abnormal findings during first trimester scan

1. ABNORMAL FIRST TRIMESTER
SCAN
DR MAHMOUD ABDEL-ALEEM
PROFESSOR OF OBSTETRICS AND GYNECOLOGY, ASSIUT UNIVERSITY.

3. ACKNOWLEDGMENTS

4. OBJECTIVES
•What does abnormal first trimester scan mean?
•Sonographic signs of abnormal first trimester
scan: we will discuss 11 items eg miscarriage,
ectopic pregnancy, molar pregnancy.

5. • First trimester is defined as the first 13 weeks of
pregnancy following the last normal menstrual period.
It can be divided into a number of phases, each of
which has typical clinical issues. These phases are:
• Conceptus phase: 3-5 weeks
• Embryonic phase: 6-10 weeks
• Fetal phase: 10-12 weeks
• By ultrasound, the pregnancy progresses from a tiny
gestational sac with no visible embryo, to an ~80 mm
fetus with identifiable features and internal organs.

6. MENSTRUAL AGE EMBRYOLOGIC EVENT
LABORATORY AND TRANSVAGINAL
SONOGRAPHIC DISCRIMINATORY
FINDINGS
Three to four weeks Implantation site Decidual thickening
Four weeks Trophoblast Peritrophoblastic flow on color flow Doppler
Four to five weeks Gestational sac Present when beta subunit of human
chorionic gonadotropin level is greater than
1,500 to 2,000 mIU per mL (1,500 to 2,000
IU per L; varies with sonographer
experience and quality of ultrasonography)
Five to six weeks Yolk sac Present when diameter of gestational sac is
greater than 10 mm
Five to six weeks Embryo Present when diameter of gestational sac is
greater than 18 mm
Five to six weeks Cardiac activity Present when embryonic crown-rump length
is greater than 5 mm

7. AIM OF FIRST ∆ SCAN
• Confirming intrauterine pregnancy (IUP)and number
• Early features supportive of an intrauterine pregnancy
• Double decidual sac sign
• Intra-decidual sign
• Double bleb sign
• Later features: gestational sac then yolk sac then fetal pole.
• Dating of the pregnancy
• Mean sac diameter
• crown rump length (CRL) measurement.
• Assessment of suspected early pregnancy failure
• Assessment of suspected ectopic pregnancy
• Antenatal screening for aneuploidy (nuchal lucency measurement)

8. WHAT IS NORMAL 1ST ∆ SCAN
• Intra-uterine pregnancy.
• Single
• Living
• In-dates.
• Normal yolk sac
• NT within normal limits.
• No hematoma.
• Free adnexa (apart from normal CL).

9. DOUBLE DECIDUAL SAC SIGN (DDSS)
 A useful feature on early pregnancy ultrasound to confirm an early
IUP when the yolk sac or embryo is still not visualized.
It consists of the decidua parietalis (lining the uterine cavity) and
decidua capsularis (lining the gestational sac) and is seen as two
concentric rings surrounding an anechoic gestational sac.
Present in 53%of IUP.
If DDSS is present, it is highly suggestive that the intrauterine fluid
collection is an intrauterine pregnancy.
If DDSS is absent, this does not define a pseudogestational sac.

11. DOUBLE BLEB SIGN
• It is a sonographic feature where there is visualization of a
gestational sac containing a yolk sac and amniotic sac giving
the appearance of 2 small bubbles.
• The embryonic disc is located between the 2 bubbles
• Seen when the CRL is 2 mm (5.5 weeks).

12. GESTATIONAL SAC (GS)
• The first sign of early pregnancy on ultrasound.
• Seen with TVS at 3-5 weeks gestation when the mean sac
diameter (MSD) would approximately measure 2-3 mm in
diameter.
• A true gestational sac can be distinguished from
a pseudogestational sac by noting:
• Its normal eccentric location.
• it is embedded in endometrium, rather than centrally within the uterine
cavity.
• Presence of the double decidual sign (most helpful at 4.0-6.5 weeks).
• Presence of a yolk sac: seen at approximately 5.5 weeks.

