Published April 01, 2008 by
Since the 1970s, remarkable improvements in ultrasound technology have opened a real "window on the womb." Ultrasound consists of high-frequency sound waves that are bounced off the baby to give a photographic picture of the fetus. Unlike X-rays, which have much higher powers of penetration, ultrasound will identify soft tissues. Thus, it can give a complete picture of the growing baby and is a very useful diagnostic tool.
An ultrasound scan may be used to date the pregnancy, and thereafter used as needed in hospitals with the equipment. If not, women who may be at special risk because of problems with a previous pregnancy, or who would like to have a scan, can often be referred to a hospital where it can be performed. The pregnancy can be very accurately dated at around 16 weeks by measuring the circumference of the baby’s head. This knowledge is useful in avoiding problems later if the mother is unsure of her dates and does not know when the baby is due.
The scan can locate the position of the placenta, which can be helpful if there is any bleeding later in pregnancy, and it can be used to check that the baby has no major physical abnormalities such as anencephaly. Ultrasound can show congenital heart defects, kidney disease and other severe abnormalities. Ultrasound can also detect if the mother is expecting more than one baby.
There has been some controversy about the safety of ultrasound, which has concerned some women. They are not sure whether they should accept a scan. Ultrasound has now been in use for many years without any evidence of harmful effects to the baby. All indications are that the benefits of having ultrasound outweigh any potential risk. Not least is the benefit of reassurance given to many women on seeing their baby is alive and well, particularly those who have waited a long time to have a baby or who have experienced a miscarriage. However, a large study carried out in the United States by the National Institutes of Health on 15,000 women with a low risk of problems in pregnancy showed that while detection of twins and malformations was increased, and pregnancy could be dated more accurately, the outcome-in terms of healthy babies-was not improved when ultrasound was employed. There was no difference in the rate of fetal or neonatal death or subsequent illness. Rates for preterm births, for the outcomes of postdate pregnancies and for low-birth-weight babies were similar for those who had had ultrasound and those who had not. Although the percentage of abnormal fetuses detected in the group who had ultrasound was three times higher, the termination rate was about the same in both groups.
So, while ultrasound is of undoubted benefit to women at high risk or in special situations where a problem is detected, its routine benefits are unproved for now. Ultrasound can help some mothers anxious about their pregnancies by reassuring them, but can also create anxieties for others: "Towards the end of my pregnancy they started to worry about whether my baby was growing as he should. I don’t know what started it, but once they got this idea into their heads they wouldn’t leave me alone. I was in and out of the hospital having my blood pressure taken and having ultrasound scan after scan. My blood pressure was up-with worry, no doubt-and they couldn’t decide what to do. They said they would have to induce the baby early to make sure that all would be well. Then they changed their minds and decided to wait. I was in the hospital for the last few weeks of the pregnancy and, of course, the baby decided to be late. I was two weeks overdue before they decided induce the birth. By then I was so desperate I said, ‘Yes.’ It was a terrible birth, ending with an emergency Cesarean, and when he was born he was 7 pounds, 1 ounce. He didn’t look overdue. I asked my doctor later, ‘So what happened with this small baby?’ There was nothing wrong at all! My worries were for nothing. They said they couldn’t explain it but he had appeared small on the scan. So much for all their wonderful technology!" Some women-and doctors and midwives, too-feel that, with the increased reliance on new technology, many of the old skills in obstetrics are being lost: "I had shared care and I noticed a tremendous difference between my visits to the well-baby clinic and my visits to my very experienced doctor. At the clinic, people seemed to poke and probe for a long time and suggested that I have another scan to see the baby was growing OK. When I went to my doctor, she examined me very quickly and said, ‘Oh, this baby’s doing fine, I think he weighs about 4 pounds now.’ I asked how she knew and she just said, ‘Experience.’ In the clinic, I feel like you only see the junior staff, with the senior staff called for special occasions. No wonder you don’t always get the best care and they give you all kinds of unnecessary tests!"
Having an Ultrasound Scan.
An ultrasound scan is a simple, noninvasive procedure. In early pregnancy you are usually asked to drink a lot of water an hour or two before your appointment and not to empty your bladder. This pushes the womb up in the pelvis and will give the ultrasound operator a clearer view. You will be asked to lie down on a couch and remove any clothing that covers your abdomen. A cold gel is rubbed over the abdomen to enable the ultrasound operator to move the scanner smoothly over the area. As she does so you will see the baby’s outline appear on the television screen and you will also see the fetal movements.
It can be difficult to interpret what you are seeing, so ask if you are not told. The operator can freeze the picture at any time and point out things to you without exposing the baby to any more sound waves than necessary. You will usually be able to see the baby’s head, the arms and legs moving around, and some of the internal organs at work. You may even be able to see the baby sucking his thumb. Eventually, couples look forward to finding out the gender of their baby (and can give friends and family an idea of what types of baby gifts to look for.)
"The woman took a lot of time to explain to me what she was looking for and what she could see. I found all of it so reassuring. She pointed out the heart beating, the cord and the placenta, the kidneys and the spine and showed me how much he was moving around." Other women find the process unnerving, especially if nothing is explained. "No one said anything to me and I was afraid to ask in case anything was wrong. She kept on looking at everything and taking measurements and I started to get very jumpy. Then she suddenly got up and said, 'I just want to get a second opinion on this,’ and I was terrified. I thought, ‘This is it. Something’s really wrong.’ I was in tears. Someone else came back and they were both looking at the screen, still not saying anything to me. ‘What is it, what is wrong?’ I finally asked. ‘Nothing’s wrong, I’m just checking these measurements,’ she said. I felt as if I weren’t a person-just a scientific toy." Usually the baby’s father is welcome to come and watch the process and see the baby on the screen. Many dads find this is a very positive experience, not only because they are able to give support, but also because the baby becomes real to them in an even more dramatic way than to the woman: "It was hard for me to take in that she was pregnant until I saw the baby on the screen. It was fantastic-it made it come alive for me."
If you enjoyed this article, you might also like this post on Preparing For A New Baby: A How To Guide.