Betamethasone is a corticosteroid medication administered via intramuscular (IM) injection to pregnant patients at risk of preterm delivery, typically between 24 and 34 weeks of gestation. The primary purpose of this treatment is to accelerate the maturation of fetal lungs by stimulating the production and release of surfactant, a substance that prevents the air sacs from collapsing. IM delivery ensures systemic absorption, allowing the drug to cross the placenta and reach the developing fetus. A full course of therapy, often consisting of two 12-milligram doses administered 24 hours apart, significantly reduces the incidence of respiratory distress syndrome, intracranial hemorrhage, and necrotizing enterocolitis in premature infants.
Anatomical Selection for Intramuscular Administration
The selection of a proper injection site is important to ensure the medication is delivered into the muscle layer while avoiding major nerves and blood vessels. The preferred site for betamethasone administration is the ventrogluteal area due to its considerable muscle mass and safety profile. This site utilizes the gluteus medius and minimus muscles and is less likely to contain large nerves or blood vessels compared to other common injection locations.
To locate the ventrogluteal site, a healthcare provider places the heel of their hand over the patient’s greater trochanter, which is the bony prominence on the side of the hip. The index finger is then placed on the anterior superior iliac spine, and the middle finger is extended toward the iliac crest, forming a distinctive V-shape. The injection is administered into the center of this V-shaped triangle, ensuring a deep injection into the muscle tissue.
The vastus lateralis muscle, located on the anterolateral aspect of the thigh, is an acceptable alternative. This large muscle is easily accessible and a suitable option if the ventrogluteal site is unavailable or the patient cannot be positioned comfortably. The safe injection zone is identified by dividing the area between one hand-width below the groin and one hand-width above the knee into thirds. The injection is given into the outer middle third of this area.
Modern clinical practice generally avoids the dorsogluteal site (the traditional upper outer quadrant of the buttock) due to the increased risk of injecting near the sciatic nerve. Selecting the safer ventrogluteal or vastus lateralis site minimizes the chance of nerve damage, pain, and localized injury.
Detailed Injection Technique and Preparation
The physical technique used for the intramuscular administration of betamethasone is crucial for preventing complications. Aseptic preparation is required, beginning with cleaning the skin at the chosen site with an antiseptic solution and allowing it to dry completely. Proper needle selection is based on the patient’s weight and muscle mass to guarantee the medication reaches the deep muscle tissue.
For most adult patients, a needle gauge between 22 and 25 is appropriate, with a length typically ranging from 1 to 1.5 inches. A longer needle, such as 1.5 inches, may be necessary for patients with a higher body mass index to penetrate the subcutaneous fat layer and reach the muscle. The patient should be positioned to ensure the target muscle is relaxed, which is often achieved by having the patient lie on their side with the upper leg slightly flexed for a ventrogluteal injection.
The Z-track method is the preferred technique for this injection, used to seal the medication within the muscle layer. This involves using the non-dominant hand to laterally pull the skin and subcutaneous tissue approximately one to one-and-a-half inches away from the injection site. The needle is then inserted quickly at a 90-degree angle to the skin surface.
While maintaining skin displacement, the medication is injected slowly to minimize discomfort and allow the muscle fibers to accommodate the fluid volume. A common recommendation is to inject at a rate of about 10 seconds per milliliter. After the full dose is delivered, the needle is kept in place for about 10 seconds before being withdrawn smoothly. Releasing the displaced skin immediately after removal creates a zigzag path that closes the needle track, preventing the concentrated corticosteroid from tracking back into the sensitive subcutaneous tissue and causing irritation or localized skin damage.
Clinical Monitoring and Safety Considerations
Following the injection of betamethasone, the patient requires a period of clinical observation to monitor for expected side effects and any rare adverse reactions. A common maternal effect is a transient increase in blood glucose levels, which results from the systemic action of the corticosteroid. This temporary hyperglycemia is particularly important to monitor in patients with pre-existing diabetes or gestational diabetes, potentially requiring a short-term adjustment to their insulin or dietary management plan.
Other temporary maternal side effects can include facial flushing, mild fluid retention, or a feeling of restlessness. Fetal monitoring is also a standard part of post-injection care, as the steroid can cause temporary changes in the fetus. Specifically, a transient suppression of fetal breathing movements and a temporary decrease in fetal heart rate variability may be observed within the first 48 hours after administration.
These fetal changes are typically short-lived and resolve without intervention, but they require close surveillance through non-stress tests or biophysical profiles to ensure fetal well-being. Betamethasone should not be administered if the patient has an active systemic infection or certain other medical conditions, as the steroid could compromise the body’s immune response. The healthcare team must evaluate the benefits of accelerated fetal lung maturity against any immediate risks to the mother.