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“Doc, My Water Bag Burst!” Prelabour Rupture of Membranes (PROM)

C was bathing when she suddenly felt a gush of clear watery fluid flowing out of her vagina. Taken aback, she quickly finished her bath and alerted her husband who rushed her to the hospital.

C, a 28-year-old financial executive was a first-time mum at her 33 weeks of gestation. She was seen early in the first trimester and her antenatal checkups had been normal. She was a non-smoker and there was no history of vaginal bleeding. She did not engage in vigorous exercise or sexual activity recently.

C looked anxious on examination. Her body temperature, blood pressure and pulse rate were normal. Ultrasound scan of the abdomen revealed that her foetus appeared normal and weighed about 1.7 kg. The fetal heart was beating at 156 beats per minute. The amount of amniotic fluid surrounding the foetus was normal. There were occasional painless Braxton-Hicks uterine contractions.

Speculum examination of the vagina found a pool of clear fluid in the posterior recess of the vagina. This was confirmed to be the amniotic fluid by the swab test (Amnicator) which showed a pH value of 7.1. C had ruptured her water bag before the onset of labour, a condition known as prelabour rupture of membranes or PROM. As this occurred before 37 weeks of gestation, it is called “preterm PROM”.

How often is Preterm PROM?

Preterm PROM occurs in about three in a hundred pregnancies and is associated with 30 to 40 % of preterm births

What are the causes and risk factors of preterm PROM?

The cause in most cases is not known. Risk factors include:

  • Having a short cervix (neck of the womb).

  • Infection of the reproductive organs.

  • History of preterm birth in a previous pregnancy.

  • Vaginal bleeding during pregnancy especially in the second and third trimesters.

  • Smoking or taking illicit drugs during pregnancy.

  • Low socioeconomic status.