The combined incidence of classical Philadelphia-negative myeloproliferative neoplasm (MPN) is 6-9/100 000 with a peak frequency between 50 and 70 years. MPN is less frequent in women of reproductive age. However, for essential thrombocythaemia (ET) in particular there is a second peak in women of reproductive age and 15% of polycythaemia vera (PV) patients are less than 40 years of age at the time of diagnosis. Thus these diseases are encountered in women of reproductive potential and may be diagnosed in pregnancy or in women being investigated for recurrent pregnancy loss. The incidence of MPN pregnancies is 3Á2/100 000 maternities per year in the UK. The majority of data regarding Philadelphia-negative MPNs relates to patients with ET, for which the literature suggests significant maternal morbidity and poor fetal outcome; specifically maternal thrombosis and haemorrhage, miscarriage, pre-eclampsia, intrauterine growth restriction (IUGR), stillbirth and premature delivery as summarised in the recent systematic review and meta-analysis in Blood, 2018, 132, 3046. The literature for PV is more sparse but increasing and is concordant with ET pregnancy outcomes. The literature regarding primary myelofibrosis (PMF) is even more scarce. Treatment options include aspirin, venesection, low molecular weight heparin (LMWH) and cytoreductive therapy. Data and management recommendations are often extrapolated from other pro-thrombotic conditions or from ET to PV and PMF. Women of reproductive age with a diagnosis of MPN should receive information and assurance regarding management and outcome of future pregnancies. From pre-conceptual planning to the post-partum period, women should have access to joint care from an obstetrician with experience of high-risk pregnancies and a haematologist in a multidisciplinary setting. This paper provides an update with regards to Philadelphia-negative MPN in pregnancy, details local practise in an internationally recognised centre for patients with MPN and outlines a future research strategy.There are no randomised controlled trials of MPN in pregnancy. A national prospective study of maternal and fetal outcomes of pregnant women with a diagnosis of MPN was undertaken via the United Kingdom Obstetric Surveillance System (UKOSS) between January 2010 and December 2012 (Alimam et al., 2016). The study suggests that the incidence of MPN pregnancies is 3Á2/100 000 maternities per year in the UK, i.e. 24 pregnancies per year in the UK. The UKOSS study reported 58 women with a diagnosis of MPN who were pregnant; 47 (81%) essential thrombocythaemia (ET), five (9%) polycythaemia vera (PV), five (9%) primary myelofibrosis (PMF) and one (2%) MPN-unclassified. There were 58 live births. The incidence of miscarriage was 1Á7/100 [95% confidence interval (CI) 0Á04-9Á24] and the perinatal mortality rate was 17/1000 (95% CI, 0Á44-92Á36) live and stillbirths. Incidence of maternal complications was 9% (5/ 57) pre-eclampsia, 9% (5/57) post-partum haemorrhage and 3Á5% (2/57) post-partum haematoma. There wer...