The role of frozen–thawed embryo replacement cycles in assisted conception TOG 2019

Question 1

Graph showing how multiple pregnancy, fresh cycles and fozen cycles live birth rate have changed

Answer 1

Frozen-thawed embryo replacement now have better prengnancy rates.

Question 2

Indications for freezing all suitable embryos

Answer 2

Acute (unplanned) freeze-all

Ovarian hyperstimulation syndrome
Uterine abnormality identified during ovarian stimulation (e.g. endometrial polyp identified during the cycle, fluid in the endometrium)
Complications of egg-collection procedure (e.g. intraperitoneal bleeding, damage to viscera, pelvic infection)
Social factors (unable to attend embryo transfer or need to defer pregnancy)
Raised progesterone on day of trigger injection (continuing research)
Planned freeze-all

Pre-implantation genetic testing
Fertility preservation
Recurrent implantation failure (continuing research)

Question 3

Rate of OHSS with fresh transfer and and freeze all transfer

Answer 3

Fresh 7%
Freeze all 1-3%

Question 4

Advantage and disadvantage of natural cycle frozen-thawed embryo replacement

Answer 4

Advantages:
No need for medication (avoids adverse effects and concordance issues)
May be cheaper than medicated frozen–thawed embryo replacement (FER)

Disadvantages:
Involves intensive ultrasound and endocrine monitoring
Requires ovulation
No control over day of embryo transfer, as fixed according to ovulation (so embryo transfer may be over a weekend)
Cancellation rate around 8–15% of started cycles

Question 5

Advantage and disadvantage of mediation frozen-thawed embryo replacement

Answer 5

Advantages:
Permits embryo transfer in anovulatory women
Allows choice over day of embryo transfer, which is convenient
In the case of ‘thin endometrium’, the dose and route of estrogen can be modified
Woman may feel more in control of events
Relatively low cycle cancellation rate (1–2%)

Disadvantages:
Prolonged course of medication
Medication may have adverse effects
More expensive than natural cycle FER

Question 6

Advantage and disadvantage of Ovarian stimulation frozen–thawed embryo replacement

Answer 6

Advantages:
Permits embryo transfer in anovulatory women who do not want standard medicated FER
May involve fewer days of medication than standard medicated FER
Relies on endogenous estradiol, so it may be beneficial in those with absorption issues

Disadvantages:
Requires intensive monitoring
Medication can cause adverse effects (e.g. injection site reactions or infections)
Gonadotrophins are associated with a risk of ovarian hyperstimulation syndrome
Clomifene may have an adverse effect on the endometrium
Gonadotrophins are expensive

Question 7

What is the minimum endometrial thickness for embryo transfer

Answer 7

7mm
Higher pregnancy rates if 9-14mm

Question 8

How to calculate gestational age with embryo transfer?

Answer 8

2 weeks + age of embryo
(2 weeks + 5 days for blastocyst)