antepartum hemorrhage Flashcards
what are the 3 main causes of first trimester bleeding
ectopic
SA
normal pregnancies
what are the major causes of antepartum hemorrhage
placenta previa (20%)
placental abruption (30%)
define placental previa
abnormal implantation of the placenta over the internal cervical os
define complete previa
placenta completely covers the internal os
define partial previa
occurs when the placenta covers a portion of the internal os
define marginal previa
edge of placenta reaches margin of the os
define low lying placenta
implanted in the lower uterine segment in close proximity but not extending to the internal os
define vasa previa
fetal vessel lying over the cervix
define placental migration
with the progression of pregnancy, more than 90% of low lying placentas will appear to move away from the cervix and out of the lower uterine segment
the placenta does not actually move itself, but instead the lower uterine segment stretches and elongates
also the placenta may grow preferentially towards a better vascularized fundus (trophotropism) whereas the placenta overlying the less well vascularized lower uterine segment atrophies
define succenturiate lobe
is cases where atrophy of the placenta in the lower uterine segment is incomplete and leaves a placental lobe discrete from the rest of the placenta
why do placenta previas bleed
results from small disruptions in the placental attachment during normal development and thinning of the lower uterine segment during the third trimester
bleeding may stimulate further uterine contractions which in turn stimulates further placental separation and bleeding
initial bleeds are rarely a problem–> however in labour as the cervix dilates and effaces, there is usually placental separation and unavoidable bleeding –> profuse hemorrhage and shock can occur
what is the rate of maternal mortality due to placenta previa in the US
0.03%–> 10x higher than general pop
list fetal complications associated with placenta previa
preterm delivery and its complications
preterm premature rupture of membranes
intrauterine growth restriction
malpresentation
vasa previa
congenital abnormalities
define placenta accreta
superficial attachment of the placenta to the uterine myometrium
may complicate placenta previa
define placenta increta
invades the myometrium
define placenta percreta
placenta invades the myometrium to the uterine serosa
this may lead to invasions of other organs like the bladder or rectum
why do we care about placenta accreta
causes an inabillity of the placenta to properly separate from the uterine wall after the delivery of the fetus
can result in profuse hemorrhage and shock with substantial maternal morbidity and mortality (need for hysterectomy, surgical injury to ureters, bladder, other viscera, adults respiratory distress syndrome, renal failure, coagulopathy, death)
what is the average blood loss at delivery in women with placenta accreta
3000-5000 mL
what % of women with both placenta previa and accreta require a hysterectomy at the time of delivery
“peripartum hysterectomy”
2/3 require this if have both conditions
list placental causes of antepartum bleeding
placenta previa
placental abruption
vasa previa
list maternal causes of antepartum bleeding
uterine rupture
list fetal causes of antepartum bleeding
fetal vessel rupture
list cervical causes of antepartum bleeding
severe cervicitis
polyps
cervical dysplasia/cancer
list vaginal/vulvar causes of antepartum bleeding
lacerations
varices
cancer
list other causes of antepartum bleeding
hemorrhoids
congential bleeding disorder
abdo or pelvic trauma
hematuria
what % of women with previous C/S get placenta previa
1-4%
what % of women with placenta previa also have placenta accreta
5%—> risk of placenta accreta is increased in women with placenta previa in the setting of prior C/S–> gtes much higher the more C/S the woman has had
why do you get abnormalities in placentation
result of events that prevent normal migration of the placenta during normal progressive development of the lower uterine segment during pregnancy
previous placental implantations and prior uterine scars are thought to contribute (i.e previous myomectomies, uterine anomalies, smoking, previous placenta previa)
how do women with placenta previa usually present
sudden and profuse painless vaginal bleeding
the first/”sentinel” bleedin usually occurs after 28 weeks of gestation
during this time, the lower uterine segment develops and thins, disrupting the placental attachment and resulting in bleeding
how does placenta accreta/incrata usually present
usualyl asymptomatic
on rare occasions, patient with percreta into the bladder or rectum may present with a hematuria or rectal bleeding
how do you examine a woman with placenta previa
vaginal examination is contraindicated as the digital exam can cause further separation of the placenta and trigger catastrophic hemorrhage
if it is undiagnosed prior to exam, and an exam is performed, cervical exam may reveal soft, spongy tissue just inside the cervix
define circumvallate placenta
occurs when the membranes double back over the edge of the placenta, forming a dense ring around the periphery of the placenta–> often considered a variant of placental abruption–> major cause of second trimester hemorrhage
define velamentous placenta
blood vessels insert between the amnion and chorion, away from the margin of the placenta, leaving the vessels largely unprotected and vulnerable to compression or injury
define succenturiate placenta
extra lobe of the placenta that is implanted at some distance away from the rest of the placenta–> fetal vessels may course between the two lobes, possibly over the cervix, leaving these vessels unprotected and at risk for rupture
how do you diagnose placenta previa
U/S–> sensitivity over 95%
