PRENATAL DIAGNOSIS Prenat Diagn 2004; 24: 224–226. Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/pd.791 Maternal serum and amniotic fluid levels of macrophage inhibitory cytokine 1 in Down syndrome and chromosomally normal pregnancies Euan M. Wallace 1 *, Budi Marjono 1 , David A. Brown 2 , Jennifer Crossley 3 , Stephen Tong 1 , David Aitken 3 and Sam Breit 2 1 Department of Obstetrics and Gynaecology, Monash University, Monash Medical Centre, Clayton, Victoria 2 Centre for Immunology, St. Vincent’s Hospital and University of New South Wales, Sydney, New South Wales, Australia 3 Institute of Medical Genetics, Yorkhill, Glasgow, Scotland Objectives To measure maternal serum and amniotic fluid levels of macrophage inhibitory cytokine-1 (MIC- 1) in Down syndrome and normal pregnancies, assessing the utility of MIC-1 as a prenatal marker of Down syndrome. Methods Stored serum from 64 Down syndrome and 399 control pregnancies, collected at 8 to 17 weeks of pregnancy, and stored amniotic fluid from 17 Down syndrome and 53 controls, collected at 15 to 19 weeks of pregnancy, were retrieved for analysis. MIC-1 was measured using an established in-house ELISA, blinded to sample type. Results In maternal serum, MIC-1 levels are not altered in Down syndrome in either the first or second trimester. Levels, expressed as median (95% CI) multiples of the median (MoM), in the Down syndrome cases and controls were 1.07 (0.9–1.1) MoM and 1.0 (0.95–1.03) MoM respectively. In amniotic fluid, MIC-1 levels were significantly decreased compared to controls, 0.52 (0.44–0.64) MoM versus 1.0 (0.85–1.08) MoM (p < 0.0001). Conclusion MIC-1 is decreased in amniotic fluid but not in maternal serum in Down syndrome pregnancies. MIC-1 will not be useful as a prenatal marker of Down syndrome. Copyright  2004 John Wiley & Sons, Ltd. KEY WORDS: Down syndrome; pregnancy; macrophage inhibitory cytokine-1; amniotic fluid INTRODUCTION Macrophage inhibitory cytokine-1 (MIC-1) is a diver- gent member of the transforming growth factor-β fam- ily, originally cloned and characterised from activated macrophages (Bootcov et al., 1997). Subsequently, it was shown that the human placenta also abundantly expresses MIC-1 mRNA (Lawton et al., 1997; Fair- lie et al., 1999) and that MIC-1 protein is present in the placenta, maternal circulation and amniotic fluid (Moore et al., 2000). Similar to other members of the TGF-β superfamily, such as inhibin and activin, MIC-1 is immunolocalised to the syncytiotrophoblast in early pregnancy (Marjono et al., 2003). The ontogeny of MIC-1 in the maternal circulation across pregnancy is also similar to that of inhibin and activin with levels increasing to a maximum at term (Moore et al., 2000; Marjono et al., 2003). In view of these similarities and because inhibin A is a useful prenatal marker of Down syndrome (Wallace et al., 1995; Aitken et al., 1996), we undertook this *Correspondence to: Euan M. Wallace, Associate Professor, Centre for Women’s Health Research, Department of Obstetrics and Gynaecology, Monash University, Monash Medical Centre, 246 Clayton Road, Clayton, Victoria, 3168, Australia. E-mail: euan.wallace@med.monash.edu.au study to explore whether MIC-1 might also be a marker of Down syndrome. METHODS Stored serum, which had been prospectively collected as part of two Down syndrome screening programmes, from 64 women with a Down syndrome fetus and from 399 women with a chromosomally normal singleton fetus was retrieved for analysis. The chromosomally normal controls were matched with cases for source (Glasgow or Melbourne), gestation (completed week of pregnancy) and duration of storage (within a year). Amniotic fluid from 17 Down syndrome pregnancies and 53 chromosomally normal pregnancies, matched for gestation and duration of storage, was retrieved from storage for analysis. The amniotic fluid had been col- lected and stored at −20 ◦ C prospectively at Monash Medical Centre as a component of the prenatal diag- nostic service. All amniocenteses had been performed for advanced maternal age. It had been separated for storage from fetal epithelial squamous cells by cen- trifugation at 250 × g either on the day of collection or on the following day. Storage of amniotic fluid for subsequent research is undertaken with the approval of Monash Medical Centre Human Research and Ethics Copyright  2004 John Wiley & Sons, Ltd. Received: 7 July 2003 Revised: 12 October 2003 Accepted: 24 October 2003