First trimester screening is increasingly becoming available in most obstetric units in the UK. It offers an opportunity for screening and diagnosis before the pregnancy becomes obvious to others. Where there is the need to terminate the pregnancy, surgery is an option. For most women, it will enable the identiﬁcation of those at risk for whom more targeted screening and diagnostic testing could then be offered. The other advantage of screening in the ﬁrst trimester is its application in pregnancies of higher order where traditional biochemical screening is unreliable. Where invasive testing (such as CVS) is required, this can be easily undertaken.