Ultrasound during pregnancy can be used to diagnose or screen for a number of foetal abnormalities or conditions, and also to locate the position of the placenta. It may be used early in pregnancy to get a clearer view of the uterus or ovaries if a problem is suspected, or to determine how far the pregnancy has proceeded, that is “gestational age”. In addition it can be used to see whether the pregnancy is viable, as well as whether there is only one foetus, twins or more.
Before 14 weeks, only major abnormalities can be detected, however measurement of the skin thickness at the back of the neck can be done to calculate the risk of chromosomal abnormality.
At 15 -16 weeks, the baby’s genital become obviously male or female and ultrasound at this stage can identify the sex of the baby, to about 90% accuracy. The ultrasonographer looks for penis, and if one cannot be identified, the baby is presumed to be a girl.
In general however, babies must be at least 18 weeks gestation to properly examine all their body systems, although some abnormalities are still not obvious until 22 weeks. At this stage, most organ systems can be examined to ensure that the foetus appears to be developing normally. The spine, skull, brain, heart, lungs, kidneys, arms and legs can all be seen, although the clarity is somewhat less in overweight mothers.
From 30 weeks onwards, ultrasound is often used to estimate the size of the baby, although it is difficult to be precise about this. It may be useful if the woman has had a small baby in the past or has a condition that may affect the baby's growth, such as pre-eclampsia. The bloodstream in the umbilical cord can be examined to see if it is functioning well enough to transport sufficient oxygen and nutrition to the foetus, and the amount of amniotic fluid and position of the baby is also checked.
Before 14 weeks, only major abnormalities can be detected, however measurement of the skin thickness at the back of the neck can be done to calculate the risk of chromosomal abnormality.
At 15 -16 weeks, the baby’s genital become obviously male or female and ultrasound at this stage can identify the sex of the baby, to about 90% accuracy. The ultrasonographer looks for penis, and if one cannot be identified, the baby is presumed to be a girl.
In general however, babies must be at least 18 weeks gestation to properly examine all their body systems, although some abnormalities are still not obvious until 22 weeks. At this stage, most organ systems can be examined to ensure that the foetus appears to be developing normally. The spine, skull, brain, heart, lungs, kidneys, arms and legs can all be seen, although the clarity is somewhat less in overweight mothers.
From 30 weeks onwards, ultrasound is often used to estimate the size of the baby, although it is difficult to be precise about this. It may be useful if the woman has had a small baby in the past or has a condition that may affect the baby's growth, such as pre-eclampsia. The bloodstream in the umbilical cord can be examined to see if it is functioning well enough to transport sufficient oxygen and nutrition to the foetus, and the amount of amniotic fluid and position of the baby is also checked.