follow up U/S in third trimester if dx made in second trimester to determine if has resolved
TRANSVAGINAL U/S is better (transabdominal causes more false positives)
how do you diagnose placenta accreta
U/S or MRI
in which women should you suspect placenta accreta
women who have both placenta previa and a hx of C/S or other uterine surgery
how is placenta previa managed
strict pelvic rest (no intercourse and no excessive activity) and modified bed rest
some clinicians wait until sentinel bleed has happened before instructing strict pelvic rest
some clinicians hospitalize patients after sentinel bleed
what are indications for immediate C/S in setting of placenta previa
unstoppable labour
fetal distress
life threatening hemorrhage
regardless of gestational age
patients with complete or partial previa require C/S
can patients with low lying placenta or marginal placenta previa (more than 2 cm from internal os) delivery vaginally
yes as long as there is no evidence of fetal distress or excessive hemorrhage
what % of women with placenta previa require delivery before week 36 due to recurring bleed episodes
70%
of those that make it to 36 weeks, advise C/S between 36-37 weeks depending on fetal lung maturity
describe a course of action plan in the case of a woman with vaginal bleeding and suspected placenta previa and/or placenta accreta
- stabilize the patient–> every patient with vag bleeding and known or suspected previa should be hospitalized
- place on continuous fetal monitoring
- have IV access established –> if large bleed, two large bore IV catheters
- lab evaluation–> hematocrit, group and screen, PTT, d dimer, fibrinogen
- if Rh -, should do KB test to determine extent of any fetomaternal transfusion –> rhogam if necessary
- if not yet a catastrophic hemorrhage, can do expectant management–> hospitalization, bed rest, hematocrit monitoring, consideration of limiting oral intake–> 1 or 2 units of typed/matched blood should be made available
- transfuse to maintain a hematocrit of 25% or greater
- if woman is between 24-34 weeks when admitted for bleed, give steroids to promote fetal lung maturity
- detailed U/S to exclude accreta
- if before 32 weeks–> manage moderate to severe bleed aggressively with transfusions, rather than moving towards delivery–> cautious use of tocolytics in women with previa who appear to be having contractions can help prolong pregnancy up to 34 weeks
define placental abruption
premature separation of the normally implanted placenta from the uterine wall, resulting in hemorrhage between the uterine wall and the placenta
when do 50% if placental abruptions occur
before labour and after 30 weeks
what % of placental abruptions occur during labour
15%
what % of placental abruptions are found only on placental inspection after delivery
30%
what are the risks associated with placental abruption
premature delivery
uterine tetany
DIC
hypovolemic shock
what is the primary cause of placental abruption and what are associated predisposing and precipitating factors
primary cause unknown –could be due to abnormal placental vasculature, thrombosis, reduced placental perfusion
what are associated predisposing and precipitating factors for placenta abruption
predisposing–
HTN previous abruption advanced maternal age multiparity uterine distension multiple pregnancy polyhydramnios vascular deficiency DM collagen vascular disease cocaine use meth use cigarette smoking alcohol use circumvallate placenta short umbilical cord
precipitating factors–
trauma external/internal version MVA abdo trauma sudden uterine volume loss delivery of first twin rupture of membranes with polyhydramnios PPROM
describe the process of placental abruption
at initial point of separation, non clotted blood courses from the injury site–> enlarging collection of blood may cause further separation from the placenta
in what % if apruptions is bleeding confined within the uterine cavity
20%–> concealed hemorrhage
why can concealed hemorrhages actually cause greater fetal demise
because form retroplacental clots that are asymtomatic to the mom but can cause fetal demise
what is the cause of death in women with placental abruption
hemorrhage
cardiac failure
renal failure
what is the rate of fetal mortality in placental abruption
35% of all clinically relevant antepartum placental abruptions (can be as high as 50-80% if severe)
cause of fetal demise is usually hypoxia from decreased placental surface area and maternal hemorrhage
what % of third trimester bleeding is due to placental abruption
30%
what % of perinatal mortality is due to placental abruption
15%
why is there such high mortality associated with abruption
due to strong association with preterm birth –> more than 50% of excess perinatal deaths in pregnancies with abruption are accounted for by premature delivery
what is the most common factor associated with increased incidence of abruption
HTN (whether due to chronic, preeclampsia, cocaine or meth)
in cases that are severe enough to cause fetal death, 50% are due to HTN (25% chronic HTN and 25% preeclampsia)
what is the further risk of abruption after one abruption
10%
25% risk after 2 prior
what is the classic presentation of placental abruption
third trimester vaginal bleeding associated with severe abdo pain and/or frequent, strong contraction
30% of abruptions are small with few or no symptoms and are only ID-ed after birth
classically taught that painless uterine bleeding is more likely previa and painful bleeding is more likely abruption (however labour accompanying previa may look like abruption)
placental abruption on exam
vaginal bleeding with firm, tender uterus
on tocometer, small, fequent contractions are usually seen along with tetanic contractions
non reassuring NSTs are often seen secondary to hypoxia
what is the classic sign of abruption seen at C/S delivery
