Vagal Response in Pregnancy: What Is It and How to Prevent It?

We'll tell you all about this condition that anyone can suffer but which pregnant women are more likely to suffer from.

Reviewed and approved by the nurse Leidy Mora Molina.

Written by Edith Sánchez

Last update: 15 December, 2023

Vagal response symptoms occur mainly in mid-pregnancy. Although they are considered a pathology, they don’t require treatment and, in most cases, have no major consequences.

Anyone can experience vagal response symptoms at some point in their lives. It’s estimated that up to 20% of people have had them at some time. However, it’s more common in pregnant women due to the physiological changes that occur during pregnancy.

In vagal response, there are various symptoms such as flushing, paleness, a feeling of weakness, sweating, and blurred vision. Sometimes these symptoms can even lead to loss of consciousness. The danger is in the fall or when driving or in similar situations.

What is the vagal response in pregnancy?

Vagal response is also known as “vagal syncope”, “vasovagal response” or “neurocardiogenic syncope”. It consists of a series of initial symptoms, or prodromes, often culminating in fainting.

They occur as a result of excessive stimulation of the vagus nerve. This leads to the dilation of the blood vessels and a reduction in heart rate and blood pressure. Under these conditions, less blood reaches the brain and syncope, or fainting, occurs.

Vagal symptoms may be said to be caused by a sudden drop in blood pressure. Not all pregnant women have vagal symptoms, but this problem is nonetheless very common. In some pregnant women, it becomes very frequent and severe.

Why do they occur?

Science hasn’t been able to establish a specific cause of vagal symptoms. However, it’s believed to be more common in people with a high peripheral  venous load. That is, in people who have some condition that hinders or slows the return of blood to the heart and brain.

Under usual conditions, vagal pictures occur for reasons such as the following:

• Sudden changes in position
• Changes in altitude
• Standing or sitting for long periods of time
• When straining to urinate, defecate or cough
• Stress or anxiety
• Dehydration
• Hunger
• Nausea or vomiting
• Allergies to certain medications
• Alcohol or drug use

However, vagal symptoms are more frequent in pregnant women for two reasons:

• Hormonal changes.
• Venous stasis in the lower extremities. There is difficulty in the blood returning in the legs.

There’s also an anatomical reason why it’s easier for vagal syncope to occur during pregnancy. When the pregnant woman sits for a long time, the weight of the belly overstimulates the vagal nerve. As we have already explained, this precipitates the condition.

Symptoms

Typically, in vagal conditions, certain symptoms occur before the loss of consciousness or fainting occurs. It’s very important to know about these initial symptoms, as this allows early action to prevent fainting.

The usual symptoms are as follows:

• A sensation of heat
• Cold, clammy sweating
• Nausea
• Lightheadedness
• Narrowing of the visual field (tunnel vision) or blurred vision
• Ringing in the ears
• Tachycardia
• Pallor
• Feeling of weakness
• Fatigue

Fainting usually occurs after experiencing these symptoms. The loss of consciousness is of short duration and spontaneous recovery, almost always in less than a minute.

How to prevent them

Some basic measures can help to prevent vagal symptoms. They’re especially useful for pregnant women who are very prone to suffer from them. These are simple habits that are well worth incorporating into your daily routine.

What you should do is the following:

• Don’t remain seated for long periods. After a couple of hours, get up and walk around a bit.
• Don’t stand for long periods. When you feel tired, the best thing to do is to sit down for a moment or take a few steps.
• Avoid sudden changes of position. When standing up, sitting down, or getting out of bed, it’s advisable to do it slowly, avoiding sudden changes of position.
• Keep spaces well-ventilated. This is even more important in hot weather.
• Eat something every three hours. A small portion of some healthy food avoids incurring in very long fasts.
• Avoid stuffy environments.
• Breathe deeply for a couple of minutes if you experience stress.

What to do when there are symptoms

It’s very important to know what to do when the first symptoms of vagal symptoms occur. The goal is to avoid syncope or fainting since a fall could be very dangerous for a pregnant woman.

The recommended measures are the following:

• Lying down. This should be done gently, avoiding rapid movements. It’s best to raise your legs for a few minutes. This helps the blood to rise again, thus normalizing the functioning of the heart and brain.
• Breathe deeply. It’s best to breathe in and out slowly, without any hurry. Otherwise, hyperventilation may occur.
• Keep calm. It’s important to remain calm. If the pregnant woman is alone, it’s advisable to ask for help while she gets over the episode.

Consult your doctor if you have had vagal syncope

When regaining consciousness after fainting caused by vagal response symptoms, it’s best to lie down and not stand up until 15 to 30 minutes after the episode. Pregnant women who frequently suffer from these symptoms should refrain from driving, as it can be very dangerous.

Although there’s no specific treatment for vagal symptoms, it’s best to tell your doctor immediately after the first episode. This will allow a more detailed follow-up of the case.