13. MEAN SAC DIAMETER (MSD)
• A sonographic measurement of the gestational
sac which is usually first seen at around 3 weeks after
conception (5 weeks after the last menstrual
period), when it measures 2-3 mm.
• MSD = (length + height + width)/3
• Normal MSD (in mm) + 30 = days of pregnancy

14. ROLE OF MSD IN EVALUATION OF
PREGNANCY VIABILITY
TRANSVAGINAL SCAN
• MSD 8 mm = a yolk sac should be
visible, however
• MSD 16-24 mm without an embryo is
suspicious for pregnancy failure, but
not definitive.
• MSD >25mm with absent fetal pole
indicates pregnancy failure (missed
miscarriage)
TRANS-ABDOMINAL SCAN
• MSD measures 20 mm= a yolk
sac should be visible
• MSD measures ≥25 mm = fetal
pole should be visible
MSD should be at least 5 mm greater than the CRL.
The MSD increases by about 1 mm per day.
Lack of a yolk sac is not a definite indication of pregnancy failure
The diagnosis of pregnancy failure should not be made on the basis of

15. YOLK SAC
• It appears within the gestational sac at five to six menstrual
weeks.
• This is the first sonographic finding that positively confirms
intrauterine pregnancy.

16. CROWN RUMP LENGTH (CRL)
• The length of the embryo or fetus from the top of its head to bottom
of trunk.
• It is the most accurate estimation of gestational age in early
pregnancy, because there is little biological variability at that time.
• It is measured as the largest dimension of embryo, excluding the
yolk sac and extremities. It is used as a primary measure of
gestational age between 6-13 weeks.
• The earlier in pregnancy a scan is performed, the more accurate the
age assignment from crown rump length.
• If the original CRL measurement was adequate, the measurement is
considered the baseline for all subsequent age measurements.
• Overall, the accuracy of sonographic dating in the first trimester is

17. • Cardiac activity should be present in an embryo with a CRL ≥7
mm . If it not detected at this size on transvaginal scanning
performed by an experienced operator, it is an indicator
of failed early pregnancy (missed miscarriage).
• If MSD (mean sac diameter) is (< 5 mm) greater than crown
rump length (i.e. MSD - CRL = <5 mm) are prone to first
trimester miscarriage, despite a normal heart rate.
• Chromosomal anomalies, particularly trisomy
18 and triploidy are markedly associated with growth
restriction, i.e. decreased crown rump length.

19. CLINICALLY ABNORMAL FIRST ∆
•Bleeding:
• Originating from uterus, tubes, amniotic sac with its contents or placenta:
• Ectopic pregnancy
• Miscarriage/ Miscarriage with infection
• Molar pregnancy
• Subchorionic hemorrhage
• Idiopathic bleeding in a viable pregnancy
• Originating from cervix or vagina:
• Infection (Chlamydia, etc.)
• Trauma (e.g. after intercourse, medical treatment)
• Malignancies, especially cervix cancer
• Cervical abnormalities (e.g. excessive friability or polyps)
• Originating from anus, bladder or vulva:
• Hemorrhoids.
• Lacerations of skin due to trauma, malignancy (rare) or infection
• UTI, schistosomiasis

20. •Pain:
• Pregnancy specific.
• Pregnancy non-specific.
• Hyperemesis gravidarum:
•Associated masses:
• Genital.
• Extra-genital.

21. I- THREATENED MISCARRIAGE
• Live intrauterine gestation
• Cervix is closed.
• ± subchorionic haemorrhage.

22. GOOD PROGNOSIS
• FHR> 90 bpm
• Yolk sac < 7 mm
• Small or irregular gestational
sac: MSD/CRL >5 mm
• Small subchorionic haemorrhage <
1/5 of gestational sac
• Small mean gestational sac diameter
• Normal amnion size.
• Normal decidual reaction.
BAD PROGNOSIS
• Fetal bradycardia: <80-90 bpm
• Large and calcified yolk sac of > 7
mm
• Small or irregular gestational
sac: MSD/CRL <5 mm
• Large subchorionic haemorrhage>
2/3 of gestational sac
• Small mean gestational sac diameter
• Expanded amnion sign (an
abnormally large amniotic cavity)
• Absent or poor decidual reaction

