When is a dating scan necessary?
How big will my baby be at the 7 week ultrasound?
Your embryo will be measured from the top of its head, the crown to its bottom or rump . This is called the crown-rump-length (CRL). This is because it is the longest portion of the baby's body and gives an ideal measurement of baby’s growth and development.
An average length of the embryo at 7 weeks is around ¼ inch long. The average weight is less than 1 gram.
Obviously, every pregnancy is unique and individual factors influence the size of the embryo.
An average length of the embryo at 7 weeks is around ¼ inch long. The average weight is less than 1 gram.
Obviously, every pregnancy is unique and individual factors influence the size of the embryo.
How will my 7 week scan be done?
There are two ways of having a seven-week ultrasound. One is via the abdomen transabdominally, and the other is through the vagina transvaginally. At 7 weeks gestation, a transvaginal ultrasound provides the best and most accurate visualization. This is because the transducer does not need to send sound waves through multiple layers of muscle and tissue to pick up the returning images.
When a transvaginal ultrasound is done at seven weeks gestation, the transducer is placed in the mother's vagina and the sound waves are transmitted via her cervix directly into the uterus. With this form of scan, it is not as necessary for the mother to have a full bladder.
When having a transabdominal ultrasound, however, a partially full bladder is recommended. This helps to move the bowel out from the pelvis into the abdomen so the uterus, ovaries and pregnancy can be seen more clearly. Later, as the pregnancy progresses, a full bladder is not necessary as the enlarging uterus is no longer contained in the pelvic rim.
When a transvaginal ultrasound is done at seven weeks gestation, the transducer is placed in the mother's vagina and the sound waves are transmitted via her cervix directly into the uterus. With this form of scan, it is not as necessary for the mother to have a full bladder.
When having a transabdominal ultrasound, however, a partially full bladder is recommended. This helps to move the bowel out from the pelvis into the abdomen so the uterus, ovaries and pregnancy can be seen more clearly. Later, as the pregnancy progresses, a full bladder is not necessary as the enlarging uterus is no longer contained in the pelvic rim.
Why can’t I see my baby?
In very early pregnancy, the embryo and pregnancy sac may simply be too small to see very much at all. It's the shape and general structures which are more obvious. And if present, a tiny heartbeat. The average number of beats per minute (BPM) is between 100 and 180 between 6 and 7 weeks of gestation.
Am I having a boy or a girl?
At seven weeks of gestation, it is still too early to identify what sex (gender) the baby will be. It is also impossible to do a thorough fetal screening assessment because it is still just too premature in terms of embryonic development. However, general structures such as a head and body can generally be seen in the embryo at seven weeks.
Questions you sonographer may ask at your 7 week scan
- When was your last normal period, and is your cycle regular?
- How did you conceive naturally or with fertility assistance?
- What number pregnancy this is
- What is your obstetric history?
- How many (living) children you have?
- What is your medical and surgical history?
- Are you taking any medications?
- Have you had any miscarriages or pregnancy complications?
Frequently asked questions about the 7 week ultrasound
Will my dating scan tell how many babies I’m carrying?
Yes, one of the primary reasons for a dating scan at 7 weeks is to count how many gestational sacs and embryos are present.
Should my partner be with me for my 7 week scan?
If possible, yes. It is a nice experience to share. For many partners, this is the first time the pregnancy seems real.
What if they find something's wrong?
At the 7 weeks scan, only a gestational sac and yolk sac may be seen. It's still very early in the pregnancy. If there are concerns, you may be asked to return for another scan in 7 to 10 days to check on the embryo's development.
Yes, one of the primary reasons for a dating scan at 7 weeks is to count how many gestational sacs and embryos are present.
Should my partner be with me for my 7 week scan?
If possible, yes. It is a nice experience to share. For many partners, this is the first time the pregnancy seems real.
What if they find something's wrong?
At the 7 weeks scan, only a gestational sac and yolk sac may be seen. It's still very early in the pregnancy. If there are concerns, you may be asked to return for another scan in 7 to 10 days to check on the embryo's development.
The information of this article has been reviewed by nursing experts of the Association of Women’s Health, Obstetric, & Neonatal Nurses (AWHONN). The content should not substitute medical advice from your personal healthcare provider. Please consult your healthcare provider for recommendations/diagnosis or treatment. For more advice from AWHONN nurses, visit Healthy Mom&Baby at health4mom.org.
