Perinatal management at the lower margin of viability.

Correspondence to: Dr Janet Rennie. Definition Lord Donaldson defined viability as the point when a child can breathe either naturally or with the aid of a ventilator.1 Fetuses of 14 weeks gestation can be born with a heartbeat and may gasp, but cannot sustain life. Live birth is therefore an invalid indicator of viability. Viability is perhaps better defined as the ability both to live and to grow and develop 'normally'.2 Normality is a very imprecise term. Baby K, an anencephalic, remains alive and is growing after several years on a ventilator, although she has not developed any skills at all.3 Most would agree that her existence is not worthwhile and her total lack of development renders her nonviable using the definition of Dunn and Stirrat.2 Even here, however, the hope of a miracle has persuaded the courts to order continuation of life sustaining treatment. Few cases are as clearcut as this and there is often conflict about the quality of life; the parents ofThomas Creedon felt that his lack of development was such that his life was not worth living,4 but it remains to be seen whether a British court would have sanctioned the withdrawal of his gastrostomy feeds. In perinatology difficult quality of life judgments are common. A pure sanctity of life philosophy is not held by many parents, neonatologists, or nurses. Often this judgment involves a pregnancy which threatens to end very early. After 27 weeks gestation intact survival exceeds 50%, whereas intact survival has been reported in only a few children delivered at 22 weeks. I will use the term marginal viability to refer to the period between 23+0 and 26+6 weeks of pregnancy. The live birth of such an infant occurs twice in every thousand deliveries. This neonatal emergency is therefore about as common as the birth of a severely asphyxiated infant at term. The prognosis for the group as a whole is similar to that of severe hypoxic ischaemic encephalopathy, in that 50% of the babies die and 50% of the survivors are handicapped. There is often some warning, however, of very preterm birth and this allows for planning regarding the place and mode of delivery, and time for consultation with the parents. In this review I aim to provide some guidance which the reader can adapt to develop a local protocol. Midwives and junior doctors particularly welcome clear written guidelines in this difficult area, although further senior input is obviously essential at the time.