12. OB Flashcards
Menstrual Age:
Embryologic Age + 14 days
Embryo:
0-10 weeks (menstrual age)
Fetus:
> 10 weeks (Menstrual age)
Bleeding with closed cervix
Threatened abortion
Cervical dilation and/or placental and/or fetal tissue hanging out
Inevitable abortion
Residual products in the uterus
Incomplete abortion
All products out
Complete abortion
Fetus is dead, but still in the uterus.
Missed abortion
This is the early gestational sac.
Intradecidual sign
Intradecidual sign
You want to see the thin echogenic line o f the uterine cavity pass by (not stop at) the sac to avoid calling a little bit o f fluid in the canal a sac
You can see the early gestational sac around =
4.5 weeks
Double Decidual Sac sign
This is another positive sign of early pregnancy.
This is the first structure visible within the GS.
Yolk Sac
You should always see the Yolk sac when the GS measures =
8 mm
Yolk Sac
Should be oval or round, fluid filled, and smaller than 6 mm.
Where is the yolk sac located?
Chorionic Cavity and hooked up to the umbilicus by the vitelline duct
Normal Appearance of the Yolk Sac
Should NOT be:
Too big (> 6mm)
Too small (< 3 mm)
Solid
Calcified
The membranes of the amniotic sac and chorionic space
typically remain separated by a thin layer of fluid around
14-16 weeks at which point fusion is normal.
Amniotic Band Syndrome
If the amnion gets disrupted before 10 weeks = fetus might cross into the chorionic cavity = get tangled up in the fibrous bands
Double Bleb Sign
“Two fluid filled sacs (Yolk and Amniotic) with the flat embryo in the middle
This is the earliest visualization of the embryo
This is typically used to estimate gestational age, and is more accurate than menstrual history.
Crown Rump Length
Embryo is normally visible at =
6 weeks
A gestational sac without an embryo. When you see this, the choices are:
a. Very Early Pregnancy
b. Non-viable Pregnancy
You should see yolk sac on TVS at ___mm.
8 mm
Large sac (>8-10mm) + Distorted contour + NO yolk sac =
Non-VIable pregnancy
Pseudogestational Sac
“blood in the uterine cavity with surrounding bright decidual endometrium (charged up from the pregnancy hormones)”
small subchorionic hemorrhage that occurs at the attachment o f the chorion to the endometrium.
Implatation Bleeding
Fetal demise in subchorionic hemorhage is strongly associated with?
% of placental detachment
Crown-rump length of >7 mm and no heartbeat
Pregnancy Failure
Mean sac diameter o f >25 mm and no embryo
Pregnancy Failure
No embryo with heartbeat > 2 wks after a scan that showed a Gestational saca withouth yolk sac
Pregnancy Failure
No embryo with heartbeat >11 days after a scan that showed a gestational sac with a yolk sac
Pregnancy Failure
No embryo >6 wk after last menstrual period
Suspicious for Pregnancy Failure
Mean sac diameter of 16-24 mm and no embryo
Suspicious for Pregnancy Failure
No embryo with heartbeat 13 days after a scan that showed a gestational sac without a yolk sac
Suspicious for Pregnancy Failure
No embryo with heartbeat 10 days after a scan that showed a gestational sac with a yolk sac
Suspicious for Pregnancy Failure
This is the vocabulary used when neither a normal lUP or ectopic pregnancy is identified in the setting of a positive b-hCG.
Pregnancy of Unknown Location
Typically this just means it is a very very early pregnancy, but you can’t say that with certainty.
Pregnancy of Unknown Location
3 possibilities in the case of Pregnancy of Unknown Location
- Normal early pregnancy
- Occult Ectopic
- Complete Miscarriage
Pregnancy of Unknown Location management:
Follow up (Serial b-hCG) and repeat US
The following increase the risk of ectopic pregnancy:
Being a free spirit (Hx of FID)
Tubal Surgery
Endometriosis
Ovulation Induction
Previous Ectopic
Use of an lUD.
The majority of ectopic pregnancies (nearly 95%) occur in
Fallopian Tube (AMPULLA)
2% are interstitial = portion of the tube which passes through the uterine wall
Interstitial ectopic implantation risk
Rupture = hemorrhage
Always start down the ectopic pathway with =
(+) BhCG - 1500-2000 mIU/L - you should see a gestational sac
BhCG at around 5000 mIU/L, you should see =
A yolk sac
General rule about BhCG in ectopic pregnancy
Normal doubling time = ectopic less likely
Tubal Ring Sign - 95% specific
“An echogenic ring, which surrounds an un-ruptured ectopic
pregnancy”
This is an excellent sign of ectopic pregnancy
Live Pregnancy / Yolk Sac outside the uterus =
Slamt dunk! ==== ECTOPIC!
Nothing in the uterus + anything on the adnexa (other than corpus luteum) =
75%-85% for ectopic
if + moderate volume of free fluid = 87% positive
Nothing in the uterus + moderate free fluid =
70% PPV
More risk if the fluid is echogenic
Where is BPD measured?
