When and How Supine Hypotension Syndrome occurs

Supine hypotension syndrome also called “inferior vena cava compression syndrome” is occurs when the uterus compresses the inferior vena cava when a pregnant woman is in the supine position, i.e., lying on the back, and this leads to reduced venous return centrally.

“Supine” means lying on the back, and “hypotension” is low blood pressure. During pregnancy, when you lie on your back, the weight of the baby and your uterus compresses down your spine and abdominal organs. This pressure from the baby and uterus can squeeze the two largest blood vessels of the body, namely the aorta and inferior vena cava. The compressions of the two blood vessels can affect the blood circulation or the flow in the body. The blood flow reverting to the heart may slow down, decreasing the amount of blood the heart pumps out. When the blood pressure falls, this will interrupt the blood flow from the uterus to the baby.

Up to 8% of women who are in their second and third trimesters of pregnancy can be affected by this syndrome. The symptoms of supine hypotension syndrome typically occur within 10 minutes after lying down. Further, into the pregnancy, the uterus grows in size with increasing gestational period, and the compression becomes a more usual thing.

Supine hypotension is typically diagnosed by a reduction in systolic BP of at least 15 mm to 30mm Hg. In severe cases, pregnant women may even lose consciousness. Therefore, it is advised to avoid lying on the back for an extended period after 24 weeks of pregnancy. If you see symptoms of this syndrome, then you must move into left lateral positions for the symptoms to recede.

What is blood pressure?

Our heartbeats and pumps blood to every part of the body. Every pump sends blood with force. Therefore, the force at which the blood pumps through the arteries is known as blood pressure. We measure blood pressure in systolic over diastolic pressure.

Blood pressure = The systolic pressure / the diastolic pressure

Normal blood pressure is less than 120 millimeters of mercury (mm Hg) over 80 mm Hg.

The hormones dilate or expand the blood vessels in pregnancy and open up additional vessels for extra circulation. This is why blood pressure typically goes down. The blood pressure goes both ways, i.e., up or down. While resting, the blood pressure goes down and goes up when excited, stresses, and working.

Supine hypotension syndrome is not the regular rise and fall of blood pressure in pregnancy. This reduces the systolic pressure by at least 15mm to 30mm Hg when lying on the back. Although the condition is dependent on the shape, size, and weight of the uterus, this condition is more prone for women carrying multiples and those with” body mass index” in the obese range. If the body mass index or BMI is less than 18.5, it falls under the underweight range. The healthy weight range is between 18.5-25. Any more than 25.0 but under 30 it falls under overweight and above 30 falls under obesity range.

Supine Hypotension Syndrome

Symptoms of SHS

The symptoms of this syndrome involve –

  • Lower heart rate (bradycardia)
  • Sweating
  • Dizziness
  • Turning pale
  • Weakness
  • Shortness of breath
  • Fainting
  • Nausea

You may experience the above-stated symptoms within three to ten minutes of lying down.

 Who are at risk of this syndrome?

As you progress into further weeks of pregnancy, the uterus and the fetus grow and weigh more, leading to blood vessels compression. Not all women experience this condition, but some are at risk given that they –

  • Are carrying multiples
  • Have a large and heavy uterus with a lot of amniotic fluid
  • The baby or babies are in a position that compresses the blood vessels
  • Are over 20 weeks along
  • Have a heart condition
  • The collateral circulation system is not working efficiently
  • BMI is above 25.0

How to treat Supine Hypotension Syndrome

If you feel symptoms of low blood pressure when lying on the back, you need to –

  • Turn onto your left side
  • Change sides
  • Avoid lying on the back
  • If symptoms persist, consult a doctor at the earliest

In case you are in hospital, having a test/in labour/in an emergency, then the healthcare specialist or the healthcare team may treat you by

  • Provide you with oxygen
  • Delivering the baby
  • Elevating the head
  • Moving the uterus over to the side

Medically or surgically treating the underlying cause What are some situations when you might experience this syndrome?

In pregnancy, supine hypotension syndrome may happen at any time while you lie down on your back. Here are some possible situations during which you might experience this syndrome

  • Sleeping with your back flat from mid-pregnancy
  • Lying on the back during labor
  • Lying on the back during C-section
  • After twenty of pregnancy, exercising while lying flat on the back
  • While vising a dentist
  •  Getting an MRI
  • Taking any tests which require you to lie on your back
  • In case of trauma such as a vehicular accident when you need to go on an emergency backboard

Complications caused due to supine hypotension syndrome?

The pressure on the aorta and inferior vena cava can lead to an interruption in the flow of your blood. When blood does not normally return from the lower back to the heart, it may get blocked in the veins of the lower back. If the flow of blood is blocked or is lowered for too long, it may lead to complications like –

  • Hemorrhoids
  • Blood clots in the lower extremities (deep vein thrombosis)
  • Swelling (edema) in the lower body
  • Swollen varicose veins in your legs
  • Varicose veins in your vulva
  • In exceptional cases, it can even lead to
  • Shock
  • Loss of consciousness
  • Death of mother
  • Stillbirth
  • Reduced supply of oxygen to the placenta
  • The slow growth of the baby

Tips to avoid supine hypotension syndrome

  • First and foremost, avoid lying on your back. Try sleeping on the sides; you can make this more comfortable by placing pillows for support. You may also try sleeping in an inclined position where the upper body is slightly above the lower body. Don’t panic if you wake up in a position different from the one you to bed in. It is normal to change sides in sleep; you will wake up if something is incorrect.  
  • Avoid any exercise that requires you to lie on your back in and after the second trimester. The exercises include yoga, Pilates, or any other activities that need lying down flat on the back.
  • If you are lying flat on the back and feel any symptoms of the syndrome, slowly change your position towards lift or sit up.
  • Use proper pillows and a mattress topper to ease the pressure on the hips due to side sleeping.
  • Be careful while standing up from a lying position, especially if you are feeling dizzy. Rise slowly with the help of proper support.
  • You don’t require to lie flat during labor unless you have any complications. Consult your healthcare specialist regarding this.
  • If you visit a dentist, a masseuse, or any other place, let people know about your condition and needs and make sure you don’t lie flat on the back. Pregnancy is not always obvious.

Again ups and downs blood pressure is normal during pregnancy, whereas supine syndrome is altogether a different story. Don’t panic due to a slight drop in blood pressure, as this is not a threat to you or your baby.

Your doctor usually checks your blood pressure in every visit. However, consult a doctor without further ado if you see any symptoms or think something is not correct. 

Supine hypotension syndrome is dangerous, so if you get any of the symptoms mentioned above. Get checked and be sure that it is not the case. As we know now that this can disrupt the blood circulation to the baby, so this is not something we can risk with. Therefore, be clear of your situation and make all efforts to keep your baby and you safe.

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