Mr. Peter Thompson:

They will never all be diagnosed on ultrasound but some women will not present until after 24 weeks. Women who do not present until later in pregnancy tend to be those who have poorer socioeconomic backgrounds, such as those who are refugees. Generally speaking, people who are less privileged in society will present later on and have poorer pregnancy outcomes overall. If there is a gestational age limit that is lower, those women would be disadvantaged.