Recorded at the level of the thalamus from the outeiinost edge of the near skull to the inner table of the far skull
Abdominal Circumference is recorded at =
the junction o f the umbilical vein and left portal vein
Femur Length
Longest dimension of the femoral shaft
NOT included = epiphysis
Age in the first trimester is made from
CRL
Second and third trimester estimates for age are typically done using
BPD
HC
AC
FL
Gestation Age accuracy
1st =
2nd =
3rd =
1st = CRL 0.5 weeks
2nd = 1.2 weeks (between 12-18)
3rd = 3.1 weeks (between 36 and 42)
Readings Suggestive of iUGR:
Estimated Fetal Weights Below 10th percentile
Femur Length / Abdominal Circumference Ratio (F /AC) > 23.5
Umbilical Artery Systolic / Diastolic Ratio > 4.0
Most common cause for developing oligohydramnios during the 3rd trimester
= Fetal Growth Restriction associated with Placental Insufficiency.
IUGR + 3rd trimester = Normal head + small body + Mom with pre-eclampsia =
Asymmetric IUGR
IUGR + throughout pregnancy = small overall (head not spared + poor prognosis =
Symmetric IUGR
Causesof Symmetric IUGR
TORCH
Fetal alcohol syndrome
Drug abus
Chromososmal abnormalities
Anemia
Where is MCA doppler done?
Proximal 1/3 of the vessel
Normal fetal MCA
should be a high resistance waveform with continuous forward flow of diastole (the space between the waveform peaks).
Abdnormal fetal MCA
When the fetal brain experiences hypoxia there is a reflex response to protect the brain. This “brain-sparing reflex” will manifest early on as an increase in diastolic flow (less resistance).
This is a ratio of the pulsatility in the MCA and Umbilical Artery that is used to evaluate the brain sparing reflex and predict outcomes.
Cerebroplacental Ratio
Cerebroplacental Ratio: >1:1 is normal
This thing was developed to look for acute and chronic hypoxia.
Biophysical profile
Components of Biophysical Profile
- Amniotic fluid
- Fetal movement = 3 movements
- Fetal tone = 1 ext from flex
- Fetal breathing = 1 episode lasting 30 sec
- Non-stress test = 2 or more FHR accelerations at least 15 bpm for 30 sec or longer
What component of Biophysical Profile is used to assess chronic hypoxia
Amniotic fluid
Macrosomia causes
Maternal DM
Complications of Macrosomia during delivery
Brachial plexus injury
Neonatal hypoglycemia
Meconium aspiration
Injury to the upper trunk o f the brachial plexus (C5-C6), most commonly seen in shoulder dystocia (which kids with macrosomia are at higher risk for).
Erb’s Palcy
Erb’s Palsy
Aplastic or hypoplastic humeral head/glenoid in a kid
Early on, the fluid in the amnion and chorionic spaces is the result of
Filtrate from the membranes
The amniotic is made by the fetus at week?
after 16 weeks
The balance o f too much (polyhydramnios) and too little (oligohydramnios) is maintained by
swallowing of the urine and renal function
if you have too little amniotic fluid you should think
kidneys aren’t working
If you have too much amniotic fluid you should think
swallow or other GI problems
the most common cause of polyhydramios
Maternal DM
Made by measuring the vertical height of the deepest fluid pocket in each quadrant of the uterus, then summing the 4 measurements.
Amniotic Fluid Index.
Normal AFI
5-20 cm
Polyhydramnios is defined as
AFI > 20 cm, or single fluid pocket > 8 cm
Oligohydramnios is a frequent finding in
IUGR related to placental insufficiency
There should be less than __ mm of separation of the choroid plexus from the medial wall of the lateral ventricle.
If more = think of
< 3 mm
If more = ventriculomegaly
Normal Cisterna magna measurement
Too small =
Too large =
2 - 11 mm
Too small = Chiari II
Too large = Dandy Walker
the lung of the fetus should be similar in appearnce to the
LIVER - homogeneously echogenic
Calcified papillary muscle is associated with increased risk of?
Downs
“Echogenic foci in the ventricle”
Bowel should be less than ___ mm in diameter
Bowel should be less than 6mm in diameter.
Bowel can be moderately echogenic in the 2nd and 3rd trimester but should never be more than
Bone
Adrenals are how many times largert than their relative adult size?
20x
There are two main ways to show a two vessel cord
The first one is a single vessel running lateral to the bladder down by the cord insertion
The second is to show the cord in cross section with two vessels.
Normal Cystic Rhombencephalon (6-8 weeks)
cystic structure in the posterior fossa around 6-8 weeks
D on’t call it a Dandy-Walker malformation, for sure that will be a distractor.
Welcome to your nightmare, bitch! j
Physiologic Midgut Herniation
The midgut normally herniates into the umbilical cord around 9-11 weeks
Don’t call it an omphalocele, for sure that will be a distractor.
