*Percentages are per embryo transfer.

Pregnancy is defined as the visualization of a pregnancy with vaginal ultrasound. Biochemical pregnancies, which are positive pregnancy test followed by a very early miscarriage, are not included.

Results may vary depending on if they are based on the number of started cycles or per embryo transfer. For various reasons, treatment can be stopped after stimulation has begun or there may not be any good quality embryos to transfer. Another important reason for not doing a fresh embryo transfer are cases when transfer is postponed (all embryos are frozen) to avoid a dangerous ovarian hyper-stimulation syndrome. This means that fewer individuals complete a treatment than those who start treatment. The number of pregnancies is higher per embryo transfer compared with pregnancies per total treatments started.

In an extensive collaboration with Uppsala University, we have systematically studied factors in the embryo that affect the chance of pregnancy. Additionally, we have methodically registered many different factors about the couples we have treated. Recently, we analyzed all of these factors using advanced statistical methods. This has resulted in two important improvements. We are able to evaluate which embryo will give the highest chance of pregnancy. Additionally, we are now able to give each individual couple a unique prognosis of their chance of pregnancy in IVF.

The single most important factor that determines if one will succeed in IVF is the woman’s age. Natural fertility decreases considerably already at 36-37 years of age compared with 20 years of age.  This is also reflected in IVF results. At an increasing age, egg quality is inferior, which leads to fewer pregnancies and increased miscarriage rates. We have an age limit for treating women over 42 years of age. The reason is that, just as in other clinics, treatment of women over this age results in extremely few pregnancies. There is also a high risk for miscarriage.

Even if age is the single most important factor for the chance of success, there is a wide biological variation between women, even for those who are at the age when pregnancy chance declines. Using ultrasound examination and various hormone analyses, we work scientifically to determine each couple’s anticipated results in order to individually tailor counseling.  

During the vaginal ultrasound examination, usually done at the first visit, the ovarian size and number of immature follicles within the ovaries are assessed. Pregnancy chance is greater for those with larger ovaries and many immature follicles. Correspondingly, a woman 39 – 40 years of age with large ovaries containing many follicles will have a similar chance of a successful treatment as a woman who is much younger who has smaller ovaries with fewer follicles.

The hormone analyses supplementing the ultrasound examination are Antimüllerian hormone (AMH) and, if needed, the pituitary hormones FSH and LH, which are taken as a blood sample early in the menstrual cycle.  The results of the hormone analyses, especially AMH, are an excellent estimation of the pool of eggs remaining within the ovaries and, thus, give a prognosis of the chance of success. These variables are used within the above mention prognostic computer model. Other measurements include the length of the menstrual cycle where longer cycles are more advantageous than shorter cycles.

We strive to optimize the chance of obtaining a healthy baby and minimize the risks during pregnancy for the mother.

Recently, there has been a reduction in the number of embryos transferred to the uterus. We follow the Swedish Board of Health and Welfare’s directive to transfer only one embryo in order to reduce the number of twins. Previously, two embryos were transferred routinely. However, background studies to this directive showed increased risks for the children if they were born as twins compared with singleton pregnancies (see Torbjörn Bergh, et. al., Lancet, vol 354, 1999, The Board of Health and Welfare (Socialstyrelsen) report 2000:4). For example, the risk for cerebral palsy is fourfold for twins. Please note, however, that these risks are the same as spontaneous twin pregnancies.

Currently, we transfer one embryo in approximately 70% of all treatments. Our unique mathematical models are the basis of our decision on how many embryos we can transfer.  We can determine if we increase the chance of pregnancy by transferring two embryos without raising the risk for twins. Additionally, we can determine if the chance of transferring only one embryo gives the same chance of pregnancy as transferring two. For further information, see One or two embryos?

With the help of our databased prognostic and selection model, our results continue to remain high. The implantation rate (the chance that an individual embryo develops into a pregnancy) is higher than before when routinely two embryos were transferred.  This is because we have developed better methods to help select the best embryo. Also, the number of treatments where the embryo can be frozen has increased significantly. Together, these developments have allowed the chance of pregnancy after egg retrieval (including the results from transfer of frozen/thawed embryos) to continue to remain just as high as when two embryos were routinely transferred at the same time. Simultaneously, the number of twin births was reduced from 28 % to 2 %, which is the lowest in Sweden. Most important though, is the dramatic reduction by 70 % of the number of children born with a low birth weight (a known risk factor for cerebral palsy). Additionally, the number of children who are stillborn or die shortly after birth has been reduced by 70%. These risks are now at the same levels as pregnancies that occur without treatment.

Please see more about this dramatic change in results under Science. Would you like to know how high your chances of a successful treatment at our clinic are? Please contact us. Most often, all that is needed to determine your prognosis is an ultrasound examination and blood test.

One method that has been tested to determine which embryo is best is blastocyst culture. This means that the embryo is cultured for five days instead of two. By then, the embryos should have developed into a blastocyst. Some embryos stop developing during this extended culture and only the strongest embryos remain. One cause is, of course, that not all embryos are of good quality and the longer they are cultured, it will be easier to determine which are of poorer quality.

We use our unique embryo scoring model to assess day 2 embryos and, thereby, have a very good method for choosing embryos to be transfered or frozen. We can objectively determine the risk for a twin pregnancy and, thus, are able to assess which cases to transfer two embryos.

For couples with fewer fertilized eggs, we usually chose to culture for two days. For those with many fertiized eggs, a longer time is advantageous in helping decide which embryo should be transfered. We have used both methods with excellent results for many years. Please see Blastocyst.