 Feedback from the mothers at the recruitment visit i.e. dating scan suggests that the mothers would have been happy to partake in the study at the same visit as receiving the PIS for 4 main reasons: 1 the study and the PIS is simple to understand; 2 they spend a significant amount of time awaiting scan and midwife appointment during this visit; 3 they want to have their blood sample taken at the same visit mothers have a blood test routinely as a standard care; and 4 they prefer not to come back for a separate visit. The investigators also believe this is reasonable as this is a non-interventional study and provides opportunity for more mothers to participate in the study. Therefore if the mother has had enough time to read and understand the PIS and provides consent, she could be recruited straightaway and blood tests done together with her routine bloods on the same day. However, if she prefers to take the PIS away and have more time to decide, the research team will see her at a future date. Such a strategy can also be replicated in the community booking visit to facilitate participation in the study. 