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Single Embryo Transfer - An Overview

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Single embryo transfer (SET) is an effective ART (assisted reproductive technology) procedure. This article explains SET in detail.

Written by

Dr. Asha. C

Medically reviewed by

Dr. Richa Agarwal

Published At March 2, 2023
Reviewed AtMay 6, 2024

What Is Single Embryo Transfer?

Single-embryo transfer also called elective single-embryo transfer (eSET), is a procedure in which an embryo with better pregnancy success rates is selected from a larger number of embryos and transferred to the uterus. The embryo selected for SET might be from an IVF (in-vitro fertilization) done previously or from the current fresh IVF cycle that has more than one embryo. The embryos that are left behind may be kept aside for future use or cryopreservation (a process in which cells, tissues, or organs are preserved by cooling them to very low temperatures). This procedure helps women avoid risks to their own health by carrying multiple births. Babies born in multiple births are often smaller than their gestational age (low birth weight) or premature babies (born early) and experience adverse health outcomes than singleton infants.

Who Should Undergo Single Embryo Transfer?

Single embryo transfer is an ideal option for women who match the following criteria:

  • Women younger than 35 years of age.

  • Women undergoing the first assisted reproductive technology (ART) cycle.

  • Women who are able to produce a high number of good-quality embryos.

  • If additional quality embryos are available for cryopreservation.

  • Women who are healthy.

The women who meet the above criteria have a higher possibility of having multiple pregnancies. So by performing this procedure, the risks of multiple pregnancies can be avoided. If a woman has a choice of one or multiple embryos transferred should consider her and her partner’s personal and practical limits regarding raising a child. For instance, women who are planning to breastfeed exclusively find it hard if they have twins or triplets. Even the financial and practical aspects of childcare should also be taken into consideration.

Multiple pregnancies can cause several risks for both mother and child. A woman who has multiple pregnancies has a high risk of pregnancy complications, like hypertension, pre-eclampsia, gestational diabetes, and miscarriage. They are highly prone to having a cesarean delivery and will be faced with a greater risk of hemorrhage and anemia after delivery. And even some studies show a higher risk of postpartum depression for women carrying multiple babies.

Babies born with multiple pregnancies also carry multiple risks. Twins and triplets often have low birth weights when compared to singletons and also have an increased risk of being born prematurely. Thus, a SET procedure increases the chance of giving birth to a healthy baby.

How Is Single Embryo Transfer Performed?

During this procedure, the embryologists will choose the optimal quality embryos which are produced during the previous or fresh IVF cycle. Embryos that are not selected are then frozen for storage. The freezing and storing of an embryo will not lower the quality of an embryo. In fact, a good-quality embryo is more likely to survive the complete process of freezing and thawing. After selecting the embryo, it can be implanted back into the mother's womb. However, the time of embryo transfer may have an impact on the procedure’s success. The healthcare professional waits till the embryo is at its blastocyst stage, which happens on the fifth or sixth day, before implanting the embryo to increase the chances of success.

The transfer of embryos back to the uterus is by passing them through a catheter which is inserted into the vagina. The health care professional then proceeds to gently pass the catheter into the uterus through the cervix. The whole process is guided by an ultrasound image. The procedure is similar to a cervical screening exam. This procedure does not usually require any form of anesthesia. However, in some patients, mild sedation may be provided. Then there will be four to six hours of the recovery period, during which the patient is asked to lie flat on her back and remain relaxed. After this, the patient is discharged. The doctors will provide instructions to follow and continuous supplementation of progesterone.

What Are the Benefits of Single Embryo Transfer?

Single embryo transfer helps in avoiding the risks to mother and child, like hypertension, pre-eclampsia, gestational diabetes, and miscarriage. This procedure not only improves successful conception but also reduces complications like-

  • Premature delivery.

  • Miscarriage.

  • Disabilities in babies such as cerebral palsy and vision loss.

  • Complications to the mother include high blood pressure, nausea, and vomiting.

How Is the Best Embryo Selected for the Procedure?

The highest-quality embryo to transfer is selected by the laboratory based on its appearance. This procedure includes looking at the size and number of the cells, the development rate, and other factors. The selection criteria vary from laboratory to laboratory based on the different grading systems. The system also differs depending on the evaluation of the embryo in the cleavage or the blastocyst stage. However, no method can accurately predict which embryo will produce live offspring. Recently new techniques have been programmed by investigators to find the best embryo, such as tests to find out if an embryo is genetically normal. The help to increase pregnancy rates of the new technique is not yet known.

What Are the Complications of Selected Embryo Transfer?

A single embryo transfer does not decrease the chance of successfully conceiving a baby, but also it decreases the risk of multiple births and the risks associated with multiple pregnancies. Hence, the procedure is often considered the safer choice and is free from any possible complications or serious risks. The procedure is a very simple one with very few risks, like the following:

  • The loss of embryos during the transfer.

  • Implanting the embryo in the wrong location, like the fallopian tubes.

The risk factor for the women undergoing this procedure is almost nil. The patient may experience mild cramping sometimes. This procedure is actually considered the final and simplest step of the IVF process, after which the couple needs to wait for the results.


SET is an effective procedure with a good success rate. This is a very simple procedure in which an embryo with more success rate is selected for fertilization. It is helpful in avoiding the complications of multiple pregnancies in both mother and the child. The complication of this procedure is very minimal.

Dr. Richa Agarwal
Dr. Richa Agarwal

Obstetrics and Gynecology


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