Ultrasound dating at 12-14 weeks of gestation. A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies.



Fetal and Obstetric Ultrasound Measurements in Pregnancy

For many women, especially after 8 weeks gestation, sufficient information about the baby may be obtained with transabdominal ultrasound only. However, in the early pregnancy, the developing embryo is very small at 6 weeks gestation, the baby is only mm long and a transvaginal ultrasound may be required to get a better image of the baby. Transvaginal ultrasound is safe and commonly performed during all stages of pregnancy, including the ultrasound dating scan measurements trimester.

It will not harm you or your baby. Transabdominal ultrasound involves scanning through your lower abdomen. A small amount of ultrasound gel is put on the skin of the lower abdomen, with the ultrasound probe then scanning through this gel. The gel helps improve contact between the probe and your skin. Transvaginal ultrasound is an internal ultrasound. It involves scanning with the ultrasound probe lying in the vagina.

Transvaginal ultrasound usually produces better and clearer images of the female pelvic organs including the developing pregnancy, because the ultrasound probe lies closer to these structures. The transvaginal ultrasound probe is thin, about 2cm diameter. The probe is covered with a disposable protective sheath. A small amount of ultrasound gel is placed on the end of this probe. The probe is then gently inserted a short distance into the vagina.

All transvaginal probes have been cleaned and sterilised according to recommended protocols. Performing the transvaginal ultrasound usually causes less discomfort than a pap smear. No analgesia is required for this ultrasound. Your privacy will always be respected during your ultrasound dating scan measurements, especially the transvaginal examination.

You will have a large towel covering your lower body, in addition to wearing a gown during the ultrasound dating scan measurements ultrasound. You will always have a choice about whether transvaginal ultrasound is performed. If you have concerns about transvaginal ultrasound, please discuss this with your sonographer before your ultrasound begins.

We usually get better images during transabdominal ultrasound if the bladder is partially filled, so to help your examination we ask you to drink water prior to the assessment. Please empty your bladder 1 hour before your appointment, drink 2 glasses of water and try not to empty your bladder again until after your appointment. A full bladder moves bowel out from the pelvis into the abdomen, helping visualisation of the pregnancy, uterus and ovaries.

Your bladder should not be so full ultrasound dating scan measurements it causes pain. If your bladder is very full ultrasound dating scan measurements painful, you should empty a small amount so you are more comfortable. You will be able to empty your bladder after the transabdominal ultrasound is completed and before the transvaginal ultrasound begins if transvaginal ultrasound is required. Sometimes the results of a first trimester scan may be inconclusive or uncertain, and need to be combined with your clinical history and blood tests serum BhCG.

Some women need to return for another ultrasound scan a few weeks oxfordshire dating sites to assess the progress of the pregnancy, or they may require another blood test serial serum BhCG. We realise this is often an anxious time for parents, while they wait for the next ultrasound to check on their baby.

We will do our best to answer your questions and minimise your anxiety. A first trimester ultrasound will usually include each of the following components however some ultrasounds may focus more on particular areas. Your ultrasound is always performed in the context of your clinical history and the results of previous ultrasounds and investigations. Before 5 weeks gestation, the developing pregnancy is too small to detect on ultrasound.

The endometrium the lining of the uterus where the pregnancy will grow should appear thick and secretory. One of the ovaries will have an ovulation cyst called a haemorrhagic corpus luteum. This ovarian cyst is a normal part of getting pregnant, as the egg forming your baby was released from this cyst. The corpus luteum will gradually resolve get smaller as the pregnancy continues. At weeks gestation, a small gestation pregnancy sac is seen within the uterus.

A transvaginal ultrasound is usually required to see the baby at this stage of the pregnancy. Your baby is just a tiny embryo. The yolk sac is the other structure that is usually identified at this early stage. The yolk sac lies within the ultrasound dating scan measurements sac and looks like a little round circle inside the pregnancy sac. Seeing a yolk sac helps the doctor confirm the presence of a developing pregnancy within the uterus, even before the embryo is seen.

This ultrasound dating scan measurements useful if there are concerns that your pregnancy may not be correctly located in the uterus an ectopic pregnancy. At weeks gestation, your baby is growing bigger and now measures mm long. From now until the end of the first trimester, the embryo will be measured from one end to the other, called the crown-rump-length or CRL. At weeks gestation, your baby continues to change appearance as it grows and develops. By 8 weeks gestation, your baby can usually be seen with transabdominal ultrasound.

By weeks gestation, the embryo is clearly recognisable as a baby with a body, head, arms and legs, as well as many other identifiable features. Your baby may be moving around the pregnancy sac. Many parents are amazed at the detail that can be seen even at this early stage of the pregnancy. First trimester ultrasound is performed in the first months of a pregnancy.

Pregnancy ultrasounds are performed mainly using transabdominal ultrasound.


Gestational Age Determination by Ultrasound