Spontaneous preterm birth is a birth that occurs on its own before 37 completed weeks of gestation, beginning with the spontaneous onset of labor. It is distinct from a medically indicated preterm birth, where providers deliver the baby early due to health risks for the mother or baby, such as severe preeclampsia. These births are categorized into two main types: those following labor with intact fetal membranes, and those that follow preterm premature rupture of the membranes (PPROM), where the amniotic sac breaks before labor starts.
Underlying Risk Factors
Several factors can increase the likelihood of a spontaneous preterm birth, with a previous spontaneous preterm birth being one of the strongest predictors. Another risk factor is carrying more than one baby, such as twins or triplets, as the overdistension of the uterus can lead to earlier labor.
Certain medical conditions and infections also play a part. Abnormalities in the structure of the uterus or a shortened cervix can make it difficult to carry a pregnancy to term. Infections, including those of the urinary tract or gums, can trigger an inflammatory response that stimulates uterine contractions and initiates labor prematurely.
Demographic and lifestyle factors also contribute. Maternal age is a consideration, with women who are very young (under 18) or over 35 being at higher risk. Smoking during pregnancy and a short interval between pregnancies (less than six months) have been identified as risk factors.
Warning Signs and Diagnostic Methods
Recognizing the warning signs of preterm labor is an important step in seeking timely medical care. Symptoms can include:
- Regular or frequent uterine contractions, which may feel like a tightening or hardening of the abdomen
- A persistent, dull lower backache
- A feeling of pressure in the pelvic or lower abdominal area
- Mild abdominal cramps
- A change in the type or amount of vaginal discharge, such as a sudden increase in watery fluid or the appearance of pinkish or brownish mucus
When preterm labor is suspected, clinicians use specific diagnostic tools. A transvaginal ultrasound is a common method used to measure the length of the cervix. A shorter-than-normal cervix can indicate an increased risk for imminent delivery, helping doctors determine the likelihood of birth occurring within a short timeframe.
Another diagnostic tool is the fetal fibronectin (fFN) test. Fetal fibronectin is a protein that acts as a “glue” holding the fetal sac to the uterine lining. A sample of cervicovaginal fluid is collected to check for the presence of this protein. If fFN is detected between 22 and 34 weeks of pregnancy, it suggests a disruption at the maternal-fetal interface and an elevated risk of preterm birth.
Medical Management Strategies
For individuals at high risk for spontaneous preterm birth, preventative strategies may be employed. One strategy is progesterone supplementation, a hormone that helps maintain pregnancy. Administering it can reduce the risk of early delivery in women with a history of spontaneous preterm birth or a short cervix. Another preventative measure is a cervical cerclage, a procedure where a stitch is placed in the cervix to help keep it closed.
When a person is in active preterm labor, the focus of medical management shifts to improving outcomes for the baby. A course of corticosteroids is often administered to the mother. These medications accelerate the development of the baby’s lungs, reducing the severity of respiratory distress syndrome if the baby is born early. The benefits are maximized when delivery can be delayed for at least 48 hours after the first dose.
To provide this window for the corticosteroids to work, medications called tocolytics may be used to temporarily slow or stop uterine contractions. While they do not typically prevent preterm birth altogether, they can delay delivery for a few days. For births anticipated before 32 weeks of gestation, magnesium sulfate is often administered. This medication provides neuroprotection for the baby, lowering the risk of developing cerebral palsy.
Health Outcomes for Preterm Infants
The health challenges a preterm infant faces are directly related to gestational age at birth, as earlier births carry a higher risk of complications. Many of these issues stem from the immaturity of their organ systems. The respiratory system is a primary concern, as underdeveloped lungs can lead to respiratory distress syndrome, requiring breathing support. These infants are also more vulnerable to apneic episodes, where they temporarily stop breathing.
The brain of a preterm infant is also susceptible to injury. The blood vessels in the brain are fragile and can be prone to bleeding, a condition known as intraventricular hemorrhage. This can lead to long-term neurological issues, including developmental delays and cerebral palsy. Feeding and digestion also present hurdles, as the coordination required for sucking, swallowing, and breathing may not be fully developed.
To manage these complex health needs, preterm infants are cared for in a Neonatal Intensive Care Unit (NICU). The NICU provides a specialized environment with advanced technology and a team of experts to support the unique needs of these babies. Care includes temperature regulation in incubators, nutritional support through intravenous lines or specialized feeding methods, and continuous monitoring of vital functions. This intensive care supports organ development and manages complications, improving survival rates and long-term health.