1

1

Sonography in the First Trimester

G. William Shepherd PhD, RDMS, RVT

2

Basic Embryology

1mm

Sac

3

Embryonic Timeline

Ovulation: Day 14-16

Fertilization: Day 14-16

Zygote to Morula: Day 16-18

Morula to Blastocyst: Day 18-19

Implantation: Day 19-20

Week 3

4

Embryology Terms

Gamete --------- Before fertilization

Zygote ---------- After fertilization

Morula --------- 16 -32 Cells (18 Days)

Blastocyst ---------- 20 Days

Embryonic Disc --- 28 Days

Ultrasound Detection --- 31 Days

Earliest Heart Beat ------ 36 Days

5

Yolk Sac Formation: 4w1d

6

Goals for a 1st Trimester Scan

Visualization and localization of the

gestational sac

Determination of viability

Determination of the # of embryos & viability

Estimation of gestational age

Determination of any detectable anomalies

2

7

4W6D

8

Earliest Definite Ultrasound Visualization: 31days

Pre-embryonic (embryonic disc stage 4w4d or 32days)

coronal

9

“Double Sac” Sign

10

11

“Double Sac” Sign

12 Video Clip

3

13

Age in Days (by LMP) = (L+W+H)

3 + 30

Estimation of Gestational Age

from the MSD (mean sac diameter)

14

5 weeks by LMP

15

5w0d by LMP

6mm

4mm

Width (from trv image) = 6

6+6+4 divided by 3 = 5.3, +30 = 35.3d or 5w

1cm

16

x x

+

+

xx 13mm

++ 11mm

Width 15mm MSD 13 = 43d =6w1d

5 weeks 6 days by LMP

9.25

17

Human Chorionic Gonadotropin

Made by trophoblastic cells

Detectable after implantation

Doubling time every 2-3 days

Correlates well with embryonic and sac size

Level maximizes at about 8 weeks

Max level is about 50,000 -100,000 IU/L

Declines after 10-12 weeks

18

Beta Chorionic Gonadotropin Levels

MSD Age (weeks) HCG Level

2mm 5.0 1,164

5mm 5.4 1,932

10mm 6.0 4,478

15mm 6.6 10,379

20mm 7.3 24,060 * Filly, in Ultrasonography in Obstetrics and Gynecology, ed Callen, W.B. Saunders, Philadelphia, 1994.

CRL

4

19

x x

4-5mm

20

Embryonic Timeline

Week 6: Heartbeat will be detectable during this week.

This is the neural tube stage

Weeks 6-10: Essentially all of the tissues and organs

of the embryo will form during this period.

Week 11: All of the organs are present and all but a

portion of the bowel and the external genitalia are in

their final positions.

Week 12: The bowel will reenter the fetal abdomen.

21

5w5d 6w1d

3 days development and growth 22

CRL and Gestational Age

CRL Gest. Age CRL Gest. Age

2mm 5.7 weeks 60mm 12.5 weeks

4 6.1 70 13.2

8 6.7 80 14.0

10 7.2 90 14.9

15 7.9 100 15.9

20 8.6 110 16.9

25 9.2 130 17.9

30 9.9

40 10.9 Hadlock et al

50 11.7 Radiology 18: 501, 1992

23

Yolk sac and the Early Embryo

24

6w3d

2mm

5

25

Embryonic Period 8w

Fluid?

26

CRL = 18mm 8w3d

Fluid?

