Other Blood Pressure Problems in Pregnancy
Not all high blood pressure during pregnancy is the same. If you had high blood pressure before getting pregnant, or it showed up before the 20-week mark, that’s considered chronic hypertension. PIH, by contrast, appears only in the second half of pregnancy and typically resolves after delivery.
The term people most often confuse with PIH is preeclampsia. Both conditions involve new-onset high blood pressure after 20 weeks, but preeclampsia also causes signs of organ stress, such as protein spilling into the urine, liver problems, or changes in kidney function. That distinction matters because the risks are different. Research comparing the two conditions found that preeclampsia was strongly associated with cesarean delivery, placental abruption, growth-restricted babies, and low Apgar scores at birth. Gestational hypertension, on its own, was primarily linked to an increased risk of preterm birth. However, gestational hypertension can progress to preeclampsia, which is why close monitoring is essential once it’s diagnosed.
What Happens in the Body
During a healthy pregnancy, specialized placental cells called trophoblasts remodel the blood vessels (spiral arteries) that supply the placenta. They widen these arteries so blood flows freely to the growing baby. In PIH, this remodeling is shallow and incomplete. The arteries stay narrow and resistant, reducing blood flow to the placenta. The mother’s cardiovascular system compensates by raising blood pressure to push more blood through those constricted vessels, which is what produces the elevated readings at prenatal visits.
Because the underlying problem is restricted blood flow to the placenta, the baby may not receive enough oxygen and nutrients to grow at a normal rate. This is why PIH can lead to low birth weight or the need for early delivery.
Who Is at Higher Risk
Some women are more likely to develop PIH than others. The risk factors fall into two tiers.
- High-risk factors: a history of preeclampsia, chronic hypertension, type 1 or type 2 diabetes, kidney disease, autoimmune conditions (particularly lupus), and carrying twins or other multiples.
- Moderate-risk factors: first pregnancy, a BMI over 30, being 35 or older at delivery, a gap of more than 10 years between pregnancies, a family history of preeclampsia in a mother or sister, African American race, low socioeconomic status, and a previous pregnancy with poor outcomes.
Conditions that reduce blood flow to the placenta in general, including sleep apnea and clotting disorders, also raise the likelihood. Having multiple moderate-risk factors compounds the overall risk.
Risks for Mother and Baby
For the mother, PIH can lead to preeclampsia, eclampsia (seizures), stroke, placental abruption (the placenta detaching from the uterine wall), and a higher chance of needing labor induction or cesarean delivery. Placental abruption is a medical emergency that can cause heavy bleeding and endanger both mother and baby.
For the baby, the main concerns are preterm birth (before 37 weeks) and low birth weight, defined as under 5 pounds, 8 ounces. When blood pressure stays elevated, the reduced placental blood flow makes it harder for the baby to grow normally, which is often the reason providers decide to deliver early.
How It’s Managed During Pregnancy
There is no way to “cure” PIH while pregnancy continues. Management focuses on keeping blood pressure in a safe range and watching closely for signs that the condition is worsening into preeclampsia. That means more frequent prenatal visits, regular blood pressure checks (sometimes at home), blood tests to monitor kidney and liver function, and ultrasounds to track the baby’s growth.
Current guidelines recommend delivery at 37 weeks of gestation for women with gestational hypertension that hasn’t progressed to preeclampsia with severe features. If the diagnosis comes after 37 weeks, delivery is typically recommended at the time of diagnosis. The reasoning is straightforward: removing the placenta is the only definitive treatment, and by 37 weeks the baby is developed enough that the risks of staying pregnant outweigh the risks of early delivery.
What Happens After Delivery
For most women, blood pressure gradually returns to normal after the baby and placenta are delivered. Gestational hypertension and preeclampsia typically resolve within 12 weeks postpartum, though some women experience elevated readings for several weeks before things settle. Providers usually continue monitoring blood pressure in the early postpartum period and may use short-term medication if readings remain high.
The longer-term picture deserves attention. A large national cohort study published in The Lancet Healthy Longevity found that women who had gestational hypertension faced roughly double the risk of dying from cardiovascular disease later in life compared to women with uncomplicated pregnancies (an adjusted hazard ratio of 2.22). For women who had preeclampsia, the risk was more than three times higher. This doesn’t mean heart disease is inevitable, but it does mean a history of PIH is a meaningful signal. It’s worth treating it as an early warning to stay on top of heart health in the years and decades that follow, through regular blood pressure screening, maintaining a healthy weight, staying physically active, and managing cholesterol.