first trimester scans

First Trimester

Ultrasound Sonogram

Baby developing inside you
over the weeks and months
early pregnancy ultrasound sonogram


First Trimester Scans

The first trimester is months one, two, and three of your pregnancy.
Below are scan pictures taken during the early weeks of pregnancy. Measurements taken at these early scans will help to; confirm a pregnancy, date the pregnancy and to see any problems that may occur in the pregnancy ( low lying placenta, twins etc.).

Scans for week:  |  4  |  5  |  6  |  7  |  8  |  9  |  10  |  11  |  12  |  13  | 

early pregnancy sonogram scans
Scans in early pregnancy are usually performed in the first trimester around 12 weeks. You may have a earlier scan, if you are experiencing pain or bleeding for example or unsure of LMP dates.

Transabdominal ultrasound (TAU) and also the transvaginal ultrasound (TVU) are valuable diagnostic tools in obstetrics and gynecology.

Transabdominal ultrasound will provide a panoramic view of the abdomen and pelvis and is noninvasive, whereas transvaginal ultrasound provides a more limited pelvic view and requires insertion of a probe into the vagina.

Transabdominal ultrasound cannot reliably diagnose pregnancies that are less than 6 weeks gestation. Transvaginal ultrasound, by contrast, can detect pregnancies earlier, at approximately 4 to 5 weeks gestation. Prompt diagnosis made possible by transvaginal ultrasound can, therefore, result in earlier treatment.

It is recommended that all pregnant women have a scan in the first trimester, to establish the date when the baby is due, check the number of babies also the position of the placenta.

First trimester ultrasonic scans may show 'soft' markers for chromosomal abnormalities, such as the absence of fetal nasal bone or an increased fetal nuchal translucency (back of the neck) to enable detection of Down syndrome fetuses.

While your sonographer takes measurments they will explain what you are looking at. It may not be easy for you to make out what you are seeing on the screen in the early scans. The images below will give you an idea of what can be seen and what they look for at each week; of the first trimester.

Scans for week:
 |  4  |  5  |  6  |  7  |  8  |  9  |  10  |  11  |  12  |  13  | 

More Ultrasound Scan Information:

Fetal growth percentile charts  |  Fetal Growth Percentile Calculator

Charts and tables for: - CRL - BPD - OFD - HC - HL - FL scan measurements.


Week 4 Scan

gestational sac
Gestational Sac size = 3 to 6mm
4week doppler
At 4 weeks and 3 days, a tiny gestational sac becomes visible within the decidua.
The gestational sac first appears at about 4 weeks gestational age, and grows at a rate of about 1 mm a day through the 9th week of pregnancy.

It initially appears as a round, anechoic structure. In experienced hands, it may be detected as early as 30 days gestation by TVU.

While a gestational sac is sometimes seen as early as during the 4th week of gestation, it may not be seen until the end of the 5th week, when the serum hCG levels have risen to 2500 - 3500 mIU/mL.


Gestational Sac week 4 ultrasound scan    
At this early stage of pregnancy, the gestational sac already contains the yolk sac, embryonic disk, and amnion, but these structures are too small to be visualized by sonography.

In these early first trimester scans, when no structures are visible within the gestational sac, gestational age (GA) may be estimated from the sac diameter. A common method is to measure the mean sac diameter (MSD), add 30 to the sac size in millimeters, to give gestational age in days. By the time the embryo becomes visible on ultrasound the sac diameter is no longer accurate in estimating gestational age. If cardiac activity can be detected but the embryo is not measurable, the GA is about 5.5 to 6.0 weeks.

Week 4 Fetal Development


Week 5 Scans

5weeks yolk sac
Gestational sac (black area) is seen. The yolk sac (small white circle at upper left of sac) is a source of nutrients for fetus.
 week 5 scan
Gestational Sac
size = 6 to 12mm  
The Embryo is too small to be seen early in week 5, it is smaller than a grain of rice.

5weeks 4days fraternal twins
week5 day4 mono twins
Twin pregnancy (fraternal twins) Ultrasound
Pregnancy resulted from implantation of 2 genetically different embryos.
Yolk sacs and fetal poles (the early fetus) are seen in 2 completely separate sacs
 One gestational sac seen with 2 yolk sacs visible inside it Identical (monozygotic) twins.
This results from an early embryo dividing into 2 genetically identical embryos.
Fetus = approximately 1.25 mm long

An experienced sonographer can detect a yolk sac with transvaginal ultrasound when the gestational sac has reached a mean diameter of 8 mm to 10 mm. The presence of a yolk sac confirms the diagnosis of an intrauterine pregnancy and excludes ectopic pregnancy, except in rare cases of simultaneous intrauterine and extrauterine gestations.

The yolk sac is first visible at 5 weeks and it is always present by 5 weeks and 4 days. There are lacunary structures [cavities or spaces] at the site of implantation. The embryonic pole appears adjacent to the yolk sac, soon showing cardiac activity. Since the connecting stalk is short, the embryonic pole is found near the wall.

With transvaginal ultrasonography, cardiac motion can sometimes be seen in a 2-mm to 3-mm embryo, and is invariably detected in normal pregnancy when the length of the embryo reaches 5 mm. At the end of week 5, the heart rate is about 60 90 bpm.
In early pregnancies, the actual cardiac rate is less important than its presence or absence.

