Cause of low blood pressure during pregnancy

High blood pressure, or hypertension, is associated with problems with fertility in males and pregnancy complications in females, such as premature birth. However, low blood pressure, known as hypotension, can also make it difficult to become pregnant and maintain that pregnancy.

Understanding Blood Pressure

Your blood pressure is recorded as two numbers:

• Systolic blood pressure, which is the top number, indicates how much pressure your blood is exerting against your artery walls when your heart beats.
• Diastolic blood pressure, the bottom number, indicates how much pressure your blood is exerting against your artery walls while your heart is resting between beats.

Low blood pressure occurs when blood pressure is much lower than normal. This means the heart, brain, and other parts of the body do not get enough blood. If your blood pressure is 90/60 mm Hg (millimeters of mercury) or lower, you have low blood pressure.

Low Blood Pressure and Fertility

There isn’t a lot of data showing that low blood pressure has a negative impact on fertility, but low blood pressure may signal an underlying condition that can affect fertility.

One of these conditions is an endocrine disorder that causes a hormonal imbalance when the glands that produce endocrine hormones produce too few or too many.

Some hormones help regulate the growth of an egg within an ovary, the release of the egg into the fallopian tube, and the thickening of the uterine lining for implantation, where the fertilized egg will attach and grow. Any disruption to the hormones can prevent or delay these processes from occurring.

One example is problems with the renin–angiotensin–aldosterone system (RAAS). As part of the endocrine system, the RAAS helps to regulate blood pressure by controlling blood volume and vascular tone in your arteries. It also plays a role in ovulation, implantation, and other reproductive functions.

Conditions that impact the function of the endocrine system, like RAAS dysfunction, could therefore complicate the ovulation process and efforts to conceive.

Other hormonal disorders that have been linked to low blood pressure and infertility include:

• Diabetes
• Thyroid disorders
• Adrenal gland dysfunction

A number of conditions associated with infertility—like diabetes and thyroid disease—are passed down through families. In fact, about half of all cases of infertility are linked to genetic factors.

Low Blood Pressure and Gestation

Low blood pressure can cause problems getting pregnant, but where it becomes more concerning is during pregnancy. Low blood pressure can cause symptoms like:

• Dizziness
• Nausea
• Blurred vision
• Cool, sweaty skin
• Fatigue or weakness
• Shallow breathing

Orthostatic, or postural, hypotension is the most common type of low blood pressure in pregnant people. It happens when you feel faint or dizzy when you stand up or change positions suddenly.

Pregnancy is a major cause of low blood pressure on its own. During the first 24 weeks of pregnancy, it’s common for blood pressure to drop. That's because your body secretes higher levels of certain hormones like progesterone, which help relax the walls of your blood vessels, reducing resistance to blood flow and, in turn, reducing blood pressure.

Low pressure can also be caused or worsened by certain medications, dehydration, stress, and having low blood sugar. Low blood pressure is most common in the first 24 weeks of pregnancy.

Risks

Hypotension can be dangerous during pregnancy for a number of reasons. For one, dizziness increases your risk of fainting and falling, which can cause injury to you and your baby. Untreated hypotension can also cause organ damage since the amount of blood and nutrients delivered throughout your body and to your baby decreases.

Most studies on maternal blood pressure focus on high blood pressure, which causes such serious conditions as preeclampsia, which can lead to organ failure. However, one study estimates that low blood pressure is also dangerous, especially in the third trimester, when it can increase the risk of preterm birth by 150%.

Treatment

How your hypotension is treated depends on what is causing it and what symptoms you are having. Low blood pressure that is not causing any symptoms or complications may not require treatment.

Your doctor will review any medications you are taking to determine if any of them could be causing your low blood pressure. You can also make lifestyle changes that could help reduce symptoms of hypotension like:

• Drinking more water
• Eating smaller meals
• Adjusting your salt intake
• Limiting carbohydrates
• Changing positions slowly when getting up
• Avoiding standing for long periods
• Wearing compression stockings
• Sitting up and taking some deep breaths before you get out of bed

If you are experiencing fainting and falling, your doctor may suggest medications or even hospitalization to help manage your symptoms and ensure the safety of you and your baby.

