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High Pregnancy Rates with Single Embryo Transfer and Chromosome Screening

Woman with baby

Approximately three in four miscarriages are related to chromosomal error, and older women have a harder time getting and staying pregnant due to an increase in aneuploidy, an abnormal number of chromosomes. Fortunately, with a genetic screening technique called comprehensive chromosome screening (CCS), embryos are screened and chromosomes are counted with over 97 percent accuracy. “That’s really powerful for patients because not only can it help them to get pregnant more often, but it means we can put back fewer embryos,” says Dr. Thomas Molinaro. “Once we eliminate the embryos that aren’t going to get you pregnant, in our studies the take home baby rates are over 60 percent in women under 40.”

Molinaro is a reproductive endocrinologist with RMA of New Jersey. Their BEST Trial, published last year, set out to prove that CCS was the key to making single embryo transfer (SET) palatable. “The single worst thing I can do is give anybody twins,” he says. While many couples undergoing fertility treatment want twins, it’s harder on the mother and the baby, compared to a singleton birth. “She is more likely to deliver four-and-a-half weeks early, the rate of prematurity and low birth weight is much higher, and the healthcare dollars are four fold,” he says. “Infertility multiple gestations roughly cost this country one billion in healthcare dollars every year. We think that’s unacceptable.”

They key is to get good pregnancy rates with one embryo, and every study has shown two embryos are better than one, until this BEST study. “We can get similar pregnancy rates by doing chromosome screening and transferring one embryo at a time,” Molinaro says. In the randomized trial of patients under the age of 42, half the patients had a double embryo transfer of unscreened embryos and the other half did CCS and single embryo transfer. As the chart below illustrates, the live birth rate was comparable: 61% in single embryo transfer/CCS group compared to 65% in the double embryo transfer group, there were no twins in single embryo transfer group, miscarriage rates were lower, as were preterm delivery rate, total NICU days, and the birth weight was much higher. The cost for the double embryo transfer was almost twice as high.


Single Embryo Transfer/CCS

Double Embryo Transfer

  Live Birth Rate



  Twin Delivery Rate






  Preterm Delivery Rate



  Total NICU Days



  Birth Weight



  Mean/Delivery (28 days)


“This is our paradigm. You can maximize patient outcomes using CCS and single embryo transfer,” Molinaro says. “We’d like to see this technology available to everybody.”

RMA of New Jersey offers CCS to all patients and 60 to 65 percent of their cycles employ it. “I have no hesitation to do single embryo transfer for a 42-year-old if she’s doing chromosomal screening. The problem with being older is you make fewer embryos and sometimes they’re all abnormal," he says. "As a patient I would want to know that. I would want to know why it’s not working."

Molinaro does recognize that cost of CCS is a barrier; it’s an extra $3,000 to $4,000 on top of IVF costs. The cost will come down as the technology gets better, he says, and as the study demonstrates it can save you upwards of $40,000 in healthcare costs.


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