Sonography in the First Trimester Basic Embryology

1mm Sac

G. William Shepherd PhD, RDMS, RVT

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Embryonic Timeline Embryology Terms

 Gamete ------Before fertilization  Ovulation: Day 14-16  Zygote ------After fertilization  Fertilization: Day 14-16  Morula ------16 -32 Cells (18 Days)  Zygote to Morula: Day 16-18 Week 3  Blastocyst ------20 Days  Morula to Blastocyst: Day 18-19  Embryonic Disc --- 28 Days  Implantation: Day 19-20  Ultrasound Detection --- 31 Days

 Earliest Heart Beat ------36 Days

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Yolk Sac Formation: 4w1d Goals for a 1st Trimester Scan

 Visualization and localization of the  Determination of viability  Determination of the # of & viability  Estimation of gestational age  Determination of any detectable anomalies

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1 Earliest Definite Ultrasound Visualization: 31days

4W6D coronal

7 Pre-embryonic (embryonic disc stage 4w4d or 32days)8

“Double Sac” Sign

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“Double Sac” Sign

Video Clip 11 12

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Estimation of Gestational Age 5 weeks by LMP from the MSD (mean sac diameter)

Age in Days (by LMP) = (L+W+H) + 30 3

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5w0d by LMP 5 weeks 6 days by LMP

1cm 4mm + x x 6mm +

xx 13mm Width (from trv image) = 6 ++ 11mm 6+6+4 divided by 3 = 5.3, +30 = 35.3d or 5w Width 15mm MSD 13 = 43d =6w1d

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Human Chorionic Gonadotropin Beta Chorionic Gonadotropin Levels

 Made by trophoblastic cells  MSD Age (weeks) HCG Level  Detectable after implantation  2mm 5.0 1,164  5mm 5.4 1,932  Doubling time every 2-3 days  10mm 6.0 4,478  Correlates well with embryonic and sac size  15mm CRL 6.6 10,379  Level maximizes at about 8 weeks  20mm 7.3 24,060  Max level is about 50,000 -100,000 IU/L  Declines after 10-12 weeks * Filly, in Ultrasonography in and Gynecology, ed Callen, W.B. Saunders, Philadelphia, 1994.

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3 4-5mm Embryonic Timeline

 Week 6: Heartbeat will be detectable during this week. This is the neural tube stage x  Weeks 6-10: Essentially all of the tissues and organs x of the 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.

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5w5d 6w1d 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

3 days development and growth 21 22

6w3d

2mm

Yolk sac and the Early Embryo

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4 Embryonic Period 8w CRL = 18mm 8w3d

Oblique Scanning Plane Fluid?

Fluid?

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Don’t include the yolk sac in the CRL

13mm

7w2d

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Be aware of fetal position

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5 6w1d 7w4d

8w4d 10w3d 31 32

Manipulation of Transducer for CRL After 13 weeks use BPD, HC, AC, and FL

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Skeletal Development 10w3d

8w2d 9w3d

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Indications for a First Trimester Scan Significance of the Yolk Sac

 Vaginal bleeding  Earliest landmark in the early gestational sac

 Size and date discrepancy  Identifies an IUP

 No heart tones  Helps to locate the embryo and heart beat

 Pelvic pain  Should be round and “cystic” 3-6mm

 Accurate dating for future C-section  1 yolk sac per embryo, can help identify monoamnionic twins  History of an anomaly  Should disappear by 12 weeks  Trauma

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7 Week Embryo 7 Week Embryo

Yolk Sac

Amnion

Chorionic Fluid Amniotic Fluid

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Yolk Sac Too big

Yolk Sac 1 cm

1.5 cm

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7 Vaginal Bleeding (1st Trimester)

 Implantation Bleed  Abortion  Subchorionic Hemorrhage  Placental Previa  Ectopic  Blighted Ovum Compressed Yolk Sac

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The future Jen Shepherd Implantation Bleed

 Most common cause of 1st trimester vaginal bleeding  Generally not significant  Sonolucent area between the chorion and uterus (near the internal os)

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Vaginal Bleeding (1st Trimester) Subchorionic Bleeds

 Can be behind the placenta  Implantation Bleed  Can be behind the chorion lavae  Subchorionic Hemorrhage  Can be behind the chorionic plate of the placenta  Abortion  Prognosis depends upon the cause and how much  Placental Previa of the placenta is involved: >1/3 prognosis worsens  Ectopic Pregnancy

 Blighted Ovum

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8 1/4 of placenta is separated from uterus

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8w2d

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 Blighted Ovum: Arrested or absent development of Vaginal Bleeding: 1st Trimester the embryonic pole (trophoblasts develop)

 Implantation Bleed

 Subchorionic Hemorrhage

 Blighted Ovum  Placental Previa

 Ectopic Pregnancy

 Abortion

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9 Growth will fall off No embryo HCG will level off or Yolk Sac Sac may move toward Cx