Week 5 Fetal Development


Week 6 Scan

week6 ultrasound
Sac size = 14 to 25mm
CRL (crown to rump length)
= 4 to 7mm
Length = 0.2 to 0.3 inch
6 week
Close up week 6 3D scan
3D with arrows pointing to the embryo (CRL) The yolk sac lies adjacent to the embryo

6 weeks 4 days
Embryo cardiac ativity was seen with a heart rate of 126 bpm.

6w4d fetalpole
Fetus is between white cursors
A fetal heartbeat was seen during this scan

The fetal pole grows at a rate of about 1 mm a day, starting at the 6th week of gestational age. Thus, a simple and accurate way to "date the fetus" in an early pregnancy is to add the length of the fetal pole (in mm) to 6 weeks. Using this method, a fetal pole measuring 5 mm would have a gestational age of 6 weeks and 5 days.

Week 6 Fetal Development


7 Weeks Scans

With high-resolution, the heartbeat is seen as a regular flutter in the embryo, first evident at 6 weeks.
The presence of a heartbeat is seen as a very positive sign. Details of the heart anatomy are not visible, but the atrial and ventricular compartments can sometimes be distinguished by the reciprocal [alternating] movements of the walls. The heart rate increases from 130 bpm to 160 bpm.

7 weeks 4 days
2D Scan:   7 weeks + 4 days
7 weeks 5 days
7 week + 5 days   3D scan    
CRL (crown to rump length) = 5mm to 12mm Length = < 0.5 inch   Weight = < 1g = 0.02oz

Gestational age (GA) in the first trimester is usually calculated from the fetal crown-rump length (CRL). This is the longest demonstrable length of the embryo or fetus, excluding the limbs and the yolk sac.

The correlation between CRL and GA is excellent until approximately 12 weeks. No sex or race differences are appreciable, but maternal characteristics, such as age and smoking, may have a significant effect beyond 10 week gestation. The GA estimate has a 95% confidence interval of plus or minus 6 days, and it is most accurate between 7 and 10 weeks of pregnancy.

Transabdominal ultrasonography may underestimate gestational age by an average of 1.6 days compared with transvaginal ultrasonography.

Week 7 Fetal Development


8 Weeks Scan

eight week ultrasound
CRL (crown to rump length) = 16mm to 20mm
eight week scan
Length = 0.6 to 0.9 inch   Weight = 1g = 0.04oz  

week 8 sonogram
8 week 3D scan

twins ultrasound
Twins eight week ultrasound scan      
At the end of the 8th week, the elbows become obvious, the feet, hands and even the fingers maybe distinguishable. The brain cavities are easily seen as large 'holes' in the embryonic head. The heart rate has increased to 160 bpm and the heart covers about 50% of the chest area. In some cases, it is possible to recognize the fluid-filled stomach below the heart at the end of week 8.

Week 8 Fetal Development


9 Weeks Scans

During week 9, the heart rate reaches a maximum of about 175 bpm.

9 week ultrasound
9 week 3D
9 week 3D scan    
Week 9 Scan
CRL (crown to rump length)
= 20mm to 30mm
9 week scans
Length = 0.9 to 1.2 inch  
Weight = 2g = 0.07oz  

Week 9 Fetal Development


Week 10 Scan

 week ten ultrasonography
CRL = 1.2 to 1.6 inch (crown to rump length) = 31mm to 41mm

Weight = 4g = 0.14oz

Week 10 Scan

Tenth week 3D scanDoppler ultrasound is a form of ultrasonography that images and examines blood flow. The direction of blood flow is shown in different colors on the screen.Doppler ultrasound
Doppler ultrasound scan      
week10 3D
Tenth week 3D scan
twins sonogram
Twins week ten ultrasound scan      
Week 10 Fetal Development


11 Weeks Scan

Eleven week sonogram
CRL = 41mm to 54mm
11 Weeks Scan
Length = 1.6 to 2 inch   Weight = 7g = 0.25oz  

week 11 3D
week 11 3D scans

Eleven week ultrasound
Eleven week ultrasound scan      
Week 11 Fetal Development


Week 12 Scans

week 12 ultrasound
CRL= 2.2 to 2.9 inch. CRL= 41mm to 54mm
Week 12 Scan
Weight = 14g = 0.5oz   

week 12 sonogram

first ultrasound scan

The 12 weeks scan [10 weeks fetal age] above shows a very active fetus. The mother who can not feel these movements, laughs as she looks at the screen and can see her tiny baby kicking out.

The nuchal translucency (NT) 12 week scan is a routine ultrasound examination carried out at 10 to 14 weeks of gestation.

Most NT ultrasound scans reveal a healthy and normal baby, or sometimes multiples. A standard prenatal ultrasound exam usually takes about 20 - 30 minutes.

Twins sonogram scan
   Twins sonogram scan
mono amniotic twins
Twins in the same sack are referred to as    'mono amniotic twins'   

Week 12 Fetal Development


13 Weeks Scan

13 Weeks Scan
CRL= 74mm to 87mm
CRL= 2.9 to 3.4 inch
first trimester scan
  Weight = 23g = 0.8oz  

13 Week ultrascan

sonogram week13

Week 13 Fetal Development
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