Sue Higgins and Brenda Wells are both pregnant, and at increased risk of having a Down's Syndrome child. At Guy's Hospital, they're told about a new way of detecting abnormalities only eight weeks into their pregnancy, rather than the 18 weeks of the standard test.

Which test they have will not be decided on medical grounds, but at random by computer. What unknown risks might they be submitting their babies to? Shouldn't they be allowed to choose which test to have? Why isn't the new one available to all?
"Horizon" investigates why such lotteries are necessary, and why they pose painful dilemmas for the doctors and patients involved.