Oblique Scanning Plane

27

13mm

7w2d

28

Don’t include the yolk sac in the CRL

29 30

Be aware of fetal position

6

31 32

6w1d 7w4d

8w4d 10w3d

33

After 13 weeks use BPD, HC, AC, and FL

34

Manipulation of Transducer for CRL

Video Clip

35

8w2d 9w3d

Skeletal Development

36

10w3d

7

37

Indications for a First Trimester Scan

Vaginal bleeding

Size and date discrepancy

No heart tones

Pelvic pain

Accurate dating for future C-section

History of an anomaly

Trauma

38

Significance of the Yolk Sac

Earliest landmark in the early gestational sac

Identifies an IUP

Helps to locate the embryo and heart beat

Should be round and “cystic” 3-6mm

1 yolk sac per embryo, can help identify

monoamnionic twins

Should disappear by 12 weeks

39

7 Week Embryo

40

7 Week Embryo

Amnion

Yolk Sac

Amniotic Fluid Chorionic Fluid

41

Yolk Sac

42

Yolk Sac

Too big

1 cm

1.5 cm

8

43

Compressed Yolk Sac

44

Vaginal Bleeding (1st Trimester)

Implantation Bleed

Abortion

Subchorionic Hemorrhage

Placental Previa

Ectopic Pregnancy

Blighted Ovum

45

Implantation Bleed

Most common cause of 1st trimester

vaginal bleeding

Generally not significant

Sonolucent area between the chorion

and uterus (near the internal os)

46

The future Jen Shepherd

47

Vaginal Bleeding (1st Trimester)

Implantation Bleed

Subchorionic Hemorrhage

Abortion

Placental Previa

Ectopic Pregnancy

Blighted Ovum

48

Subchorionic Bleeds

Can be behind the placenta

Can be behind the chorion lavae

Can be behind the chorionic plate of the placenta

Prognosis depends upon the cause and how much

of the placenta is involved: >1/3 prognosis worsens

9

49 50

1/4 of placenta is separated from uterus

51 52

8w2d

53

Vaginal Bleeding: 1st Trimester Implantation Bleed

Subchorionic Hemorrhage

Blighted Ovum

Placental Previa

Ectopic Pregnancy

Abortion

54

Blighted Ovum: Arrested or absent development of

the embryonic pole (trophoblasts develop)

10

55

No embryo

or Yolk Sac

56

Growth will fall off

HCG will level off

Sac may move

toward Cx

57

Trophoblastic ring

may become irregular

and thin < 2mm

58

Video Clip

59

Vaginal Bleeding: 1st Trimester

Implantation Bleed

Abortion

Subchorionic Hemorrhage

Placental Previa

Ectopic Pregnancy

Blighted Ovum

60

Placenta Previa

12w2d

11

61

Vaginal Bleeding: 1st Trimester

Implantation Bleed

Abortion

Subchorionic Hemorrhage

Placental Previa

Ectopic Pregnancy

Blighted Ovum

62

Glossary of 1st Trimester Terms

Abortion: Premature expulsion of the gestation

from the uterus

Incomplete Abortion: The expulsion of only a

portion of the gestational products from the uterus

63

Inevitable Abortion

64

Retained Products of Conception

65

Findings for Embryonic Demise

Old Criteria

The Findings Below Depend upon Body Habitus

and Type of Transducer, Endovag or transabd

No Sac Growth on Serial Exams

No Cardiac Pulsations in a 5mm Embryo

No Embryo Seen in a Sac 25mm MSD

No Yolk Sac Seen in a 20mm MSD Sac

Trophoblastic Ring is not Intact

66

Findings for Embryonic Demise

No Sac Growth on Serial Exams

A 7 -10 day interval between scans is

recommended

Give the embryo a chance

EV scanning is always best

Abdallah et al US Obstet & Gynecol 2011

12

67

The Gestational Sac Grows about 1mm/Day

1 Week Should Give a Statistically Significant Increase in MSD

MSD = 3mm MSD = 10mm

Jan 4 Jan 11

68

Findings for Embryonic Demise Slow Cardiac Pulsations in a 5 (now 7) mm Embryo in an

