The 1st trimester ultrasound; What have we learned?
GLYNIS SACKS M.D VANDERBILT CENTER FOR WOMEN’S IMAGING TRS February 2020
I have no conflicts of interest Introduction
Cesarean section predisposes to scar pregnancies as well as placenta accreta spectrum
Not two separate entities but the consequence of a single abnormality.
Left untreated, scar pregnancies may transform into placenta increta or percreta C-section scar pregnancy
Uncommon but increasing in frequency and potentially devastating
Thought to occur when the blastocyst implants on fibrous scar tissue within the wedge-shaped myometrial defect in the anterior lower uterine segment at the site of a prior C-section scar
Fibrosis after multiple C-sections may decrease vascularity which limits healing. Multiple previous C-section deliveries also increase the risk of scar implantation because of the larger scar surface area
Incidence increasing with a resultant increase in placenta accreta, uterine rupture and massive hemorrhage C-section scar pregnancy
Call be classified into different subtypes depending on:
Gestational age at diagnosis
Presence or absence of cardiac activity
Myometrial thickness of lower uterine segment
Appearance of the uterine-bladder interface
Reliable diagnostic criteria for timely diagnosis are necessary given the potential for serious complications. Placenta Accreta Spectrum
May result from defective development of the decidua basalis allowing the trophoblastic tissue to invade the myometrium
Defect of the endometrial-myometrial interface leads to failure of normal decidualization in the area of the scar
Allows abnormally deep placental anchoring villi
Cesarean scar pregnancy is a precursor to PAS
Counselling is challenging
Identify those cases amenable to successful pregnancy outcome
Postnatal treatment Terminology
Placenta Accreta
Vera
Increta
percreta Morbidly Adherent Placenta Placenta Accreta Spectrum Placenta Accreta Spectrum
Significant cause of maternal morbidity & mortality Risk factors Previous C-section Placenta previa IVF-ET Placenta Accreta Spectrum
Courtesy of Phillipe Jeanty Why are we concerned?
Placenta accreta spectrum poses a significant risk to the pregnant patient
Incidence is increasing from 1:2500 – 1:533 pregnancies 40-60% of cases are only diagnosed at the time of delivery 71% of patients require a hysterectomy 25% of patients lose more than 5 liters of blood Mortality rate of cesarean hysterectomy is 10% in patients with a placenta percreta Placenta Accreta Spectrum
Outcomes are optimized when deliveries are performed at Level 3 or 4 maternal care facilities
Before the onset of labor ~34-36 weeks
Cesarean hysterectomy with the placenta left in –situ
Comprehensive multidisciplinary team
Gynecologic oncologist
Interventional radiologist Placenta Accreta Spectrum
Does 1st trimester ultrasound have a role in predicting patients at risk for placenta accreta?
What is the connection with scar pregnancy implantation? 80 No Previa Placenta Previa
70
60
50 Accreta 40
30
20 % Placenta % 10
0 0 1 2 3 4 5 Number of Prior C- Sections 1st trimester findings
Cesarean scar pregnancy Not an ectopic as it is within the uterine cavity Either implants on the scar In the dehiscence (“niche”) at the hysterotomy site C-section scar pregnancy
May present with pelvic pain & bleeding ~ 33% of patients are asymptomatic
Transvaginal ultrasound diagnostic
Spectrum
Severe cases with little or no surrounding myometrium with risk of rupture
Less severe cases evident later with placenta accreta and increased maternal morbidity Scar pregnancy; progression
Implantation of the trophoblast may occur along the surface of the scar Followed by growth towards the uterine cavity Portion of the trophoblast remains anchored Placenta accreta spectrum in the 3rd trimester
Deep implantation in the scar Growth toward the bladder Minimal or absent myometrium Increased risk of hemorrhage & uterine rupture 1st trimester significance
Important to recognize in failed IUP May result in torrential hemorrhage if D&C is performed blindly
Scar implantation Early Diagnosis
Can we identify those patients at risk early in pregnancy Counseling Early Referral 1st trimester findings in Accreta
Implantation on or in the hysterotomy scar (low & anterior) Presence of hypoechoic lacunae within the placenta Thinning of the retroplacental-myometrial zone Irregular or disrupted bladder interface Irregular placental-myometrial interface increased vascularity with “bridging” vessels Placenta Accreta Spectrum
