Abnormalities in first trimeter of OBS scan complete lecture

Ultrasound Scan OBS

1. o
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2. OBJECTIVES

* What does abnormal first trimester scan mean? : Predictors
of abnormal early pregnancy
* Sonographic signs of abnormal first trimester scan:
* Miscarriage.
* Ectopic pregnancy.
* Molar pregnancy.
* Some abnormal gynecologic lesions during pregnancy.
* Practical management of abnormal sonographic findings during first trimester.

3. * 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.

4. WHAT IS NORMAL 15T A SCAN

* Intra-uterine pregnancy.
* Single

* Living

* In-dates.

* Normal yolk sac

* NT within normal limits.
* No hematoma.

* Free adnexa (apart from normal CL).

6. CLINICALLY ABNORMAL FIRST A
*Bleeding: d

* 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

7. «Pain:
* Pregnancy specific.
* Pregnancy non-specific.

* Hyperemesis gravidarum:
*Associated masses:

* Genital.
* Extra-genital.

8. I- THREATENED MISCARRIAGE

* Live intrauterine gestation
* Cervix is closed.

* + subchorionic haemorrhage.

9. N

GOOD PROGNOSIS BAD PROGNOSIS

.

* FHR> 90 bpm
* Yolk sac < 7 mm

Fetal bradycardia: <80-90 bpm

Large and calcified yolk sac of > 7

mm
* Small or irregular gestational

} sac: MSD/CRL >5 mm

= Small subchorionic haemorrhage <
1/5 of gestational sac

Small or irregular gestational
sac: MSD/CRL <5 mm

Large subchorionic haemorrhage>
2/3 of gestational sac

* Small mean gestational sac diameter

Small mean gestational sac diameter il

* Normal amnion size. Expanded amnion sign (an
* Normal decidual reaction, abnormally large amniotic cavity)
7 * Absent or poor decidual reaction

10. 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%.

12. i

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.

13. * 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.

14. * 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

16. Meri D”.

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RT OVARY

21. 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).

22. li
IV- PREGNANCY OF UNKNOWN LOCATION (
1 Le"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 maybe either:
* Very early pregnancy, not yet detected with ultrasound
* Complete miscarriage
* Unidentified ectopic pregnancy

23. N

* Sonographic features

* Essentially these patients will present with a "normal" pelvic
0 ultrasound, with no signs of an IUP and normal adnexa.

* Markers

* Serial & -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 mlU/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.

24. N

* TVS:

* Empty uterus:
* BhCG:

* > 1500: action: you should diagnose or wait a maximum of 48 hours
and rescan

* < 1500: action: serial BhCG
* Normal rising: san -> healthy IUP
* Abnormal rising: scan > PUL or EP or unhealthy IUP.

25. 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: (0 >> 4 >> 11)

* 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

26. >

*Findings suspicious but not diagnos
\ of pregnancy failure: action: wait 7-14
a days.

* Single scan:

* CRL: of <7 mm and no heartbeat

* Mean sac diameter (MSD) of 16-24 mm and no embryo
* Serial scan:

* No pulsating embryo 7-13 days after a scan that showed a gestational sac without a yolk
sac

* No pulsating embryo 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)

28. VI. ANEMBRYONIC PREGNANCY

Os 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:

* 211 days after scan showing gestational sac with yolk sac, but
no embryo, or

PNR ee Ce A A

29. >
* Suggestive features
> 2 «Assessment of interval mean sac diameter (MSD) growth
rate: not useful, due to an overlap between viable and
non-viable pregnancies.
* Absent yolk sac when MSD >8 mm on transvaginal
ultrasound (TVS)
* Poor decidual reaction: often <2 mm.
* Irregular gestational sac shape.
* Abnormally low sac position.

30. E ®

VII- PREGNANCY OF UNCERTAIN VIABILITY

| E (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 GS with an embryo with CRL <7
mm with no fetal cardiac activity.

*Gestational sac with MSD <25 mm containing

33. i

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.

34. SAG UTERUS

35. 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

37. i
N

lo) * Definitive diagnosis by ultrasound is often difficult.

IX_1. PARTIAL HYDATIDIFORM MOLE

* 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

38. * 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

40. , X- DEMISE OF A TWIN

ih “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.

41. YANISHING
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