A cerclage is a surgical procedure involving the placement of strong sutures around the cervix to keep it closed during pregnancy. This intervention physically supports a weakened cervix, a condition often called cervical insufficiency. The primary goal is to maintain the integrity of the lower uterus, preventing premature dilation and subsequent preterm birth. While the stitch protects the pregnancy, patients often worry if the amniotic sac can still rupture—commonly known as a mother’s water breaking—while the cerclage is in place. This complication, called preterm premature rupture of membranes (PPROM), can occur and significantly alters the course of care.
Understanding the Purpose of a Cervical Cerclage
A cervical cerclage is a prophylactic measure employed when a healthcare provider determines there is a high risk of the cervix opening too early. This risk typically arises from a history of second-trimester losses or preterm births. It is also used when an ultrasound reveals the cervix is abnormally short, usually less than 25 millimeters, before the 24th week of gestation. In cases of insufficiency, the cervix can painlessly begin to shorten and open under the pressure of the growing pregnancy.
The surgical placement is typically done through the vagina, often using techniques like the McDonald procedure, which involves a purse-string suture placed high on the cervix. This stitch provides mechanical reinforcement, acting as a physical barrier to hold the cervical tissues together. The procedure is usually performed electively between 12 and 14 weeks of pregnancy, or sometimes as a rescue procedure if cervical changes are observed later. The reinforcement is designed to keep the fetus contained until the pregnancy reaches term, usually around 37 weeks, when the stitch is removed.
The Connection Between Cerclage and Membrane Rupture
Despite the physical support offered by the cerclage, the amniotic sac surrounding the fetus can rupture prematurely. PPROM occurs in a varying percentage of patients with a cerclage, often attributed to the high-risk nature of the underlying condition that required the stitch. The presence of the cerclage itself can sometimes contribute to this risk, though this is debated among clinicians.
The suture material is a foreign body, and its presence can potentially lead to localized inflammation. It can also act as a conduit for ascending infection from the vagina into the uterus. This ascending infection is a significant concern because it weakens the fetal membranes, making them more susceptible to rupture. The stitch itself can also cause direct trauma to the lower membranes, which are held taut by the reinforced cervix.
When the membranes rupture, amniotic fluid drains out, removing the protective cushion for the fetus. This establishes a direct pathway for bacteria to enter the uterus. This complication shifts the focus of care from preventing premature dilation to managing the risks of infection and extreme prematurity. The cerclage increases the risk of chorioamnionitis, a severe infection of the uterine lining and amniotic fluid.
Identifying Signs of Premature Water Breaking
Recognizing the signs of PPROM is paramount for a patient with a cerclage, as immediate medical attention is necessary. The most distinct sign is a sudden gush of warm, clear fluid from the vagina, or a persistent slow trickle. The amount of fluid depends on the size and location of the rupture. A rupture high up may result in only a slow leak, while a tear lower down near the cervix can cause a pronounced gush.
Patients must distinguish this fluid from normal pregnancy discharge or involuntary urination, which is common in late pregnancy. Amniotic fluid is typically clear or straw-colored and is usually odorless or has a faintly sweet smell. Urine, conversely, has a distinct ammonia odor and yellowish color. A helpful way to check for a continuous leak is to sit down for a few minutes and then stand up; if a trickle of fluid follows, it suggests ruptured membranes. Any suspicion of water breaking, especially if the fluid is discolored (green or brown) or has a foul odor, requires immediate contact with a healthcare provider.
Clinical Response Following Membrane Rupture
Once PPROM is confirmed in a patient with a cerclage, the treatment protocol changes immediately to prioritize the health of both the mother and the fetus. The cerclage is typically removed as soon as the diagnosis is made because it increases the risk of infection after the membranes have ruptured. The presence of the stitch provides a surface for bacteria to colonize, significantly raising the risk of chorioamnionitis.
Following cerclage removal, the patient is admitted to the hospital for close monitoring and management. This includes the administration of broad-spectrum antibiotics to prevent maternal infection. Corticosteroids are also given if the gestational age is between 24 and 34 weeks, as these medications accelerate the development of the fetal lungs. The goal of this expectant management is to prolong the time until delivery, known as the latency period, allowing the fetus more time to mature. While retaining the cerclage has been shown in some studies to modestly prolong the latency period, the increased risk of severe maternal infection often makes immediate removal the preferred therapeutic approach.