According to the World Health Organization (WHO), hypertensive disorders during pregnancy are one of the major causes of maternal mortality and morbidity worldwide.
High blood pressure during pregnancy has become more common over the last few decades. It can put both you and your baby at many potential risks during pregnancy and delivery. However, a healthy outcome can be achieved with good blood pressure control.
How common are hypertensive disorders during pregnancy?
A large survey conducted in the United States by the Centers for Disease Control and Prevention (CDC) showed a substantial rise in hypertensive disorders in pregnant ladies, with cases almost doubling from 1993 to 2014. In the United States, 1 in every 12 to 17 pregnancies among women ages 20-44 is affected by high blood pressure.
According to another international survey, the global incidence of hypertensive disorders in pregnancy increased from 16.3 million cases in 1990 to 18.08 million cases in 2019.
Physiological changes in blood pressure during pregnancy
Blood pressure changes throughout a normal pregnancy, with a fall in the 1st and 2nd trimesters and a rise toward term reaching non-pregnant levels in the 3rd trimester.
So, in a normal pregnancy, blood pressure remains on the lower end of the normal value, which is equal to or less than 120/80 mmHg. The number on the top (120 mmHg) is systolic blood pressure, and the bottom one (80mmHg) is diastolic blood pressure.
How one is diagnosed with hypertension during pregnancy
Currently, the following threshold is accepted by most national bodies and international organizations to define hypertension in pregnancy.
You may be labeled hypertensive during pregnancy if:
- Your systolic blood pressure is greater than or equal to 140mmHg and/or
- Your diastolic blood pressure is greater than or equal to 90mmHg.
These readings should be confirmed by repeated blood pressure measurements at rest over a period of 4-6 hours.
Classification of hypertensive disorders in pregnancy
These are the 4 main types of high blood pressure disorders during pregnancy:
- Gestational hypertension
- Chronic hypertension
- Preeclampsia superimposed on chronic hypertension
Let’s discuss each of them separately.
Preeclampsia is a complicating factor in 2% to 8% of pregnancies worldwide. A clinical diagnosis of preeclampsia is made when you start having elevated blood pressure (equal to or more than 140/90 mmHg) after 20 weeks of pregnancy accompanied by one or more of the systemic manifestations below.
When preeclampsia develops before 34 weeks of gestation, it’s called early-onset preeclampsia. If it happens after 34 weeks, it is known as late-onset preeclampsia.
Signs of preeclampsia
Here are some preeclampsia symptoms:
- Proteinuria (protein in urine)
- Low platelet count
- Hemolysis (breakdown of red blood cells)
- Abnormal liver function tests (LFTs)
- Severe upper abdominal pain
- Severe persistent headache
- Persistent visual disturbances
- Pulmonary edema (accumulation of excessive fluid in lungs, making breathing difficult)
- Placental abruption (premature placental separation)
- Intrauterine growth restriction (IUGR) and/or fetal distress
Hypertension accompanied by proteinuria is considered a hallmark for the diagnosis of preeclampsia, but it can present without proteinuria with any of the above-mentioned systemic features.
Risk factors for preeclampsia
There are many risk factors associated with an increased likelihood of developing preeclampsia. They are as follows:
- First pregnancy
- Multiple pregnancy
- Maternal age more than 35
- Pre-pregnancy body mass index (BMI) of more than 30
- Preeclampsia in previous pregnancies
- Chronic hypertension
- Pre-pregnancy diabetes
- Gestational diabetes
- Kidney disease
- Obstructive sleep apnea (loud snoring and interrupted breathing when something blocks part or all of your upper airway while you sleep).
- Assisted reproductive techniques like in vitro fertilization (IVF)
Although these factors increase your risk of developing preeclampsia, remember that many cases occur in young, healthy women at no apparent risk.
What causes preeclampsia?
This is a condition that only occurs during pregnancy. In preeclampsia, there is some placental dysfunction, which can lead to many problems and affect both you and your baby.
The exact cause of preeclampsia is still unknown. It can affect any pregnancy at any time after 20 weeks of gestation. Obviously, women having risk factors are more prone to develop preeclampsia than those who have no risk factor.
