Labor induction is the process of stimulating the uterus to begin labor before it starts naturally, typically when continuing the pregnancy poses a risk to the mother or the baby. This medical intervention is often necessary when a patient is past their due date, has certain health conditions like preeclampsia, or when the amniotic sac has ruptured without the onset of contractions. The goal of induction is to first achieve cervical ripening, which means softening and thinning the cervix to prepare it for dilation. The Foley bulb is a common, non-pharmacological method used to achieve this preparation.
How the Foley Bulb Works
The Foley bulb is a specialized catheter, a thin, flexible tube made of silicone or rubber with an uninflated balloon tip at one end. A healthcare provider carefully inserts this catheter through the cervix, positioning the balloon just beyond the internal opening of the uterus. Once properly situated, the balloon is inflated with a sterile saline solution, often about 30 to 60 milliliters, which holds the device in place.
The inflated balloon acts as a mechanical dilator, applying gentle and sustained pressure directly against the cervix. This continuous physical tension gradually stretches the cervical tissue, causing it to open. The constant, localized pressure also stimulates the body to release natural prostaglandins, hormones that aid in softening and effacing the cervix. This dual action—mechanical stretching and hormonal release—helps to move the cervix toward a more favorable, thinned, and partially dilated state. The Foley bulb is designed to achieve an initial dilation of approximately three to five centimeters before it falls out naturally.
Medical Reasons for Choosing This Method
A healthcare provider determines the need for induction and the method to use based on a full assessment of the patient’s condition. The Bishop Score is a tool used to gauge the readiness of the cervix for labor, and the Foley bulb is often selected when this score indicates an “unfavorable” or unripe cervix. This mechanical method is frequently preferred over medication-based induction in specific clinical scenarios.
One reason for choosing the Foley bulb is for patients who have previously had a cesarean section. Certain medications used for cervical ripening can increase the risk of uterine hyperstimulation, which carries a risk of a uterine rupture in those with a prior C-section scar. The mechanical action of the bulb carries a lower risk of this over-stimulation compared to hormonal agents. The Foley bulb also provides an option for patients who wish to attempt a drug-free induction, or for those with maternal health conditions like high blood pressure or gestational diabetes where a more cautious approach to induction is warranted.
What to Expect During the Procedure
The process begins with a cervical check to determine the current dilation and effacement. The provider uses a sterile technique, sometimes employing a speculum to visualize the cervix, to insert the tip of the uninflated catheter. The insertion itself is often described as the most uncomfortable part of the procedure, causing a feeling of sharp pressure or intense cramping, though this discomfort is typically temporary.
Once the balloon is threaded past the internal cervical opening, the provider injects the sterile saline solution to inflate it. The catheter is then secured by taping the external end to the patient’s inner thigh, which maintains constant tension on the cervix as dilation begins. This tension ensures the pressure is continually applied, encouraging the cervix to open. After the bulb is placed, the patient and fetus are monitored, though the patient may be able to walk around or rest.
The Foley bulb remains in place until it achieves its maximum dilation, typically three to five centimeters, at which point the balloon slips through the now-open cervix and falls out. This expulsion indicates that the first stage of cervical ripening has been completed. If the bulb does not fall out within a set timeframe, usually around 12 hours, the provider will remove it and assess the next steps for induction. After the cervix has been partially dilated, other induction methods, such as administering the synthetic hormone oxytocin, may be initiated to stimulate contractions and progress labor further.
Potential Risks and Safety Considerations
While the Foley bulb is considered a safe and effective method for cervical ripening, patients should be aware of potential complications. The most commonly reported effect is the pain or discomfort experienced during the insertion and the subsequent cramping as the cervix dilates. There is a risk of infection or fever following the procedure, which necessitates careful monitoring by the healthcare team.
Other rare complications include the accidental rupture of the amniotic membranes during insertion or minor spotting and bleeding from the cervix. In some cases, the bulb may be prematurely displaced or may not be effective in initiating cervical change. The Foley bulb is contraindicated in certain situations, such as when the placenta is positioned over the cervix (placenta previa), or when the patient has an active infection, like genital herpes.