Preterm Labour

Symptoms

• Regular uterine contractions, often described as feeling like menstrual cramps that come and go. Typically more than 4-6 contractions in an hour.
• Change in vaginal discharge, which may be watery, mucus-like, or bloody (known as 'show').
• A feeling of the baby pushing down, or pelvic pressure.
• Low, dull backache.
• Abdominal cramps, which may or may not be accompanied by diarrhea.
• A general sense that 'something is not right'.
• A gush or continuous trickle of fluid from the vagina, indicating rupture of membranes.
• Significant vaginal bleeding.
• Contractions that are very strong, frequent (e.g., every 5 minutes or less), and painful.
• Decreased fetal movement.

Causes & Risk Factors

• Preterm labour is a complex condition often resulting from multiple factors that trigger early labour. The exact cause is frequently unknown and can be multifactorial.
• Uterine overdistension, which can occur with multiple gestation (twins, triplets) or excessive amniotic fluid (polyhydramnios).
• Decidual hemorrhage or ischemia (reduced blood flow to the uterine lining), potentially due to placental abruption or blood clotting disorders (thrombophilias).
• Premature activation of the maternal or fetal stress response system (hypothalamic-pituitary-adrenal axis), possibly due to maternal or fetal stress.
• Inflammation and infection, such as intra-amniotic infection (chorioamnionitis), urinary tract infections (UTIs), or periodontal (gum) disease.
• In approximately 50% of spontaneous preterm births, a specific cause is not identified; this is referred to as idiopathic preterm labour.
• Previous preterm birth (this is the strongest single predictor).
• Multiple gestation (e.g., twins, triplets).
• Uterine or cervical abnormalities, such as a bicornuate uterus, uterine fibroids, or a history of cervical surgery (e.g., LEEP/LLETZ).
• Maternal age: being younger than 18 years or older than 35 years.
• Ethnicity: Black race is associated with a higher risk in some populations (e.g., USA).
• Short interpregnancy interval: less than 18 months between birth and subsequent conception.
• Genetic predisposition.
• Short cervical length, as measured by transvaginal ultrasound in the second trimester.
• Infections, including urinary tract infections (UTIs), bacterial vaginosis, periodontal disease, or systemic infections.
• Preterm prelabour rupture of membranes (P-PROM), where the water breaks before labour begins and before 37 weeks.
• Vaginal bleeding during pregnancy.
• Placental issues, such as placenta previa (placenta covering the cervix) or placental abruption (placenta separating from the uterus early).
• Maternal health conditions like high blood pressure (hypertension), pre-eclampsia, or diabetes.
• Lifestyle factors including smoking, substance abuse (e.g., cocaine), low socioeconomic status, high levels of stress, poor nutrition, or low pre-pregnancy weight.
• Assisted Reproductive Technology (ART).
• Heavy physical work or prolonged standing (possible risk factor).
• High levels of psychological stress or depression (possible risk factor).
• Specific micronutrient deficiencies (currently under investigation as a possible risk factor).
• Normal pre-pregnancy body mass index (BMI).
• Adequate interpregnancy interval (time between pregnancies).
• Absence of known risk factors.
• Prophylactic treatments in high-risk individuals, such as progesterone supplementation or cervical cerclage.

Diagnosis

• Diagnosis is based on a clinical assessment, considering:
• Gestational age: between 20 weeks 0 days and 36 weeks 6 days.
• Regular uterine contractions: for example, 4 or more contractions in 20 minutes, or 8 or more in 60 minutes.
• AND Cervical change: cervical dilatation of 3 cm or more (ACOG guideline) or more than 2 cm (NICE guideline), or a documented change in cervical effacement (thinning) or dilatation over time.
• A review of your symptoms, including contractions, bleeding, or discharge.
• An assessment of any risk factors you may have, such as a prior preterm birth.
• A review of your current pregnancy course.
• A sterile speculum examination to check for ruptured membranes (looking for fluid pooling, performing a ferning test, or nitrazine test) and to visualize the cervix.
• A digital cervical examination to assess cervical dilatation, effacement, consistency, and position. This may be deferred if preterm prelabour rupture of membranes (P-PROM) is suspected until after the speculum exam.
• Assessment of uterine activity, including the frequency, duration, and strength of contractions.
• Monitoring of maternal vital signs and fetal heart rate.
• Fetal Fibronectin (fFN) test: This test detects a glycoprotein in cervicovaginal secretions. A negative result is highly reassuring that delivery is unlikely within the next 7-14 days. A positive result indicates an increased risk but is less precise in confirming imminent delivery. It is typically used in symptomatic women with intact membranes between 22 and 34 weeks gestation and a cervical length of 20-30 mm or when the diagnosis is uncertain.
• Urine culture: To check for and rule out a urinary tract infection (UTI).
• Vaginal/rectal swab: For Group B Streptococcus (GBS) screening.
• Transvaginal Ultrasound (TVUS): Used to measure cervical length. A short cervix (less than 25 mm) is a strong predictor of preterm birth risk. This can be used for screening in asymptomatic high-risk women and for diagnosis in symptomatic women.
• Braxton Hicks contractions (irregular, non-painful contractions without cervical change).
• Urinary tract infection (UTI).
• Placental abruption.
• Appendicitis.
• Dehydration.

Treatment Options

• Antenatal Corticosteroids: Recommended for women between 24 weeks 0 days and 33 weeks 6 days of gestation who are at risk of preterm delivery within 7 days. They may also be considered at 23 weeks 0 days. For women between 34 weeks 0 days and 36 weeks 6 days at risk of delivery within 7 days who have not previously received them, ACOG also recommends their use. Medications like Betamethasone or Dexamethasone are used to accelerate fetal lung maturity and reduce the risk of neonatal respiratory distress syndrome, bleeding in the brain (intraventricular hemorrhage), and a severe intestinal disease (necrotizing enterocolitis).
• Tocolytics (drugs to stop contractions): These medications are used to delay delivery for up to 48 hours. This delay allows time for antenatal corticosteroids to take full effect and for transfer to a facility with a neonatal intensive care unit (NICU) if needed. Guidelines for specific medications can vary: ACOG recommends beta-adrenergic receptor agonists (e.g., terbutaline), calcium channel blockers (e.g., nifedipine), and NSAIDs (e.g., indomethacin) as first-line options. NICE/RCOG recommend nifedipine as the first-line tocolytic, with atosiban (an oxytocin receptor antagonist) as another option. Tocolysis is generally not recommended after 34 weeks of gestation or if delivery is medically indicated (e.g., severe pre-eclampsia, infection of the amniotic fluid, or fetal distress).
• Magnesium Sulfate: Administered for fetal neuroprotection when delivery is anticipated before 32 weeks of gestation. Its purpose is to reduce the risk and severity of cerebral palsy in surviving infants.
• Antibiotics: Indicated for Group B Streptococcus (GBS) prophylaxis if your GBS status is positive or unknown. Antibiotics are not recommended solely to prolong gestation or treat preterm labour in women with intact membranes, as this may be harmful.
• Rescue Cerclage: A stitch placed in the cervix. This may be considered in specific cases where the cervix is dilated but the membranes are not ruptured. Evidence for its efficacy in this context is limited.
• Watchful Waiting: This approach may be appropriate for women who have symptoms of preterm labour but no documented cervical change, especially if the fetal fibronectin (fFN) test is negative and cervical length is normal.
• Any woman diagnosed with preterm labour should be managed in a hospital with an appropriate level of neonatal care (NICU).
• Transfer to a tertiary care center (a hospital with higher-level specialized care) may be required for pregnancies less than 32 weeks of gestation.

Frequently Asked Questions