Background Neonatal thrombocytopenia (NT) is defined as platelet counts less than 150,000/microL, is most common haematological abnormality in the neonatal periods particularly in preterm infants and VLBW.

Objectives We evaluated the maternal-neonatal risk factors, causes, day of onset, duration of NT and the indications of platelet transfusions by means of a retrospective cohort study over a 3-years period.

Methods We conducted a retrospective analysis of prospectively collected data of all neonates born at Singapore General Hospital from year 2017 to 2019. Maternal characteristics like (age, number of pregnancies, medical conditions including maternal thrombocytopenia, pre-eclampsia, pregnancy induced hypertension, maternal age, intrauterine growth retardation, placental Doppler, mode of delivery and multiple births. Neonatal data included gestational age, birth weight, gender, mode of delivery, Apgar scores at 1 and 5 minutes of life, early or late onset sepsis, necrotizing enterocolitis (NEC), intraventricular haemorrhage (IVH), TORCH infections, asphyxia, bleeding site, were collected. The likely cause of NT, Day of life (DOL) of onset of NT, resolution >150 000, Nadir of platelet count (mean) and severity of NT were collected. Early onset NT is onset <72 hours and late onset NT as onset >72 hours.

Results Total of 5196 live-born neonates were studied, 73(0.014%) were found to have NT. The incidence was higher among Very Low Birth Weight (VLBW, <1500 g) (29.1%) and preterm <32 weeks (27.7%). Significant maternal factors for NT included higher maternal age (33.3 years vs 31.6, p=0.02) and pre-eclampsia (9.1% vs 3.9%, p=0.02). Significant neonatal factors included being prematurity <32 weeks (58.9% vs 2.6%, p=0.000), birthweight <1500 g (57.5% vs 19.9%, p=0.000) and lower mean Apgar scores at birth(p=0.000). Total of 41/73(56.1%) infants required platelet transfusions. NT that were transfused versus not transfused, other than maternal pre-eclampsia (24.4% vs 12.5%, p=0.242), the rest of the factors listed above were found to be statistically significant.

For the first onset of NT, majority of transfused infants had early onset thrombocytopenia (53.6% versus 62.5% in the non-transfused population, p=0.448). The mean day of onset of NT was 3.9 days in the transfused population and 2.9 days in the non-transfused population.

Majority had mild thrombocytopenia, not transfused, resolved in the first week of life. the predominant causes were mostly maternal factors pre-eclampsia, maternal Idiopathic Thrombocytopenia or IUGR secondary to placental factors. In infants whom were transfused, predominant factors included severe sepsis, especially gram-negative sepsis, Pulmonary Haemorrhage and NEC, Cytomegalovirus (CMV) infection, clinical sepsis and unknown cause. There were higher morbidities like IVH, BPD and ROP, death in transfused NT, but was not statistically significant difference. Only one infant required IVIG due to neonatal alloimmune thrombocytopenia.

Conclusions The incidence of NT was 0.014%, is higher at 29% in VLBW cohort and 28% of preterm born with GA of <32 Weeks. The significant maternal risk were pre-eclampsia and maternal thrombocytopenia. The significant Neonatal risk factors were asphyxia, lower GA, birth weight, SGA. In infants with thrombocytopenia that were severe and transfused, additional causes included severe sepsis, especially gram-negative sepsis, NEC and CMV infection