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Trophoblastic ring may become irregular and thin < 2mm

Video Clip 57 58

Placenta Previa Vaginal Bleeding: 1st Trimester 12w2d

 Implantation Bleed

 Abortion

 Subchorionic Hemorrhage  Placental Previa

 Ectopic Pregnancy

 Blighted Ovum

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10 Vaginal Bleeding: 1st Trimester Glossary of 1st Trimester Terms

 Abortion: Premature expulsion of the gestation  Implantation Bleed from the uterus

 Abortion  Incomplete Abortion: The expulsion of only a  Subchorionic Hemorrhage portion of the gestational products from the uterus

 Placental Previa

 Ectopic Pregnancy

 Blighted Ovum

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Retained Products of Conception

Inevitable Abortion

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Findings for Embryonic Demise Findings for Embryonic Demise Old Criteria  No Sac Growth on Serial Exams  The Findings Below Depend upon Body Habitus and Type of Transducer, Endovag or transabd  A 7 -10 day interval between scans is recommended  No Sac Growth on Serial Exams  Give the embryo a chance  No Cardiac Pulsations in a 5mm Embryo  EV scanning is always best  No Embryo Seen in a Sac 25mm MSD  Abdallah et al US Obstet & Gynecol 2011  No Yolk Sac Seen in a 20mm MSD Sac

 Trophoblastic Ring is not Intact

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11 The Gestational Sac Grows about 1mm/Day 1 Week Should Give a Statistically Significant Increase in MSD Findings for Embryonic Demise Jan 4 Jan 11  Slow Cardiac Pulsations in a 5 (now 7) mm Embryo in an endovaginal ultrasound examination

MSD = 3mm MSD = 10mm 67 68

Reading an M-Mode Findings for Embryonic Demise

 No Cardiac Pulsations in a 9mm Embryo in a transabdominal ultrasound examination

1 second 1 second M-Mode No Heart-beat

Heart rate only 60 bpm Heart rate 160 bpm

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12 Video Clips

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Video Clips Video Clips

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

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13 Findings for Embryonic Demise Findings for Embryonic Demise  No Embryo Seen in a Sac 25mm MSD in an  No Yolk Sac Seen in a 10mm MSD Gestational Sac transabdominal or EV ultrasound examination with endovaginal scanning

 Was 20mm

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Findings for Embryonic Demise New Criteria for Embryonic Demise  No Yolk Sac Seen in a 20mm  No Sac Growth on Serial Exams MSD Gestational Sac with  No Cardiac Pulsations in a 7 mm Embryo* transabdominal scanning  No Cardiac Pulsations in a 9mm Embryo **

 No Embryo Seen in a Sac 25 mm MSD* MSD 25mm  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

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Anembryonic Pregnancy Oligohydramnios Small for Dates S < D

 Normal Pregnancy / Wrong Dates

 Anembryonic Pregnancy (blighted ovum)

 Ectopic Pregnancy Embryonic Demise  Fetal Demise Ectopic Pregnancy  Oligohydramnios

 Intrauterine Growth Retardation (IUGR)

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14 Pseudo-sac Ectopic Pregnancy

 95% occur in the tube  5% are interstitial and are the most dangerous  Cornual and cervical ectopics are increasing Transabdominal scans

 In vitro procedures increase the chance of ectopic pregnancy

 Heterotopic: IUP plus an ectopic

Pseudo-sac 85 Endovaginal scans 86

Ruptured Ectopic

87 Live Ectopic Pregnancy in Right Fallopian Tube 88

Cervical Ectopic Pregnancy Ectopic Pregnancy in Right Cornu

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15 Right & Left Horns of Ectopic? Bicornuate Uterus Uterus?

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Hemorrhagic Corpus Luteum Can Look Like an Ectopic

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Molar Pregnancy

 Large for Dates  Vaginal Bleeding  Very High HCG  May be a live embryo  1 in 1200 in the USA  Risk is 20-40 fold higher if patient had a previous molar pregnancy (1 in 30-60)

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16 Theca Lutein Cysts There may or may not be a sac.

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

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Video Clip Large for Dates

 Normal Pregnancy / Wrong Dates

 Molar Pregnancy

 Gestation with Mass / Masses

 Multiple Gestation

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17 Bicornuate Uterus

IUP Hydatidiform Mole Theca Lutien Cysts

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Early Pregnancy with a Mass Multiple Gestation

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Video Clip Triplets

Bleeds

3 1 2

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

B A  Anencephaly  Conjoined twins E  Acrania  Large omphalocele

C D  Cystic hygroma  Severe gastroschisis

 Hydrops  Thanatophoric dwarf

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Normal Head at 12 Weeks Video Clip Transverse Head at 12 Weeks

Choriod Plexus Frontal

Occipital

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2mm

Acrania at 10w2d Normal Nuchal Translucency 10w6d

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19 Normal Herniation of the Gut Omphalocele into the Base of the Cord at 11w2d 12w4d

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Questions?

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