Concerning Symptoms

There isn't an exact range of concerning measurements for low blood pressure as there is for high blood pressure. Anything lower than 90/60 mm Hg is considered low, and your healthcare provider will diagnose and treat you based on what symptoms you are having rather than the number itself.

If you are fainting and falling, be sure to discuss your condition with a healthcare provider as soon as possible.

Low Blood Pressure and Postpartum

If you have chronic low blood pressure before your pregnancy, you may continue to face this problem after delivery. If you stopped certain medications during your pregnancy, you may be able to resume them postpartum. But talk to your doctor about this first if you plan to breastfeed.

In some cases, complications of delivery can cause new hypotension after your baby is born.

Impact on Recovery

If you experienced a complicated delivery, you may have low blood pressure for a time after your baby is born. This is especially true if you have postpartum hemorrhage. In these cases, your blood volume is depleted, and your blood pressure will drop in response. Your healthcare team may give you blood transfusions and fluids to help increase your blood and fluid volumes.

If you have symptoms of low blood pressure like dizziness after delivery or when you go home from the hospital, talk to your healthcare provider about ways to manage these symptoms to keep you and your baby safe. This may include reviewing your diet, activity level, and water intake.

Sheehan's syndrome is a rare condition that puts you at a higher risk of developing postpartum hemorrhage, hypotension, and difficulties breastfeeding. Sheehan's syndrome is difficult to diagnosis. It requires the care of a specialist. Treatment usually involves replacement of certain hormones.

Breastfeeding

Breastfeeding outcomes can be influenced by a lot of circumstances, including hydration, diet, activity, and hormones. Not a lot of data exist to suggest that low blood pressure negatively affects breastfeeding, but studies have shown that breastfeeding can cause blood pressure to drop during and immediately after nursing sessions.

This could pose a problem for mothers who already have low blood pressure. Talk to your healthcare provider if you are experiencing dizziness or falling after breastfeeding.

Summary

There is not much evidence that shows low blood pressure is linked to fertility issues, but hypotension could be a sign of an underlying condition associated with infertility. Pregnant people are more likely to develop low blood pressure because their bodies produce more of the hormones that dilate the walls of blood vessels, reducing blood pressure within them.

While not much research has shown that low blood pressure can negatively affect the baby, it may cause dizziness in the mother and increase the risk of falling and injury.

A Word From Verywell

Low blood pressure is common in pregnancy, but it doesn't usually lead to the problems that high blood pressure can cause. If you're experiencing symptoms of low blood pressure like dizziness or fainting, your doctor may recommend lifestyle changes that can help control the symptoms and protect you and your baby. Call you doctor immediately if you feel like your blood pressure is low and is causing you to fall or lose consciousness.

Frequently Asked Questions

What is considered low blood pressure during pregnancy?

There isn't a set range of blood pressure readings that are worrisome, but anything below 90/60 mm Hg can be considered low. Treatment will focus on your symptoms rather than the numbers in your blood pressure measurement.

What causes low blood pressure during pregnancy?

Low blood pressure in pregnancy can be caused by natural fluid and hormonal shifts, low blood sugar levels, and dehydration. Orthostatic hypotension—low blood pressure brought on by changes in position—also is common during pregnancy.

How do you treat low blood pressure during pregnancy?

Your doctor may not need to treat your low blood pressure unless it is really low or you have symptoms like fainting or falling, which can increase the risk of injury for you and your baby. Generally, treatment involves rest, taking care when sitting up or standing, drinking more water, and making changes to your diet.

What should you eat for low blood pressure during pregnancy?

You may need to increase how often you eat and eat smaller meals to help avoid low blood pressure during pregnancy. Reducing carbohydrates while increasing salt intake also may help, but talk to your doctor before making any dietary changes while you are pregnant.

When should you call your doctor about low blood pressure during pregnancy?

Call you doctor immediately if your low blood pressure causes you to feel dizzy or faint or fall.

How do you treat low blood pressure during pregnancy?

Is it OK to have low blood pressure during pregnancy?