Following scar implantation, varying degrees of placental invasion may be seen with those pregnancies that develop in the endometrial cavity
Signs of PAS include
Focal uterine “bulge”
Obliteration of normal placental-myometrial interface
Vascularized lacunae thought to represent areas of hemorrhage or infarction
Increased flow Early Increta Early Increta
Accreta in the 1st trimester
> 3 lacunae Turbulent flow Location of scar pregnancies
Ilan Timor-Tritsch NYU Scar pregnancy
“empty” uterine cavity with visualization of the endometrial echo
Gestational sac in the anterior lower uterine segment
Thin/absent myometrium between the gestational sac and the bladder wall C-section Scar Pregnancy
Low anterior sac Above the cervix Scar pregnancy
Thin/no myometrium between the placenta & bladder Scar implantation
5 weeks 6 days
Scar implantation
8 weeks 5 days
Delivered at 31 weeks
Placenta previa & accreta. Uterine Position
Anteverted-retroflexed uterus Thin or no myometrium between placenta and bladder
C-section scar pregnancy
Sonography Detection of placenta and/or gestational sac in hysterotomy scar Yolk sac &/or embryo with or without cardiac activity Marked peritrophoblastic color Doppler flow Thin or absent myometrial layer between sac and bladder Closed endocervical canal
Differential diagnosis Cervical ectopic Abortion in progress Normal low implantation Miscarriage “in-progress” Cervical ectopic Cervical ectopic
Scar pregnancy
Low anterior implantation of the gestational sac Center of the sac in the lower half of the uterus Not reliable after 9 weeks Placenta remains in close proximity to the hysterotomy site. Placenta anchored in hysterotomy scar Placenta Increta Scar Pregnancy
Post 1 dose Methtrexate Turbulent flow Bridging vessels C-section scar pregnancy
MRI If ultrasound is equivocal
Even late detection of placenta accreta allows appropriate surgical planning C-section scar ectopic C-section scar pregnancy
Optimal management uncertain uterine rupture or unstable patient = surgery Avoid D & C (profuse bleeding) Methotrexate, KCl or hypertonic glucose Local vs systemic Bilateral uterine artery embolization or intracervical vasopressin ? Scar revision C-scar pregnancy: management
Management options are influenced by
Gestational age at diagnosis
Severity of abnormal placentation
Clinical stability
Desire for future fertility Treatment options
Systemic Methotrexate
Relatively low efficacy if beta hCG is > 5000 mIU
High rates of future pregnancies if successful
Slow regression of trophoblastic tissue Local Methotrexate with/without systemic Methotrexate
If beta hCG > 10,000 mIU Uterine Artery embolization
Requires further intervention in > 80% of cases Hysteroscopy
Direct visualization & vascular coagulation Treatment Options
Minimally invasive treatment of scar & cervical pregnancies using a cervical ripening double balloon catheter
Upper balloon in the uterine cavity serves as an anchor.
Lower balloon at the level of the gestational sac
Foley catheter as an adjuvant therapy to prevent or control bleeding after local Methotrexate or KCl injection
Early expulsion of the balloon Heterotopic Pregnancy
C-section scar ectopic
Normal IUP June 25,2018 July 17,2018 s/p 3 doses Methotrexate
September 6,2018 October 3,2018 Be Aware 31 weeks
Conclusions
Prevalence of Placenta Accreta Spectrum is increasing
Patients can be identified in the 1st trimester
Major risk factors
Placenta previa
Previous C-Section
Imaging findings
Lacunae
Abnormal vascularity
MRI
Ambiguous findings
Posterior placenta Conclusions
Sonographic evaluation
Can detect 50-80% of cases
Includes transabdominal & transvaginal evaluation
Highest resolution transducer possible
Doppler imperative
Abnormal Doppler may be due to different levels of expression of vascular endothelial growth factors and their receptors in the abnormally adherent placentas. Conclusions
Combining ultrasound, Doppler & MRI if necessary allows early recognition of Cesarean scar pregnancies
Allows effective fertility preserving treatment
D&C for unrecognized failed scar pregnancies may lead to significant blood loss
High risk of hysterectomy
local methotrexate better than systemic methotrexate
Offers fertility preservation in asymptomatic patients Conclusions
Not all scar pregnancies result in PAS
All cases of PAS began with implantation involving the scar On the scar In the “niche” (worse outcome)
Early identification of patients at risk is essential
All patients with a history of prior C-sections should be scanned at ~ 7 weeks in future pregnancies