23. II- ECTOPIC PREGNANCY
• The ultrasound exam should be performed:
• TAS: provides a wider overview of the abdomen
• TVS: is important for diagnostic sensitivity.
• Positive sonographic findings include:
• Uterus.
• Empty uterine cavity or no evidence of intrauterine pregnancy
pseudogestational sac or decidual cyst: may be seen in 10-
20% of ectopic pregnancies
• Thick echogenic endometrium.

24. • Tube and ovary
• Simple adnexal cyst: 10% chance of an ectopic
• Complex extra-adnexal cyst/mass: 95% chance of a tubal
ectopic (if no IUP)
• an intra-adnexal cyst/mass is more likely to be a corpus luteum
• Tubal ring sign
• 95% chance of a tubal ectopic if seen
• described in 49% of ectopic and in 68% of unruptured ectopic
• Ring of fire sign: can be seen on colour Doppler in a tubal
ectopic, but can also be seen in a corpus luteum. Absence of
colour Doppler flow does not exclude an ectopic.
• Live extrauterine pregnancy (i.e. extra-uterine fetal cardiac
activity): 100% specific, but only seen in a minority of cases.

25. •Peritoneal cavity
• Free pelvic fluid or hemoperitoneum in the pouch of
Douglas
• The presence of free intraperitoneal fluid in the context
of a positive beta HCG and empty uterus is
• ~70% specific for an ectopic pregnancy.
• ~63% sensitive for ectopic pregnancy

32. III- HETEROTOPIC PREGNANCY
• IVF patients: there is a possibility of a coexisting ectopic
pregnancy in ~1:500.
• Non- IVF patients, the risk of heterotopic pregnancy is
minuscule (1:30,000).

33. IV- PREGNANCY OF UNKNOWN LOCATION
•”PUL” is assigned when neither an (IUP) or an (EP) is
identified on TVS + +ve pregnancy test.
•Clinical presentation
• Pelvic pain, vaginal bleeding
• Positive pregnancy test
•A pregnancy of unknown location basically reflects three
possibilities:
• Very early pregnancy, not yet detected with ultrasound
• Complete miscarriage
• Unidentified ectopic pregnancy

34. • Radiographic features
• Essentially these patients will present with a "normal" pelvic
ultrasound, with no signs of an IUP and normal adnexa.
• Markers
• Serial ß -hCG: has an adjunct role in the diagnosis of ectopic pregnancy, and is
useful in the follow-up of clinically stable patients. Single reading > 1500-
2000 mIU/mL should be conclusive
• Serum progesterone <5 ng/mL is a good indication of nonviability.
• Larger values cannot exclude an ectopic pregnancy.
• Treatment and prognosis
• In hemodynamically stable patients, serial quantitative beta-hCG
levels and a repeat ultrasound examination in a short interval are
the management of choice.

35. V. FAILED EARLY PREGNANCY
• Death of the embryo and therefore, miscarriage.
• Diagnostic Ultrasound Findings of pregnancy failure: action:
terminate
• Single scan:
• CRL of ≥7 mm and no heartbeat on a transvaginal scan
• MSD of ≥25 mm and no embryo on a transvaginal scan
• Serial scan:
• Absence of embryo with heartbeat ≥15 days after a scan that showed a
gestational sac without a yolk sac
• Absence of embryo with heartbeat ≥11 days after a scan that showed a

36. •Findings suspicious but not diagnostic
of pregnancy failure: action: wait 7-14
days.
• Single scan:
• CRL: of <7 mm and no heartbeat
• Mean sac diameter (MSD) of 16-24 mm and no embryo
• Serial scan:
• Absence of embryo with heartbeat 7-13 days after a scan that showed a gestational sac
without a yolk sac
• Absence of embryo with heartbeat 7-10 days after a scan that showed a gestational sac
with a yolk sac
• Absence of embryo ≥ 6 weeks after last menstrual period amnion seen adjacent to
yolk sac, with no visible embryo (empty amnion sign) enlarged yolk sac (>7 mm)
• Small gestational sac in relation to the size of the embryo (<5 mm difference

