OBSTETRICS FOR PAEDIATRICIANS Preterm prelabour rupture of membranes

The problem Unfortunately there are too many examples in obstetrics of very important conditions for which there is no consensus of professional opinion about definition, diagnosis, risks, and above all, management. Preterm prelabour rupture of the membranes (PPROM) is such a case. The best, most widely used, and simplest definition of PPROM is membrane rupture occurring before the onset of regular uterine contractions prior to 37 weeks' gestation. Some authors add caveats, for example, about the interval between membrane rupture and the onset of labour or not including cases above 34 weeks' gestation. In general, these are unhelpful modifications to the definition. However, while not helpful for definition, these two factorsduration of membrane rupture and gestational age-critically influence the risks and management of PPROM. The reported incidence of prelabour membrane rupture in all pregnancies varies from 110% depending on the population studied. However, if elective preterm deliveries and fetal death before labour are excluded, the incidence of PPROM in women delivering preterm is between 40-60%. The main independent risk factors for PPROM are antepartum vaginal bleeding, maternal smoking, and previous preterm delivery. The aetiology and pathogenesis of PPROM are poorly understood. For example, it is not clear whether pregnancies complicated by spontaneous preterm labour and delivery with PPROM should be regarded as different in these respects from cases without preceding membrane rupture. Factors claimed to be possible causes of PPROM include infection, membrane collagen abnormalities, cervical incompetence, raised intrauterine pressure, and low membrane calcium and magnesium content. There have been many theories of the mechanisms whereby these factors produce PPROM with much research currently involving platelet activating factor and prostaglandin metabolism in the membranes. As with most aspects of spontaneous preterm delivery, the explanation remains as elusive as ever. While the causes of PPROM are uncertain the risks are well known. The three serious complications, in order of importance, are preterm labour and delivery and its consequences, infection, and pulmonary hypoplasia. Other important complications are various deformities due to oligohydramnios, placental abruption, cord compression (either due to cord prolapse or severe oligohydramnios), and mechanical difficulties at delivery. There is no information to indicate whether these risks are any different for 'hindwater' as opposed to 'forewater' PPROM thus in practice no distinction is made between the two.