Background The incidence of congenital heart defects (CHD) is around 1% in general population. A critical CHD is defined as any CHD needing surgery or intervention within first month or leading to death. CHD is considered serious when it needs surgery or intervention within first month or leading to death. The incidence of CHDs in preterm infants remains unknown.

Aims 1. To establish the spectrum of CHD diagnoses and their outcomes in preterm infants <36 weeks of gestation

2. To assess the use of prostaglandin E1 (Prostin) in CHD including initiation and duration of treatment while waiting for surgery or intervention

Methods A retrospective observational study of all the preterm infants with a diagnosis of CHD and admitted to NICU in Cambridge between May 2008 and May 2016. The data was collected from the electronic patient records. Minor CHDs like PDA and PFO were excluded.

Results A total of 95 preterm infants with a diagnosis of CHD were identified. 19% were classified as critical CHDs while 38% had an underlying serious CHD. 43% had significant CHD needing monitoring for one year of age. 1% infants were born <32 weeks of gestation while 23% (22 of 95) were born extremely premature (<28 weeks of gestation). The median gestation age was 32+5 weeks (range: 23+3–36+6 weeks). The median birth weight was 1710g (range: 445–3140g). f those with a critical diagnosis, 33% had intra-uterine growth restriction (IUGR) while 42% of infants with a serious diagnosis had IUGR. Around half of the infants with critical CHD had aortic arch abnormalities. 17% cases (16 of the 95) in our cohort had duct-dependent CHDs. The median duration of prostin infusion was 3.5 days (range: 1–61 days). Overall survival rate was 88% in our cohort.

Conclusions In our cohort, the outcomes in the preterm infants diagnosed with CHD are reassuring, even in the critical and serious CHDs needing long term prostin infusion. Interestingly, the rate of IUGR was much higher in infants with a critical or serious condition. We would recommend a prospective study on the neurodevelopmental outcomes in these infants.