Dating ultrasound for amnio

Amniocentesis is usually performed between 14 and 20 weeks.

Some medical facilities may perform amniocentesis as early as 11 weeks.

Twins account for about 1% of all pregnancies with two-thirds being dizygotic and one-third monozygotic (identical).

This is to assess your chance of having a baby with these conditions. Edwards' syndrome is also called Trisomy 18 or T18, and Patau's syndrome is also called Trisomy 13 or T13.

Chromosomes carry the genes that determine how we develop. Problems can occur when sperm or egg cells are produced, which can lead to a baby having an extra chromosome. In Down's syndrome, there is an extra copy of chromosome 21 in each cell.

A baby born with Down's syndrome will have a learning disability.

This is thought to be because fetal membranes were first described in sheep.

Diagnostic ultrasound in the first trimester deals with pregnancy dating, the recognition of early pregnancy failure/loss (embryonic demise, spontaneous abortion, ectopic pregnancy, placental abnormalities), multiple pregnancy and with the recognition of normal anatomy and/or the detection of anomalies in very early viable pregnancies.