Objective: To identify the population prevalence, pregnancy outcome, and the pattern of associated anomalies with a prenatal diagnosis of cystic hygroma.
Design: We analysed the pregnancy outcomes from 99 cases of prenatally diagnosed cystic hygroma reported to the Trent Congenital Anomalies Register from 1 January 1997 to 31 December 1999, by means of an outcome reporting form completed by the notifying centre.
Results: We identified a population prevalence of 1 in 1775 livebirths for prenatally diagnosed cystic hygroma. There were 64 terminations of pregnancy, 19 spontaneous pregnancy failures, and 16 livebirths. Of the 87 pregnancies karyotyped, 53 (61%) demonstrated aneuploidy with Turner syndrome being the most common, 29 (33%). There were a large variety of structural malformations identified, however, only 14 out of 83 terminations of pregnancy and spontaneous pregnancy failures had post-mortem examinations. Termination of pregnancy for Turner syndrome not complicated by identified structural malformations was the norm. Of the 16 livebirths, only 6 were normal at birth, 1 other has had successful hygroma surgery. Four of the liveborn infants have since died.
Conclusions: The 'normal outcome' rate from pregnancies complicated by prenatally diagnosed cystic hygroma is less than 10% in this study (6/99). Prenatal diagnosis of cystic hygroma requires careful assessment of the fetus, with regard to both karyotyping and ultrasound. Post-mortem examination should be encouraged after termination of pregnancy, or spontaneous pregnancy loss. This is important not just to the current pregnancy but also for future pregnancies.