High pregnancy rates with minimum risk

Dr. Chenette's picture

High pregnancy rates with minimum risk

October 29, 2013

High pregnancy rates with minimum risk:
The new technology of CCS enables transfer of a single embryo while maintaining high pregnancy rates:

Building healthy families, one baby at a time, is our goal at Pacific Fertility Center.

Optimizing treatment outcomes is not just about high pregnancy rates. High success rates must be balanced by reducing risks. The goal is delivery of a healthy child in the fastest and lowest cost possible, while reducing risk of medical problems of pregnancy.

Comprehensive chromosome screening (CCS) is a new way of identifying the healthiest embryos for transfer after in vitro fertilization (IVF). This exciting new technology enables the routine transfer of a single embryo with very low risk, with dramatic improvements in implantation and pregnancy rates.

With CCS, it is possible to determine whether there is a balanced set of chromosomes, a euploid embryo, at an early stage of development. With a euploid embryo, a woman has an excellent chance of conceiving and carrying a healthy baby to term. In 2012, Pacific Fertility Center’s clinical pregnancy rate was 74.5 percent per transfer with CCS screened embryos in women 40 and under.

In addition to improving IVF pregnancy rates, CCS helps:

  • Enable elective single embryo transfer (eSET) in all age groups, reducing the risk of multiple gestation (twins and triplets)
  • Reduce the risk of miscarriage
  • Reduce the risk of chromosomal abnormalities such as Down syndrome

Problems in pregnancy
Miscarriage, multiple gestation, and clinical problems like Down syndrome and Turner syndrome all are possible problems that could occur in any pregnancy. These problems share a root cause—aneuploidy, an abnormal number of chromosomes in the embryo.

Usually 23 pairs of chromosomes (46 in total) are present in a normal euploid embryo. Girls have paired X chromosomes (46XX), and boys an X and a Y (46XY). When one or more chromosomes is duplicated or missing, aneuploidy is present. Examples are Trisomy 18, Trisomy 21 (Down Syndrome) and a missing X chromosome, 46XO, known as Turner Syndrome.

More often than not, aneuploid embryos do not grow, and are lost so early that a pregnancy test remains negative. A few that survive and implant result in miscarriage. Fewer still, those that make it past the first trimester, are responsible for clinical aneuploidy, for example Down Syndrome.

Comprehensive Chromosome Screening at Pacific Fertility Center
Pacific Fertility Center embryologists sample a few cells from an embryo 5 days after insemination, a day 5 blastocyst stage embryo. We use advanced techniques of Time-lapse video imaging, culture of embryos to the blastocyst stage, laser-assisted hatching and embryo biopsy. Embryos are then stored through a technique known as vitrification while awaiting test results from a genetics lab.

Healthy euploid embryos are identified as those with normal chromosomes. Only a handful of such embryos develop from each batch of eggs. Those that are euploid are warmed and transferred back to the mother a week after ovulation, in a natural or medicated cycle.

Euploid embryos are wonderfully effective at implanting and starting a pregnancy and can be transferred one at a time, with very high pregnancy rates.

Superior results from CCS at PFC
Outcomes in IVF cycles with CCS are clearly superior to those not using CCS:

  • Women 40 and younger achieved implantation rates of 70 percent or more at Pacific Fertility Center in 2012. The implantation rate of a biopsy-proven euploid blastocyst ranges by age. In those older than 40, implantation rates were 40 to 50 percent.
  • The miscarriage rates range from 6 to10 percent. These low pregnancy loss rates are one-third of the miscarriage rate in pregnancy at a similar age conceived naturally.
  • Single embryos can be transferred after CCS, reducing the risk of multiple gestation and avoiding the risks to pregnancy associated with multiple gestation.
  • Clinical aneuploidy, such as Down syndrome, is less common after CCS, reducing the need for invasive prenatal testing and reducing the need for the difficult decisions attending Down syndrome in pregnancy.

CCS at PFC
PFC uses a single nucleotide polymorphism (SNP) microarray with a proprietary technology called Parental Support™, from Natera, a San Francisco Bay Area company. The SNP microarray tags thousands of genetic sequences and correlates this data with parental test results and advanced error-correcting algorithms to provide a count of chromosomes in the embryo.

Not all IVF treatment cycles produce a euploid embryo. The major reason for this is cycle cancelation, usually from low egg production. Occasionally embryos do not develop to the blastocyst stage and cannot be biopsied. Occasionally all biopsied embryos are abnormal.

Euploid embryo yields are highly age-dependent. Euploid embryos are found in the majority of treatment cycles in younger women, with fewer available at older age groups. At Pacific Fertility Center in 2012, for egg donors under age 30, 7 euploid embryos were found per cycle on average. Cycles in women under 35 yielded 3 euploid embryos, declining to 1 euploid embryo at age 38 to 40 and less than 1 over age 40. For women 43 and above, few treatment cycles resulted in a euploid embryo.

In 2012, 101 biopsy-proven euploid embryos were transferred in 90 frozen embryo transfer cycles at Pacific Fertility Center. Most of those patients elected to transfer only 1 embryo. The overall implantation rate was 72 percent in women 40 and under and 54 percent in women over 40. The clinical pregnancy rate was 74.5 percent in women 40 and under, compared to 43.8 percent with traditional IVF.

In most cases, these high rates are achieved with transfer of a single embryo with a very low multiple gestation rate, reduced miscarriage rate, and reduced Down syndrome risk. PFC results are comparable to, and in some cases better than, those published by other major fertility centers in the country.

CCS is a method of embryo selection, that is, choosing the best embryo out of a group. CCS alone does not increase the number of normal embryos available for selection.

CCS is an effective way to select healthy embryos
In summary, CCS is an exciting new technology that permits selection of the healthiest embryos for transfer, improving implantation and pregnancy rates and reducing risk after in vitro fertilization. CCS allows single embryo transfer of healthy embryos after IVF, maximizing the chance of delivering a healthy baby while reducing multiple gestation, miscarriage risk, and clinical aneuploidy.

CCS is one more way Pacific Fertility Center is helping our patients grow their families, one healthy baby at a time.

- Philip Chenette, M.D.