Embryo Selection after IVF

Embryo Selection after IVF

Embryo Selection after IVF

Many of human embryos produced after in vitro fertilization carry abnormal chromosomes. Placing a chromosomally normal embryo (s) into a normal uterus has a very high chance of achieving a pregnancy. Your eggs have been retrieved and the mature eggs were fertilized. Now You and your reproductive endocrinologist are faced with the critical task of how many and which embryo to transfer to the uterus or which ones to freeze.

Why do we Need Embryo Selection?

Selection of the most appropriate embryo(s) for transfer aim at i. Maximizing the chance for pregnancy and ii. Minimizing the risk of twins and other multiple pregnancies. Casual inspection of the embryo does not yield accurate information about its chromosome makeup. One can follow an indiscriminate approach where all embryos are transferred. The problem is this approach yields high unacceptable multiple pregnancy rates. On the other hand one can transfer one embryo at a time. This is a much safer approach in terms of markedly minimizing twin rates but may lower the chance for getting pregnant. In addition it also require a robust freezing program so that frozen embryos can survive thawing. Right now in The US the survival of frozen embryos exceed 95% and the chance for pregnancy with a thawed embryo is approximately equal to a fresh embryo.

Measure of Success: time to conceive or cumulative chance for pregnancy?

One major issue related to fertility treatment especially IVF is how to measure success? specifically consider this question: if you have three embryos and decided to transfer them one at a time and got pregnant after the third transfer with a singleton, how does that compare to transferring all embryos in the fresh cycle and getting pregnant in twins? before answering it is important to know that twin gestation is associated with higher risk for pre-term delivery, ICU admissions and long term consequences for the babies.

In other words should you consider success as pregnancy taking place after one retrieval (cumulative chance from fresh and frozen embryos) or pregnancy taking place in the fresh cycle only (fresh embryos)? In other words would you like to shorten the time to conceive at the expense of higher risk for multiple pregnancy? Within reason, this is a question for you and your reproductive endocrinologist to answer based on your preferences and his practice

You have a Voice: How should you use your embryos after IVF?

You need to have a voice in the number of embryos transferred to your uterus. Although your fertility specialist can discuss numbers and chances and other technical details as well as long term risks for multiple pregnancy, there are questions that cannot be answered by anyone but you.

  • How do you feel about twins? triplets and quads?
  • Would you accept fetal reduction (removal of one or more sacs from the uterus and leaving only one or two)?
  • Do you have the social support system to take care of twins?

For these and many other reasons your input in the number of embryos to transfer is paramount.

Methods of Embryo Selection after IVF

Embryo Morphology and Female Age

Age is, by far, the strongest predictor of the health of the embryos. Younger women produce more chromosomally normal embryos than older women. An embryo from a woman at age 30 commonly implants 40% of the time as opposed to 5% or less in a woman age 40. For any given cohort, embryos are graded based on specific morphological criteria from the best looking to the worst. These criteria are technical and followed by all embryologists. Embryos are prioritized for transfer based on their shape. Morphology, however is may be 50 to 60% predictive of pregnancy, far from ideal. The combined use of morphology of embryos, stage of development (day 3 or blastocyst) and age is the standard selection method for which embryo is transferred first and how many. This method has the advantage of being sheep, quick and non-invasive. All other methods must prove superior to morphology + age before adoption.

Extended Culture to Blastocyst Stage (Day 5 Embryo)

Keeping day 3 embryos in culture may give these embryos may time to develop to blastocysts. Presumably, the better embryos progress to blastocysts or do so faster than less healthy embryos, thus they are preferentially selected for transfer.

Time Lapse Imaging of Embryos

time lapse embryo imaging-normal embryo division

time lapse embryo imaging-normal embryo division

Embryos are placed in a specific incubator in a specific plate and is observed at predetermined time

time lapse embryo imaging-abnormal embryo division

time lapse embryo imaging-abnormal embryo division

points using time lapse microscopy / photography. Photos are analyzed manually or through a computer and embryos are graded based on timely division of blastmeres (component cells). There is no evidence so far that pregnancy rate is improved above using morphology. There is extra cost associated with the use of the special plate and is also limited by the number of special incubators available.

PGS (Embryo Chromosome testing)

New forms of PGS (performing biopsy at the blastocyst stage) and more accurate platforms for analyzing the biopsied cells are available. However, the concept that better selection will lead to improved IVF results is far from certain.

