Abnormal first trimester scan

abnormal findings during first trimester scan

1. Abnormal first trimester scan Dr mahmoud abdel-aleem Professor of obstetrics and Gynecology, Assiut university.

2. Acknowledgments

3. 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.

4. 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.

5. 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

6. 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)

7. What is normal 1 st ∆ scan Intra-uterine pregnancy. Single Living In-dates. Normal yolk sac NT within normal limits. No hematoma. Free adnexa (apart from normal CL).

8. 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.

9. 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).

10. 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.

11. 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

12. 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 MSD growth.

13. 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.

14. 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 +/-5 days (95% confidence range).

15. 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.

16. 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

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

18. I- Threatened miscarriage Live intrauterine gestation Cervix is closed. ± subchorionic haemorrhage.

19. 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

20. 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.

21. 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.

22. 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

23. 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).

24. 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

25. 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. 

26. 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 gestational sac with a yolk sac

27. 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 between mean sac diameter and crown-rump length) Large amniotic cavity (expanded amnion sign)

28. Gestational sac

29. 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 ≥ 14 days after a scan showing gestational sac without yolk sac or embryo

30. 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. Abnormally low sac position.

31. 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. Gestational sac with MSD <25 mm containing no embryo

32. 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.

33. 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

34. 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 with intermingling cystic spaces

35. 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

36. 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%.

37. 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.

38. conclusions