What Causes Vaginal Fluid Leakage in Late Pregnancy?
During the third trimester of pregnancy, vaginal fluid leakage—often described by patients as “water leaking from below”—can signal several possible conditions, ranging from benign to urgent. The most
During the third trimester of pregnancy, vaginal fluid leakage—often described by patients as “water leaking from below”—can signal several possible conditions, ranging from benign to urgent. The most critical concern is preterm or term premature rupture of membranes (PROM), where the amniotic sac ruptures before labor begins. This results in a continuous or intermittent outflow of clear, odorless amniotic fluid, which may be mistaken for urine or normal vaginal discharge. Unlike urine, amniotic fluid typically lacks ammonia-like odor and does not stop with bladder emptying; unlike discharge, it is usually thin, watery, and may increase with coughing or movement.
Other potential causes include increased physiological vaginal discharge due to elevated estrogen levels, urinary incontinence (especially stress incontinence exacerbated by fetal pressure on the bladder), or cervical mucus plug expulsion—a sign that cervical ripening has begun, often accompanied by streaks of blood (“bloody show”). Less commonly, infections such as bacterial vaginosis or candidiasis can alter discharge volume and consistency, though these are typically associated with itching, odor, or irritation.
Any suspected rupture of membranes warrants immediate clinical evaluation. Diagnosis involves sterile speculum examination to assess pooling fluid in the posterior fornix, pH testing (amniotic fluid elevates vaginal pH >4.5, turning nitrazine paper blue), and microscopic examination for ferning patterns on dried fluid. Ultrasound may assess amniotic fluid index to support findings. Prompt assessment is essential: untreated PROM increases risks of intra-amniotic infection, umbilical cord prolapse, and preterm birth complications.
Pregnant individuals experiencing persistent or recurrent fluid leakage—particularly if accompanied by fever, uterine tenderness, foul-smelling discharge, or decreased fetal movement—should seek urgent obstetric care. Timely intervention ensures appropriate management, whether expectant monitoring, antibiotic prophylaxis, induction of labor, or delivery planning based on gestational age and maternal-fetal status.