Ultrasounds

FAQ

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This is a compilation of questions asked concerning ultrasounds.

Question:
I am 7 weeks pregnant. Yesterday I went for a scan yesterday and was told that I needed to have a full bladder. I was made to drink 4 cups of water and my bladder was almost bursting at the end of the session. Is this really necessary ?

Answer:
In the early stages of pregnancy, a full bladder is usually required when the scan is done abdominally. This tends to lift the uterus up a little bit and being pushes the bowels away acting as an echo-lucent window for the ultrasound to pass through. Ultrasounds won’t pass easily through air (as in the bowels) but transmits perfectly through liquid (as in the case of the urine in the bladder). It will be much easier for your ultrasound technologist to see things more clearly with a full bladder, especially the presence or absence of fetal heart beat. However a full bladder isn’t needed in a vaginal scan.

sonograms

More Ultrasounds FAQ

Question:
I pregnant for 6 weeks and 5 days pregnant, I arrive for a 3d ultrasound scan today but I was told that the fetus couldn’t be seen. They said this could be because of my irregular menstruation, and asked me to return for another scan next week. What does that mean? I am quite concerned.

Answer:
Usually the fetal heart beat can be seen quite clearly by about 6 and a half weeks, particularly in a vaginal ultrasounds scan. By 6 1/2 weeks we mean 6 1/2 weeks from the last menstrual period (LMP), rather than 6 1/2 weeks from the date of conception ( which is of course around the day of ovulation ). In women with irregular and slightly longish cycles (say, 35 days verses a usual 28 days), the day of ovulation would actually be postponed to 1 week on top of the 14 days in the usual case, that is, she ovulates on Day 21.

The number of days between the first day of menstruation and the date of ovulation (the follicular phase) varies, however the number of days between ovulation and the start of the next menses (the luteal phase) is usually rather consistent at about 14 days. So if you have a menstrual cycle of 42 days, then you will ovulate on Day 28! Add 14 days and your next menses will arrive. Therefore if you have a longish cycle then you ovulate late and your fetus will not be as advanced as it should be, meaning it will appear smaller or even not visible at all.

Of course, if for some other reason, the fetus has not developed, then it will also show up smaller. In order to make a correct diagnosis a repeat a scan is required in about a week's time, so that those who are smaller because of a date factor will then be found to have grown.

Question:
I am seven weeks pregnant and went for a scan yesterday. My doctor said everything looks fine and the heart beat was visible. He said that the chances of miscarrying are small and he looked quite confident when he said that. Is this a valid comment?

Answer:
Most obstetricians now believe that the majority of first trimester miscarriages are caused by a defect in the embryo, and are basically a chance event. Imagine a sperm joining with an egg and developing into a fetus. This process involves many millions of cell divisions and changes so that the chance of something going wrong is quite high. If it happens very early on in development, for example 4 to 5 weeks, the growth of the embryo may come to a halt. The heart will stop beating. In due course the body rejects the non-viable material, commencing the process of 'miscarriage'. So if by about 7 or 8 weeks, all appears intact with a good strong heart beat, it is quite reasonable to believe that the pregnancy will continue. (The statistics are actually on an average better that 95%, although it will be lower in women with recurrent miscarriages).

Question:
My wife is 9 weeks pregnant with twins, she has had bleeding on and off and spotting for the past 3 weeks. She previously had three ultrasounds, all of which have shown 2 fetal heartbeats. We are concerned because of the spotting and bleeding which leads me to ask two 2 questions:

1. What are the main known causes of spotting and bleeding?

2. Given "positive" ultrasounds, how does that sit with the fact that there has been occasional spotting and bleeding?

Answer:
It is always hard to determine the exact cause of bleeding in the first trimester of pregnancy. With your wife, it could just be bleeding from the cervix or the edge of the placenta (which is bigger and closer to the cervix due to the twin pregnancy) and these circumstances usually bear little or no significance. From time to time the bleeding can continue until the second trimester. If there is a heartbeat present, it remains true that over 97% of the time the pregnancy will continue problem free.

Traditionally, any vaginal bleeding during early stages of pregnancy was known as 'threatened abortion'. With the birth of ultrasound, we have to say that this is a misnomer, as in the cases when the fetal heartbeat is visible, the pregnancy is not ' threatened '.

Question:
I had a scan yesterday and am about 30 weeks pregnant. My doctor said that there is too little fluid around the fetus and told me to take more rest. He seemed to look worried. Is this serious?

Answer:
A decrease in the amount of fluid around the fetus can be normal in majority of cases, and can apparently be improved with more rest, which in turn improves the circulation to the uterus.

A large decrease in the amount of liquor is associated with retarded growth of the fetus and possible other malformations. Your doctor probably looked concerned because he may be unsure as to whether the fetus is suffering from an abnormality. In a case such as this, referral to a center with expertise in ultrasounds scanning for fetal malformations may be needed.

However please remember, most cases will be quite normal and bed rest with improve the situation. The amount of liquor around the fetus is not linked with the size of the mother or how much water she is drinking each day.

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