Clinical situation
A primigravida at term develops dizziness, pallor, diaphoresis, and hypotension while lying supine. The uterus compresses the inferior vena cava, reducing venous return and cardiac output. The first action is to relieve that compression by turning her onto her left side.
Why left lateral positioning comes first
In late pregnancy, the gravid uterus can compress the inferior vena cava when the woman lies flat on her back. This reduces venous return to the right heart, lowers cardiac output, and decreases placental perfusion. The resulting clinical picture is supine hypotensive syndrome, also called aortocaval compression syndrome. Turning the woman to the left side shifts the uterus off the vena cava, restoring venous return and blood pressure within minutes [1][2].
Pathophysiology in simple terms
The inferior vena cava lies slightly to the right of the spine. In the supine position, the heavy term uterus can press directly on this thin-walled vessel. Reduced venous return leads to decreased preload, decreased stroke volume, and a fall in cardiac output, which manifests as hypotension and reflex symptoms such as dizziness, pallor, and sweating. The aorta may also be compressed, further reducing uteroplacental blood flow [2][4].
Why the other options are not first| Intervention | Why it is not the first action |
|---|
| Increase IV fluid rate | Fluid boluses can support preload, but they do not remove the mechanical obstruction. The uterus is still compressing the vena cava, so the underlying cause remains. |
| Trendelenburg position | This position does not reliably relieve vena caval compression and may worsen respiratory mechanics. Left lateral tilt or full left lateral positioning is the standard maneuver [1]. |
| Oxygen 10 L/min by mask | Oxygen may be helpful if hypoxia or fetal distress is present, but it does not correct the primary problem of reduced venous return from caval compression. |
Clinical recognition and monitoring
Symptoms can range from vague complaints to severe hypotension, loss of consciousness, and fetal depression [2]. A drop in systolic blood pressure of 15–30 mmHg or a heart rate increase of 20 bpm with or without symptoms may indicate supine hypotensive syndrome [4]. In this case, the blood pressure fell from 112/70 mmHg to 88/54 mmHg, a systolic drop of 24 mmHg, which fits the definition.
Key point! The first nursing action is always to remove the cause: reposition the woman off her back. A left lateral position or at least a 15° left lateral tilt is the standard immediate intervention for suspected supine hypotensive syndrome. [1][2]
Watch out! Do not delay repositioning to start IV fluids or oxygen. Those are adjuncts to consider only if hypotension persists after the uterus is shifted off the vena cava.
Application to the labor and delivery unit
During abdominal examinations, fetal monitoring, or any procedure requiring supine positioning in late pregnancy, the nurse should anticipate the risk of aortocaval compression. Routine use of a left lateral tilt or a wedge under the right hip can prevent supine hypotensive syndrome before symptoms develop. If symptoms appear, immediate left lateral positioning remains the priority because it directly addresses the mechanical obstruction [1][2].
References (research sources)
- [1]
Supine hypotensive syndrome of pregnancy: A review of current knowledge.Research articleMassoth C, Chappell D, Kranke P, Wenk M (2022) · DOI: 10.1097/EJA.0000000000001554
- [2]
[Aortocaval compression syndrome].Research articleKiefer RT, Ploppa A, Dieterich HJ (2003) · DOI: 10.1007/s00101-003-0596-6
- [4]
Hemodynamic changes in women with symptoms of supine hypotensive syndrome.Research articleHumphries A, Mirjalili SA, Tarr GP, Thompson JMD, Stone P (2020) · DOI: 10.1111/aogs.13789