For more information on preeclampsia, check out this article.
Preeclampsia vs. eclampsia
In some cases, women with severe preeclampsia may develop seizures or convulsions during pregnancy or around the time of delivery. This condition is called eclampsia, and it complicates around 0.3% of pregnancies globally.
Eclampsia can result in intracranial bleed, aspiration pneumonia, kidney failure, placental abruption, fetal distress, and even fetal or maternal death. It’s a medical emergency and a potentially life-threatening condition. It is a severe form of preeclampsia.
Eclampsia management includes maternal stabilization with medicines given to lower blood pressure and prevent further fits. This is followed by delivery of the baby regardless of gestational age. Giving birth is the only definitive treatment, so either induction of labor or a cesarean section is carried out. In many cases, a cesarean section is preferred over induction because it leads to immediate delivery, and there is also no risk of a rise in blood pressure as often seen during labor.
2. Gestational hypertension
Gestational hypertension is diagnosed when you develop hypertension after 20 weeks of gestation (without any other systemic findings of preeclampsia, like proteins in the urine). Blood pressure returns to normal within 3 months after childbirth.
Gestational hypertension is considered severe if systolic blood pressure rises up to 160mmHg and/or diastolic blood pressure reaches 110mmHg.
Clinical features of gestational hypertension
Gestational hypertension mostly has no physical symptoms at all and is usually diagnosed when you are found to have high blood pressure during a routine prenatal check-up. That’s why you should not miss these check-ups.
Some women may present with a mild headache. In some, gestational hypertension eventually progresses to preeclampsia and leads to conditions like proteinuria. The chances of developing preeclampsia are higher when gestational hypertension is diagnosed before 32 weeks of pregnancy.
Gestational hypertension near term is associated with little increase in adverse pregnancy outcomes. The earlier the presentation and the more severe the hypertension, the higher the likelihood of complications during pregnancy.
Some women diagnosed with gestational hypertension may end up having chronic hypertension when their blood pressure doesn’t return to normal 3 months after delivery.
3. Chronic hypertension
If a pregnant woman has pre-existing hypertension or is diagnosed with elevated blood pressure before 20 full weeks of gestation, her condition is classified as chronic hypertension.
Approximately 3% to 5% of pregnancies are affected by chronic hypertension. This incidence is rising as more and more women get pregnant at an older age. The prevalence of obesity is another major contributing factor.
It’s advisable to optimize your blood pressure and overall health before conception if you’re already diagnosed with chronic hypertension. There are certain medicines for chronic hypertension management that are contraindicated during pregnancy, so book a pre-pregnancy consultation with your ob-gyn and get your medicines changed before pregnancy.
Types of chronic hypertension
Chronic hypertension is divided into 2 types on the basis of etiology.
- Essential or primary hypertension: This is the most common type of chronic hypertension affecting the adult population. It’s called primary hypertension because there is no identifiable cause of high blood pressure. Essential hypertension is responsible for 90% of cases of chronic hypertension associated with pregnancy.
- Secondary hypertension: When chronic high blood pressure is caused by some underlying medical disorder, it’s classified as secondary hypertension. These medical disorders include kidney diseases, vascular disorders, endocrinological problems, etc.
For the purpose of clinical management, chronic hypertension in pregnancy may also be divided into the following 2 groups:
- Low-risk group: If you have isolated chronic hypertension without any hypertensive end organ damage (damage to eyes, kidneys, heart, etc.) or associated comorbidity (diabetes, high cholesterol level, heart disease, etc.), you are in the low risk category.
- High-risk group: When chronic hypertension is accompanied with end organ damage, associated comorbidity, or superimposed preeclampsia, the patient is in the high risk category, and there are far higher chances of fetal as well as maternal complications.
4. Preeclampsia superimposed on chronic hypertension
Women who already have chronic hypertension are at risk of developing preeclampsia as they cross the 20-week gestation mark. If this happens, it’s called preeclampsia superimposed on chronic hypertension.
According to a medical survey, approximately 43.3% of women who already have chronic hypertension develop superimposed preeclampsia during pregnancy.
