Ultrasound in Pregnancy

The mid-pregnancy ultrasound assessment (16 wk)

At this stage of pregnancy we can now discover much about a pregnancy:

1. Confirm gestational age. If dates, viability and number of pregnacies have not been confirmed by the 11 - 13 weeks scan (see back), they can be permed at this time. Identify abnormalities - Many abnormalities which cannot be seen can be seen at this stage, particularly the more severe abnormalities (holo 4)

2. Identify abnormalities - Many abnormalities cannot be seen at 11 - 13 weeks, so they can be identified at about 20 weeks gestation (see prenatal diagnosis).

3. Screening for Chromosomal anomalies - Our genes are carried on our chromosomes, which are in every cell in our body. The natural process is not perfect, and sometimes there are too many or too few chromosomes, leading to problems such as mental retardation (see prenatal diagnosis). The only way of being certain whether a fetus has a chromosomal anomaly or not is to perform an invasive procedure, such as amniocentesis, placental biopsy (CVS) or fetal cord blood sampling (see prenatal diagnosis).

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