It success of an IVF cycle is measured after transfer of fresh then frozen embryos till pregnancy ensues (cumulative success) ad patients are will to be patient for 1-2 more months, then any form of embryo selection, PGS or otherwise, will not improve the live birth rates. Moreover, PGS can be harmeful as it may misdiagnose the health of the embryos (see this article on PGS for details). PGS increases the expense of treatment $4000 to 6000

Embryo selection is maybe be able to improve the time to pregnancy, if embryos with the highest implantation potential are transferred first.

Based on the available evidence, judicious selection of embryos based on patient age, morphology and the use of extended culture to blastocysts are the standard of care in embryo selection after IVF. Two additional factors to consider is how robust is the freezing program of that specific lab (generally excellent all over the US) and the acceptability of fetal reduction by the couple. Liberal use of single embryo transfer when appropriate should be strongly considered. ‘New’ ideas should be subjected to rigorous scientific evaluations ‘fertility clinical trials’ before they are ready for routine use. Thus far, based on published evidence, embryo time lapse imaging and PGS should remain investigational.


Frozen Embryo Transfers (FET)

Frozen Embryo Transfer

Following IVF, excess embryos are frozen for use with second attempts if no pregnancy takes place or to conceive a second child. With improvement of the freezing and thaw techniques: the majority of frozen embryos survive thawing, the implantation potential of a thawed embryo is comparable to a fresh embryo, less embryos or single embryo can be transferred in the fresh cycle and selection of the best embryo for fresh transfer became less important.

Frozen embryo transfer: blastocysts and cleavage embryos can be vitrified after IVF

Frozen embryo transfer (FET)

Freezing of embryos allow ample time for genetic testing of embryos if needed, transferring embryos to a different locale, delaying transfer due to medical problem, the emergence of an abnormality in the lining of the uterus e.g thinĀ  endometrium, polyp, fluid.. or till a gestational carrier is found.

Benefits of Frozen Embryo Transfer

1. Pregnancy rate after frozen embryo transfer is comparable to fresh transfer and may even be higher than fresh transfer in some studies. More work is needed to confirm higher live birth rate.

2. Complications: frozen embryo transfer minimize some of the complications related to IVF. Ovarian hyperstimulation syndrome (OHSS) and possibly ectopic pregnancy (pregnancy in the fallopian tube)

3. Lower risk for pregnancy complications and better quality baby: frozen transfer appear to reduce the risk for preterm delivery, bleeding in pregnancy and low birth weight, possibly due to better placental function.

How is the lining of the uterus prepared for frozen embryo transfer?

1. Natural cycle: in ovulating women, the follicle in the ovary is monitored till the point of ovulation is accurately identified. The follicle will internally produce the estrogen required to build the lining. When ovulation takes place, the embryos are thawed and transferred in a day comparable to its age e.g a day 5 embryo is transferred 5 days after ovulation. This process require only ultrasound and blood work monitoring

2. Estrogen replacement cycle: ovulation is stopped and estrogen is supplemented externally (patches,oral or vaginal) till the desired thickness and pattern of the uterine lining. Progesterone is then started (injection or vaginal) then embryos are transferred.

Timing of thaw and transfer is a complicated question and it depends on the type of cycle and age of embryos. Sometimes embryos are thawed and cultured for few days before transfer

All method for endometrium preparation yield similar pregnancy rate. At NYCIVF we prefer natural cycle with luteal phase support using vaginal estrogen.

What makes a frozen embryo transfer cycle successful?

Embryo quality: one or more top quality embryo morphology observed at any stage of culture improves the outcome even if high-quality characteristics disappeared before transfer. Transferring more than one embryo increases the pregnancy rate but also multiple pregnancy.

Conclusion: should you intentionally delay transfer to frozen cycle? no but if you need to freeze the embryos, expect similar pregnancy rate as in the fresh cycle.

IUI or IVF for Unexplained Infertility

IUI or IVF for Unexplained Infertility

Choosing IUI or IVF for unexplained infertility can be confusing. If you have been trying to conceive for several years and initial fertility tests does not reveal any abnormalities (open fallopian tubes, normal sperm and regular ovulation), you will be diagnosed with unexplained or idiopathic infertility.

Possible treatments include ovarian stimulation-IUI or IVF

What should you consider before deciding between IUI and IVF?

