Midwife Nikki replies: This fairly common finding appears on an antenatal scan as black spots on one or both of your baby's kidneys.

It indicates a build-up of fluid due to an obstruction in the flow of urine. But as the tubes from your baby's bladder grow, the urine will flow more easily, so when your baby is re-scanned at 34 weeks the kidneys may be normal.

If the scan reveals there is still some increased fluid, your baby will need another scan after birth and may be given antibiotics for the first few months to prevent a urine infection.

Early diagnosis means your baby will be treated quickly.