OBJECTIVE: To investigate the pregnancy outcomes in a cohort of women who failed to obtain a result in non-invasive prenatal testing (NIPT).DESIGN: Historical cohort study.SETTING: A multicentre private practice in Sydney, Australia.POPULATION: Women who failed to obtain a result from NIPT (n = 131).METHODS: The maternal characteristics, antenatal investigations and pregnancy outcomes for these women were compared with those who obtained a result at the same practice and to the general Australian obstetric population.MAIN OUTCOME MEASURES: Antenatal investigations: pregnancy-associated plasma protein-A (PAPP-A), free β-human chorionic gonadotrophin (β-hCG), placental growth factor (PlGF), uterine artery pulsatility index (PI), mean arterial pressure (MAP). Pregnancy outcomes: chromosomal abnormality, pre-eclampsia, gestational diabetes, small-for-gestational-age (SGA), preterm delivery.RESULTS: Only 1.1% of NIPT samples failed to return a result. This cohort was significantly older and had significantly increased weight compared with the general Australian obstetric population. Pregnancy outcomes were available for 94% of the cohort. There were significantly higher rates of chromosomal aneuploidies (6.5% versus 0.2%, P < 0.0001), pre-eclampsia (11% versus 1.5%, P < 0.0001) and gestational diabetes (23% versus 7.5%, P < 0.0001) compared with the general obstetric population. Rates of preterm delivery and SGA were elevated but did not reach significance. Antenatal investigations demonstrated decreased PAPP-A MoM (0.75 versus 1.14, P < 0.0001), decreased free β-hCG (0.71 versus 1.01, P < 0.0001) and increased uterine artery PI (1.79 versus 1.65, P = 0.02).CONCLUSION: Women who fail to obtain a result from NIPT are at increased risk of adverse pregnancy outcomes, in particular chromosomal aneuploidy, gestational diabetes and pre-eclampsia.FUNDING: None received.TWEETABLE ABSTRACT: Women who fail to obtain a result from cell-free DNA NIPT are at increased risk of adverse pregnancy outcomes.