Incidence and Aetiology of Thrombocytopenia in Twin Pregnancies in a Tertiary Referral Centre
Authors: Danaee Anicee , Robinson Susan , Okoli Steven , Kyle Pippa , Vieira Matias Costa , Pasupathy Dharmintra 
Published: October 2019

Abstract
Introduction
Thrombocytopenia is well described in pregnancy with an incidence of 6-10%. The majority of data with regards to platelet counts in pregnancy and aetiology of pregnancy related thrombocytopenia, however, derives from studies conducted in singletons. There is little information available on this subject in higher order pregnancies.
Aim
This longitudinal study aims to identify the incidence and aetiology of thrombocytopenia in twin pregnancies in order to guide investigation and management. As a reference we also investigate changes in platelet counts in a cohort of uncomplicated twin pregnancies from our population.
Methods
Full blood counts (FBC) and pregnancy outcome data were obtained retrospectively from electronic patient records for 676 twin pregnancies over a five year period at our institution. All women required three FBCs to be performed during their pregnancy (booking, second trimester and delivery) to be included in the study. Women with pre-existing medical co-morbidities or medication know to be associated with thrombocytopenia were excluded. A total of 381/676 women were included in the final analysis. From that original cohort, those women with uncomplicated pregnancies who delivered at term (36/40 onwards) were selected to investigate and report a reference interval for platelet count during pregnancy and compare with known reference intervals in singletons. A total of 301/676 women were included in this sub-analysis.
Results
The mean maternal age was 32.3 years with a mean gestational age of 36.7 weeks at delivery. We defined thrombocytopenia as mild: platelets 100-150 x 109/L, moderate: platelets 50-100 x 109/L and severe: platelets < 50 x 109/L. The table below summarises our results TableFull Blood countMild thrombocytopenia n (%)Moderate thrombocytopenia n (%)Severe thrombocytopenia n (%)1st FBC n=2566 (2.3%)002nd FBC n=38126 (6.8%)1 (0.3%)03rd FBC n=38177 (20.2%)12 (3.2%)1 (0.3%)
The overall rate of thrombocytopenia was 23%. The commonest cause of thrombocytopenia in this population was gestational thrombocytopenia (75%), followed by pre-eclampsia (15%) other hypertensive disorders (5.7%) and the remaining 4.3% included other complications such as sepsis and obstetric cholestasis.
The platelet ranges for our cohort of women with uncomplicated pregnancies were as shown in the table below. These results are in keeping with changes which occur in platelet counts in singleton pregnancies. TableFull Blood countMean plt count (109/L)Range95% interval1st FBC247135-390163-3262nd FBC226115-410147-3443rd FBC18526-427110-317
Conclusion
This study demonstrates that while the incidence of thrombocytopenia is double the rate in twin when compared to singleton pregnancies, the overall distribution in terms of aetiology is very similar. Interestingly this differs somewhat from data in triplet pregnancies where the majority of thrombocytopenia appears to be secondary to pre-eclampsia in one case series. This is an important finding as it indicates that like in most singleton pregnancies the majority of cases are benign and as such investigation and management pathways regarding thrombocytopenia should not differ from investigation and management in singleton pregnancies. However the increased incidence of thrombocytopenia in twin pregnancies overall requires further investigation.

Disclosures
No relevant conflicts of interest to declare.