9 Week Ultrasound

The 9th week of gestation is the beginning of the third month of your pregnancy. At this time, the doctor will propound an ultrasound, to determine the duration of the pregnancy more accurately and to see the condition of the uterus and fetus. Also, he can estimate the development of the baby’s organs and possible malformations.

About Obstetric Ultrasound

Obstetric ultrasound is used for getting the image of the moving fetus on a monitor screen. The frequency of the ultrasound waves is between 3.5 to 7.0 megahertz. They are emitted from a device called transducer. The transducer is then placed on the skin of your abdomen. Repetitive arrays of the ultrasound beam to the uterus and scan the fetus in thin slices and are reflected back onto the same transducer. From the images displayed on the screen, we can measure baby’s development and inspect fetal heartbeat and possible malformations.

Measuring CRL allows us to get an accurate estimation of the gestational age. It is the length from the crown to the rump (the Crown-Rump Length). At the time of 9-weeks, it is about 2-3 cm.

Yolk Sac

The yolk sac is the primary source for an exchange of the nutrition between you and your baby. Therefore, it is important to measure the yolk sac diameter before placental circulation is established. Between 7 and 11 weeks of pregnancy, the yolk sac can reach a diameter up to 7 mm. After that period, it will decrease in size. But, there are cases where the diameter of the yolk sac is greater than 5.6 mm before the 10th week, which might be associated with an abnormal fetal development.

With an ultrasound, we can inspect localization of the placenta, its condition, and possible abnormalities, existence of multiple pregnancies and their growth. Decreased or excessive amount of amniotic fluid is clearly visible by ultrasound.

Using the ultrasound, your sonographer can diagnose intrauterine death, ectopic pregnancy, uterine and pelvic abnormalities. There are also other diagnostic procedures for prenatal diagnostic such as amniocentesis and chorionic villus sampling.

Preparation for An Ultrasound

Obstetric ultrasound is a safe, accurate, cost-effective and non-invasive method of examination. During the examination, the only discomfort felt is a pressure on your bladder which must be full, if it is early trans-abdominal ultrasound. If you are prepared for a trans-vaginal ultrasound, then you will have an empty bladder. It is an internal method using a transducer which will be placed into your vagina during the examination. The diameter of the trans-vaginal transducer is about 2 cm, so you will not sense any discomfort.

About the Baby’s Development


Around 9 weeks of pregnancy, your baby has grown to about 2-3 cm (CRL), weights around 2 g and the fetal sac is 3 cm. He/she is prepared for a period of fast growth. The fetal sac is approximately the size of 3 cm.

The placenta is developed enough to supply baby’s blood with oxygen and nutrients from your blood, as well as to get rid of the waste products. It is also now able to start with the production of hormones.

The major internal organs are continuing with the development. The heart has already divided. Now it comprises 4 chambers and you can hear your baby’s heartbeat on a Doppler device. It beats about 130-150 per minute.


The brain of a fetus has already divided into two hemispheres. The cerebellum, which is responsible for the coordination of the body movements, starts to form. Nerves and spinal cord follow the development of other organs.

The whole baby’s body is being formed around this time. The muscles and cartilages are growing. The arms are developing faster and can bend at the elbows. The legs with the wrists and ankles are well formed. The places on the hands and feet, where the toes and fingers will form, now are marked. He/she starts to move his/her legs and arms. Now, these movements are more and more coordinated. The fetus is too small for you to feel it moving, but all of this you can see on the ultrasound screen.

3Here you can clearly see the baby and the umbilical cord that connects it to the yolk sac.

All of the organs rapidly continue to prepare for life outside the womb. The face is slowly forming. Eyelids cover the eyes completely. They are fused and will not open until the 26th week. Eyes are more prominent and the pigment is being produced. You can see the tip of the nose, as well as small earlobes. His/her hair follicles are starting to form. The mouth, lips, and forehead also continue to grow and distinguish, while the teeth start to develop as well. Baby’s tongue is also developing with tiny taste buds. Bulb-shaped buds are formed inside the gums. They will become milk teeth, soon.

Genitals are also starting to develop, although it is still too early to define the sex of your baby by ultrasound.

Ultrasound at the 9th week is really exciting part of your pregnancy since you can see your baby’s development and its forming into a human being.

Possible Complications

Baby is growing inside your stomach, so the uterus expands and enables the baby’s progress. This is a process that may cause some pain and discomfort, especially at the time of the first pregnancy. Maybe you’ll feel a slight pain in your back. This is a result of the pressing of the uterus on the lower spine. You can feel it as an occasional sharp pain in the lower back which descends along the thigh. This occurs if the uterus is pressing the nerve, so the pain will be prominent in the thigh area. However, if the cramps during the 9th week are persistent, strong, are lasting several days, or if you are having a vaginal bleeding, you have to see a physician. In this case, you are at a high risk of miscarriage. About 40% of fetal abnormalities are incompatible with life. Some can cause bleeding. Your practitioner might see it by ultrasound, so he could take certain steps to prevent the condition from getting worse.


Prenatal diagnosis of a mole can be misdiagnosed with non-identical twin pregnancy by ultrasound scan at 9 weeks of gestation. There is an empty shriveled and wrinkled gestational sac. It appears almost completely filled by a thickened placental ring (showed with an arrow).


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