IVF In Vitro Fertilization

IVF In Vitro Fertilization


Intrauterine Insemination (IUI)

Intrauterine Insemination (IUI)

  1. Pregnancy rate: IVF is associated with higher pregnancy rate than IUI, approximately 3 times. In women less than 35 pregnancy rate is approximately 50% with 2 embryo transfer and 35% with one embryo transfer versus 10-15% per one cycle of IUI.
  2. Multiple pregnancies: When ovulation is stimulated using injection medications (FSH) the chance for twins is about 30% and higher orders multiple pregnancies 1-3%. Multiple pregnancies is associated with increased risk of preterm delivery with possible long term effects on the newborns. Compared to IVF with single embryo transfer, the chance for twins is 1% and higher order multiples is very low. Actually IVF with single embryo transfer is the more conservative approach in women at risk for multiple pregnancies with IUI.
  3. Cost: IVF is more costly due to the requirement of lab procedures to fertilize the eggs and culture the embryos. If multiple pregnancies at it complications are factored in IVF with single embryo transfer appears to the cheaper approach.

Sound evaluation by a reproductive endocrinologist can give you the advice and guide you through the decision.

Women with high ovarian reserve as PCOS are better served in general by avoiding injection medication + IUI and proceed to IVF if oral medication e.g clomid do not succeed. Women with reduced ovarian reserve generally will have a high odds for getting pregnant with IVF than IUI.


Avoiding Twins Following Fertility Treatment

Avoiding Twins Following Fertility Treatment

Avoiding Twins Following Fertility Treatment requires careful consideration of fertility treatment options

Many couples try to avoid twins for many reasons:

  1. Baby related: preterm delivery, before 37 weeks, that may result in prematurity, need for a long intensive treatment and possible neurological impairment and other diseases.
  2. Mother related: twin pregnancy is more risky than singleton.
  3. Social reasons: financial, emotional and personal burdens on the family

Counseling from reproductive endocrinologists about the risk of multiple pregnancy is very important before initiating fertility treatment.

Twins can be avoided with fertility treatment (Selective Reduction) by avoiding injection medications during IUI cycles, single embryo transfer during IVF cycles and fetal reduction if twin pregnancy takes place.

Twins can be avoided with fertility treatment (Selective Reduction) by avoiding injection medications during IUI cycles, single embryo transfer during IVF cycles and fetal reduction if twin pregnancy takes place.

The chance for twin pregnancy following fertility treatment can be minimized or avoided if one

  • Avoid treatments that cause multiple embryos to reach the uterus and / or
  • Fetal reduction of twins to singleton

Avoiding Twins Following Fertility Treatment : do not allow multiple embryos to reach the uterus

Fertility treatments include IUI and IVF.

  1. IUI. The ovaries are stimulated for 10 days or so then sperm is concentrated and injected inside the uterus. Risk for twins increase with the use of injection medication (30%) versus oral medicine (clomid 8%). The risk is also higher in the first cycle versus later cycles, in younger women, wemen with PCOS, when many large follicles (> 14mm) on ultrasound and with high estrogen levels. Even when with meticulous monitoring of stimulation, the risk of twins is not zero.
  2. IVF. The ovaries are stimulated and retrieved, fertilized in the lab then one or more embryos are transferred in the uterus. The number of embryos transferred is selected based on the implantation potential per embryo. Embryo implantation is related to female age and morphology or shape of the embryo. When one embryo is transferred (elective single embryo transfer) the risk for twins is (1%) due to embryo splitting versus about 30% when two embryos are transferred. The American Society for Reproductive Medicine recommend single embryo transfer for younger women with good quality embryos. Single embryo transfer should be considered for all women who want to avoid twins.

Avoiding Twins Following Fertility Treatments : Fetal Reduction

Fetal reduction means one pregnancy sac is removed from the uterus while the other sac is left. First there is the option is of CVS. The sacs are sampled and tested for their chromosomes to select the normal ones. The procedure of reduction is performed using a needle not surgery. Studies showed that reduction prolongs pregnancy and improve survival and quality of the remaining babies even when 5% chance of loosing both babies due to the procedure is considered. This is not abortion. This is an attempt to give the remaining babies better chance at survival and healthy life.

Conclusion: Know your personal risk for multiple pregnancy, Avoid using injection medication for IUI, consider single embryo transfer after IVF and if pregnant with twins consider fetal reduction.