37. GESTATIONAL SAC

38. VI. ANEMBRYONIC PREGNANCY
• This is a subtype of failed intrauterine pregnancy.
• TAS and TVS show a uterus with an intrauterine gestational sac.
• Single scan:
• MSD is at least 25 mm on the transvaginal scan with no embryo
or yolk sac.
• The cervix is long and closed. Both ovaries are normal with no
adnexal mass or free fluid.
• Serial scan:
• ≥11 days after scan showing gestational sac with yolk sac, but
no embryo, or

39. •Suggestive features
• Assessment of interval mean sac diameter (MSD) growth
has been shown to be insufficiently accurate in the
diagnosis of anembryonic pregnancy, due to an overlap
of gestational sac growth rates of viable and non-viable
pregnancies.
• Absent yolk sac when MSD >8 mm on transvaginal
ultrasound (TVUS)
• Poor decidual reaction: often <2 mm.
• Irregular gestational sac shape.

40. VII- PREGNANCY OF UNCERTAIN VIABILITY
(PUV)
•An intrauterine pregnancy with no enough
criteria (usually on ultrasound grounds) to
confidently categorize an intrauterine
pregnancy as either viable or a failed
pregnancy.
•Intrauterine gestational sac containin
an embryo with CRL <7 mm with no fetal
cardiac activity.

42. TVS
Embryo +ve
≥ 7mm
-ve pulsation
????
< 7mm
-ve pulsations
Rescan 7 days
No embryo
MSD <12 mm
Rescan 14
days
MSD 12-25
mm
Rescan 7 days

43. VIII. INEVITABLE MISCARRIAGE
•Clinically easy to diagnose
• Cervix opened
• Massive bleeding.
•Sonographic signs:
• No cardiac pulsations.
• Opened cervix.
• Displaced intrauterine contents to lower uterine
segment.

45. IX. MOLAR PREGNANCY
• Enlarged uterus
• An intrauterine mass with cystic spaces without any
associated fetal parts
• the multiple cystic structures classically give a "snow storm" or
"bunch of grapes" type appearance.
• Bilateral theca lutein cysts may also be seen on ultrasound
• Color Doppler interrogation may show high velocity with a
low impedance flow

47. IX_1. PARTIAL HYDATIDIFORM MOLE
• Definitive diagnosis by ultrasound is often difficult.
• Described sonographic features include
• Greatly enlarged placenta relative to the size of the uterine
cavity.
• Cystic spaces within the placenta ("molar placenta"), which may
not always be present
• An amniotic cavity (gestational sac), either empty or
containing amorphous small fetal echoes which may be
surrounded by a relatively thick rim of placental echoes

48. • Presence of a well-formed but growth-retarded fetus,
either dead or alive with hydropic degeneration of
fetal parts being frequently present
• Colour Doppler interrogation may show high velocity
and low impedance flow

50. X SUBCHORIONIC HEMATOMA
• Crescentic collection with elevation of the chorionic membrane
• Echotexture is variable:
• Acute: hyperechoic and may be difficult to differentiate from the adjacent chorion
• Subacute-chronic: decreasing echogenicity with time
• There is an extension of the haematoma towards the margin of
the placenta.
• Quantification
• Small: In early pregnancy, if <20% of the size of the sac.
• Large: if >50-66%.

52. XI- DEMISE OF A TWIN
•A complication that can occur in a twin pregnancy.
May be due to many factors.
•May lead to either:
• Vanishing twin syndrome: only one fetus may be identified
on ultrasound of a previously documented twin
pregnancy, and this may be due to resorption or
miscarriage of the demised twin.
• Fetus papyraceus: Once the twin dies, most of the dead
twin tends to be absorbed leaving behind a small flattened
remnant.

54. CONCLUSIONS