endovaginal ultrasound examination

69

Reading an M-Mode

1 second

Heart rate only 60 bpm Heart rate 160 bpm

1 second

70

Findings for Embryonic Demise No Cardiac Pulsations in a 9mm Embryo in a

transabdominal ultrasound examination

M-Mode No Heart-beat

71 72

13

73 74

Video Clips

75

Video Clips

76

Video Clips

77 78

Findings for Embryonic Demise No Embryo Seen in a Sac 18 (now 25) mm MSD in an

endovaginal ultrasound examination

14

79

Findings for Embryonic Demise

No Embryo Seen in a Sac 25mm MSD in an

transabdominal or EV ultrasound examination

Was 20mm

80

Findings for Embryonic Demise No Yolk Sac Seen in a 10mm MSD Gestational Sac

with endovaginal scanning

81

Findings for Embryonic Demise No Yolk Sac Seen in a 20mm

MSD Gestational Sac with

transabdominal scanning

MSD 25mm

10.0 82

New Criteria for Embryonic Demise

No Sac Growth on Serial Exams

No Cardiac Pulsations in a 7 mm Embryo*

No Cardiac Pulsations in a 9mm Embryo **

No Embryo Seen in a Sac 25 mm MSD*

No Embryo Seen in a Sac 25mm MSD**

No Yolk Sac Seen in a 10mm MSD Sac *

No Yolk Sac Seen in a 20mm MSD Sac**

* endovaginal scanning ** transabdominal scan

83

Small for Dates

Normal Pregnancy / Wrong Dates

Anembryonic Pregnancy (blighted ovum)

Ectopic Pregnancy

Fetal Demise

Oligohydramnios

Intrauterine Growth Retardation (IUGR)

84

Anembryonic Pregnancy

Embryonic Demise

S < D

Oligohydramnios

Ectopic Pregnancy

15

85

Ectopic Pregnancy 95% occur in the tube

5% are interstitial and

are the most dangerous

Cornual and cervical

ectopics are increasing

In vitro procedures

increase the chance of

ectopic pregnancy

Heterotopic: IUP plus

an ectopic

86

Transabdominal scans

Endovaginal scans

Pseudo-sac

Pseudo-sac

87

Ruptured Ectopic

88 Live Ectopic Pregnancy in Right Fallopian Tube

89

Cervical Ectopic Pregnancy

90

Ectopic Pregnancy in Right Cornu

16

91

Ectopic?

Uterus?

92

Right & Left Horns of

Bicornuate Uterus

93

Hemorrhagic Corpus Luteum Can Look Like an Ectopic

94

95

Molar Pregnancy

Large for Dates

Vaginal Bleeding

Very High HCG

May be a live embryo

1 in 1200 pregnancies in the USA

Risk is 20-40 fold higher if patient had a previous molar pregnancy (1 in 30-60)

96

17

97

There may or may not be a sac.

98

Theca Lutein Cysts

99

The arrow heads point to the major portion of the mole.

The white arrows point to echogenic invasive villi that extent

almost to the serosal surface of the uterus (black arrows).

100

Partial Mole at 12 weeks -Top, 14 weeks - Bottom

101

Video Clip

102

Large for Dates

Normal Pregnancy / Wrong Dates

Molar Pregnancy

Gestation with Mass / Masses

Multiple Gestation

10.25

18

103

Bicornuate Uterus

IUP

104

Hydatidiform Mole Theca Lutien Cysts

105

Early Pregnancy with a Mass

106

Multiple Gestation

107

Video Clip

108

2

Bleeds

Triplets

3

1

19

109

A

B

C D

E

110

Anomalies: Detectable in the 1st Trimester (Endovaginal Scanning is Best)

Anencephaly

Acrania

Cystic hygroma

Hydrops

Conjoined twins

Large omphalocele

Severe gastroschisis

Thanatophoric dwarf

111

Normal Head at 12 Weeks

Transverse Head at 12 Weeks

Choriod Plexus

Frontal

Occipital

112

Video Clip

113

Acrania at 10w2d

114

Normal Nuchal Translucency 10w6d

2mm

20

115

Normal Herniation of the Gut

into the Base of the Cord at 11w2d

116

Omphalocele

12w4d

117

Questions?