What are the risks of hypertension during pregnancy?
There are many potential maternal and fetal risks associated with hypertensive disorders during pregnancy. Usually, maternal and perinatal outcomes are favorable in women with mild gestational hypertension, well-controlled chronic hypertension, and mild late-onset preeclampsia. With proper management, these patients deliver at term without any complications.
However, severe cases of preeclampsia predispose both mom and baby to multiple health risks.
Mothers are at risk of:
- Seizures or convulsions during pregnancy (eclampsia)
- HELLP syndrome (more below)
- Placenta abruption (separation of the placenta from the womb before delivery)
- Organ failure
- Preterm delivery
- Prolonged hospitalization
- In some cases, especially in developing countries, maternal death may also occur, mostly because of delayed or inadequate medical management.
- Preeclampsia during pregnancy is also associated with long-term health risks. Women are at greater risk of developing heart problems, chronic hypertension, kidney diseases, and diabetes later in life.
What is HELLP syndrome?
Severe preeclampsia can also manifest as HELLP syndrome. It is characterized by hemolysis (H), elevated liver enzymes (EL), and low platelets (LP).
This is a syndrome involving the blood and liver. The exact cause of HELLP is unclear. It’s most probably caused by several factors.
Is HELLP syndrome hereditary? Some women may have a genetic predisposition for preeclampsia and related diseases like HELLP.
What are the symptoms of HELLP syndrome? Patients usually present with fatigue, malaise, excessive swelling on the face, hands and feet, blurred vision, nausea, and severe epigastric or right upper abdominal pain.
Just like eclampsia, this is also a life-threatening condition and needs early detection and aggressive medical management. Delivery is the only permanent solution, however; the patient’s condition improves gradually postpartum. You may need to stay in the hospital for a few extra days.
Babies are at risk of:
These babies may also require prolonged neonatal care in hospital.
Management of hypertensive disorders during pregnancy
As hypertension makes for a high-risk pregnancy, you will be monitored closely by your health team to ensure that you can safely carry on with your pregnancy. This may be done on an outpatient basis if you have mild hypertension. In severe cases, patients are admitted for further testing and management.
If you have mild or well-controlled hypertension and everything goes smoothly, there are higher chances that you will deliver at around 37 weeks of gestation. However, if you develop a serious condition, such as severe preeclampsia, delivery is planned after stabilizing your condition.
Usually, symptoms of preeclampsia disappear after delivery, but in severe cases, complications may still occur. Therefore, you may need to stay in hospital for monitoring and continue taking medicines to lower your blood pressure for some time.
When you go home, you will be advised on how frequently you should get your blood pressure checked. You’ll also have a follow-up visit at 6 to 8 weeks. If you’re still on medication to control your blood pressure, you might be referred to a specialist.
What are the chances of hypertension recurring in my next pregnancy?
Overall, there is a 20% chance (1 in 5 women) of hypertensive disorder recurring in your next pregnancy.
However, this risk may increase if you develop preeclampsia early in pregnancy or if it’s associated with serious manifestations, like IUGR.
How to prevent high blood pressure during pregnancy
The exact underlying cause of these hypertensive disorders is still not clearly identified, and there are no specific screening tests available yet that can predict whether you will develop gestational hypertension or preeclampsia during pregnancy.
That’s why complete prevention is not possible, but the following tips may help reduce the risk of developing hypertensive disorders during pregnancy.
- Maintain your pre-pregnancy weight within the normal BMI range. Eat a healthy balanced diet, reduce your salt intake, and stay active.
- If you have chronic hypertension or any other systemic disease, optimize your health beforehand.
- Start taking folic acid supplements before pregnancy because they not only protect your baby from neural tube defects but are also found to have a protective role against preeclampsia.
- Some studies have shown that calcium supplements (when given to a calcium-deficient population) may also lower the risk of developing preeclampsia.
Hypertensive disorders can occur in any pregnancy regardless of the presence of prior risk factor, so all pregnant women should have regular prenatal check-ups. With early diagnosis and an optimal management plan, healthy feto-maternal outcomes can be achieved in most cases.