4. Obstetrics p87-91 (Early pregnancy)

Question 1

Pregnancy - vocab (3)

Answer 1

Menstrual age = Embryologic age + 14 days
Embryo = 0-10 weeks menstrual age
Foetus = >10 weeks menstrual age

Question 2

Abortion - vocab (5)

Answer 2

Threatened abortion = Bleeding with closed cervix.
Inevitable abortion = cervical dilatation and/or placental and/or foetal tissue hanging out
Incomplete abortion = residual products in uterus.
Complete abortion = all products out
Missed abortion = Foetus is dead, still in uterus

Question 3

Intradecidual sign (4)

Answer 3

Earliest gestational sac.
When covered by echogenic decidua, it’s characteristic of early pregnancy.
Can be seen around 4-5 weeks.
Want to see a thin echogenic line of the uterine cavity passes by (not stops at) the sac to avoid calling a little bit of fluid in the canal a sac.

Question 4

Double decidual sac sign (4)

Answer 4

Another positive sign of early pregnancy.
Produced by visualising layers of decidua.
Decudua Vera (thicker, outer) and Decidua Capsularis (thinner, inner), with small amount of fluid inbetween.

Question 5

Yolk sac (4)

Answer 5

First visible structure within the gestational sac.
Seen when GS measures 8mm in diameter.
Should be oval or round, fluid filled and <6mm.
Yolk sac is located in chorionic cavity, connected to umbilicus of the embryo by vitelline duct.

Question 6

Yolk sac pathology (2)

Answer 6

Shouldn’t be too big (>6mm) or too small (<3mm).
Shouldn’t be solid or calcified.

Question 7

Amnion (2)

Answer 7

Membranes of the amnionic sac and chorionic space typically remain separated by thin layer of fluid until 14-16 weeks, when they fuse.
If amnion is disrupted before 10 weeks, foetus may cross into chorionic cavity and get tangled up in fibrous bands (amniotic band syndrome), can cause decapitation, limb amputation etc.

Question 8

Double bleb sign (2)

Answer 8

Earliest visualisation of the embryo.
2 fluid filled sacs (yolk and amniotic), with flat embryo in the middle.

Question 9

Crown Rump length (2)

Answer 9

Typically used to estimate gestational age, more accurate than menstrual history.
Embryo normally visible at 6 weeks.

Question 10

Anembryonic pregnancy (2)

Answer 10

Gestational sac without an embryo.
If seen, it’s either very early pregnancy or non viable pregnancy.
Should see the yolk sac at 8mm. Large gestational sac (>8-10mm) without a yolk sac, and a distorted contour is pretty reliable for non viable pregnancy.

Question 11

Pseudogestational sac (2)

Answer 11

Seen in presence of ectopic pregnancy.
A little blood in the uterine cavity with surrounding bright decidual endometrium (stimulated by pregnancy hormones)

Question 12

Guidelines for foetal demise (8)

Answer 12

Diagnostic of pregnancy failure
- Crown-rump length of <7mm and no heart beat
- Mean sac diameter of >25mm and no embryo
- No embryo with heartbeat >11 days after scan showing gestational sac with yolk sac.
- No embryo with heartbeat 2 weeks after a scan showing gestational sac without a yolk sac
Suspicious for pregnancy failure
- No embryo >6 weeks after last menstrual period.
- Mean sac diameter of 16-24mm and no embryo
- No embryo with heartbeat 13 days after a scan that showed a gestational sac without a yolk sac
- No embryo with heartbeat 10 days after a scan that showed a gestational sac with a yolk sac

Question 13

Subchorionic haemorrhage (4)

Answer 13

Common. Percentage of placental detachment is most important prognostic factor for foetal survival.
>2/3 circumference haematoma has 2x risk of abortion.
Women over 35 have worse outcomes
Implantation bleeding: small subchorionic haemorrhage occurring at the attachment of the chorion to the endometrium.

Question 14

Risk factors for ectopic pregnancy (6)

Answer 14

Hx of PID,
Tubal surgery,
Endometriosis,
Ovarian induction,
Previous ectopic,
Use of an IUD

Question 15

Ectopic pregnancy (4)

Answer 15

Usually (95%) occurs near fallopian tube, usually isthmus.
Can rarely occur in the developing portion of the tube which passes through the uterine wall (termed Interstitial).
Interstital ones are high risk, can grow large before rupture, causing catastrophic haemorrhage.
Can also rarely have implantation sites in the abdominal cavity, ovary and cervix.
Consider ectopic if positive bHCG. Normal doubling time makes ectopic less likely.

Question 16

Ectopic pregnancy - diagnosing (3)

Answer 16

If positive bHCG:
Live pregnancy/yolk sac outside the uterus = diagnostic for ectopic.
Nothing in the uterus + anything on the adnexa (other than corpus luteum) = 75-85% PPV for ectopic.
Nothing in the uterus + moderate free fluid = 70% PPV (more risk if fluid is echogenic.

Question 17

Tubal ring sign (2)

Answer 17

Echogenic ring surrounding an unruptured ectopic pregnancy.
Useful sign of ectopic pregnancy, 95% specific.

Question 18

Heterotopic pregnancy (2)

Answer 18

Baby in uterus and baby in tube (or other ectopic location).
Rare, usually only seen in women taking ovulation drugs or previous Hx of PID.