Couvelaire uterus–> life threatening condition and occurs when there is enough blood from the abruption that markedly infiltrates into the myometrium to reach the serosa, especially at the cornua, that is gives the myometrium a bluish/purple tone that can be seen on the surface of the uterus
how is apruption diagnosed
mostly clinical
only 2-25% of abruptions are dx through U/S (retroplacental clot)
however, U/S is often done when presenting with abruption to tule out previa with vaginal bleeding
negative findings on U/S CANNOT exclude placental abruption and dx should be confirmed with inspection of placenta at delivery
presence of retroplacental clot with overlying placental destruction confirms the diagnosis
what lab test may indicate a severe abruption
a consumptive coagulopathy (low fibrinogen, high d dimer) due to activation of intravascular coagulation with varying degrees of defibrination
do you have to deliver right away in placental abruption
in some cases due to risk of rapid deterioration but most are small and non catastrophic and thus do not need immediate delivery
describe an action plan for management of a patient presenting with abruption
- if abruption is known or suspected, hospitalize patient and place on continuous fetal monitoring with IV access
- lab eval should include CBC, group and screen, PTT, fibrinogen, d dimer
- rho gam for Rh - women
- notify anesthesia in case C/S is needed urgently
- start infusion of ringers lactate and prepare cross matched blood in case of hemorrhage (help prevent hypovolemia and DIC due to consumptive coagulopathy)
- in preterm pregnancies, can give betamethasone to promote fetal lung maturity; can possibly use tocolytics to prolong pregnancy to week 34 if otherwise stable
- if bleeding is life threatening or fetal testing is non reassuring, should deliver baby regardless of GA or steroid admin status –> vaginal delivery is preferred as long as bleeding is controlled and there are no signs of fetal distress
when do most complete uterine ruptures occur
during the course of labour–> more than 90% of all uterine ruptures are associated with a prior uterine scar either from C/S or other uterine surgery
other than prior uterine scar, what can cause a uterine rupture
abdominal trauma–> MVA, version procedures
associated with labour and delivery–> improper oxytocin use or excessive fundal pressure
spontaneous–> placenta percreta, muliple gestation, grand multiparity, invasive mole, choriocarcinoma
what are the primary maternal complications from a uterine rupture
hemorrhage and hypovolemic shock
what is the overall maternal mortality for uterine rupture
less than 1%
but if rupture occurs in antepartum patient at home, it is higher
what is the risk of uterine rupture in women with low transverse C/S scars? vertical scars?
transverse–0.5-0.1%
vertical–6-12%
list risk factors for uterine rupture
prior uterine surgery/scar
injudicious use of oxytocin
grand multiparity
marked uterine distension
abnormal fetal lie
large fetus
external version
trauma
how does uterine rupture present
highly variable
typically characterized by sudden onset of intense abdominal pain
bleeding may not be present, or may vary from spotting to lots of bleeding
can also have non reassuring NST, abnormal abdo contour, cessation of uterine contractions, disappearance of fetal heart tones, regression of the presenting part
how do you treat uterine rupture
immediate laparotomy and delivery of the fetus
if feasible, rupture site should be repaired and hemostasis obtained–> in cases of large rupture, may need hysterectomy
patients discouraged to attempt further pregnancies due to risk of rupture –> trial of labour should be avoided if they do have another pregnancy
what is the most common reason for fetal vessel rupture?
most due to velamentous cord insertion –> blood vessels insert between amnion and chorion away from placenta instead of directly into chorionic plate
may also occur with a succenturiate lobe of the placenta
what is the pathogenesis behind fetal vessel rupture due to velamentous cord insertion?
because vessels course unprotected through the membranes before inserting onto the placental margin, they are vulnerable to rupture, shearing or laceration
also may cross over the internal os (vasa previa) making them vulnerable to compression by the presenting fetal part or may be torn during the rupture of membranes
what is the perinatal mortality associated with vasa previa
40-60%
increases if membranes are also ruptured
list risk factors for rupture of fetal vessels
abnormal palcentation leading to succenturiate lobe
multiple gestation that increases risk of velamentous insertion
how does vasa previa present
if known–> fetal vessels are palpated and recognized through the dilated cervix
most commonly–> presentation of a fetal vessel rupture is vaginal bleeding associated with sinusoidal variation of the FHR indicative of fetal anemia
whenever bleeding accompanies rupture of membranes in labour, especially is there are associated decels/brady/sinusoidal heart tracing, OB should have high index of suspicion for ruptured vasa previa
what fetal heart tracing is associated with fetal vessel rupture/fetal anemia
sinusoidal
what test can be done at the time of vaginal bleeding to test for vasa previa
Apt test
diluting the blood with water, collecting the supernatant and combining it with 1% NaOH–> if mixture is pink, indicates fetal blood//if yellow-brown it is maternal blood
how do you manage vasa previa/rupture of fetal vessels
high risk of fetal exsanguination and death –> need emergent cesaerean
immediate transfusions may be lifesaving
how do non obstetric causes of antepartum hemorrhage usually present
spotting rather than frank bleeding
no uterine contractions or abdo pain
dx usually by speculum exam
pap tests, cultures or colposcopy as indicated
