Increasing the number of cycles of in vitro fertilization to more than three or four may boost success rates for infertile women up to the age of 42, according to a new study published in JAMA, with six IVF cycles producing the highest live birth rates.

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Six cycles of IVF were found to produce live birth rates of up to 68% in this latest study.

In vitro fertilization (IVF) is a form of assisted reproductive technology (ART) that involves manually fertilizing an egg with sperm in a lab dish and transferring the embryo to the uterus.

According to Resolve: The National Infertility Association, there is an average 20-35% success rate per cycle of IVF in the US, with the highest per-cycle success rates standing at around 40%.

Study leader Debbie A. Lawlor, PhD, of the University of Bristol in the UK, and her team note that the majority of women opt to stop IVF after experiencing around three or four unsuccessful cycles.

However, their research suggests continuing IVF after this point could boost success rates to as much as 68%.

To reach their findings, Lawlor and colleagues analyzed data of 156,947 women from the UK who underwent 257,398 cycles of IVF involving either fresh or frozen embryo transfers between 2003-10. Follow-up continued until June 2012.

Women in the study were a median age of 35 at the start of treatment, and the median infertility duration for all cycles was 4 years.

Six IVF cycles produced highest live birth rates

Overall, the live birth rate for the first IVF cycle for the women was 29.5%, and there was a live birth rate of at least 20% for each cycle up to the fourth cycle.

Fast facts about infertility
  • Around 1 in 8 couples in the US have problems getting pregnant or sustaining a pregnancy
  • Less than 3% of infertility cases need to be treated with ART; around 85-90% of cases can be treated with medications or surgery
  • Around 11.9% of women in the US have ever received infertility services in their lifetime.

Learn more about infertility

The team found that the cumulative prognosis-adjusted live birth rate over all cycles of IVF continued to rise right up until the ninth cycle, with a live birth rate of 65.3% identified for the sixth cycle.

Among women under the age of 40 who underwent IVF with their own oocytes, or eggs, the live birth rate was 32% for the first cycle and was at least 20% up to the fourth cycle. For the sixth cycle, however, a live birth rate of around 68% was achieved.

Women aged 40-42 years had a 12% live birth rate for the first cycle of IVF, while a live birth rate of 31.5% was achieved with six cycles.

For women over the age of 42, however, the live birth rates for each cycle were lower than 4%, and among women who used donor eggs for IVF, success rates did not differ by age.

Live birth rates were lower for women with untreated male partner-related infertility, compared with those whose infertility was caused by other factors, though this difference was offset by earlier treatment with sperm donation or intracytoplasmic sperm injection (ICSI).

The researchers note that women under the age of 40, those who used donor eggs and women with male partner-related infertility that was treated with sperm donation or ICSI achieved live birth rates after four or five cycles that were similar to those of women who conceive naturally within 12 months. "It should be noted, however, that, in these women, five cycles took a median of 2 years," they add.

Additionally, the team found that the number of eggs retrieved after ovarian stimulation in one IVF cycle has no impact on the live birth rates in following cycles. They say this finding is important as infertile couples are often told that their chances of success with future IVF cycles may be hindered if only a few or no eggs are retrieved in a previous cycle.

Commenting on their overall results, the researchers say:

"These findings support the efficacy of extending the number of IVF cycles beyond three or four."

Emotional, financial barriers to prolonged IVF

Lawlor and colleagues note that some couples may find prolonged IVF treatment emotionally stressful and financially costly, noting that several IVF cycles may be "unsustainable" for them, health services and insurers; one cycle of IVF costs around $14,000-$17,000, depending on the country and the treatment type used.

However, the team recommends that the possibility of success with additional IVF cycles be discussed with couples.

Dr. Evan Myers, of Duke University Medical Center in Durham, NC, agrees in an accompanying editorial, noting that it is important doctors share the study data with couples so they can make a "truly informed decision."

However, Dr. Myers cautions that the study data may not be generalizable to the US, pointing to differences in patient populations and utilization of ICSI in IVF, which is much higher in the US than the UK.

"Despite these limitations," he adds, "these findings suggest that, for some couples, especially those in whom the female partner is younger than 40 years, male-factor infertility is treated with ICSI, or oocyte or semen donation is used, the incremental increase in cumulative pregnancy probability after three or four ART cycles may be worthwhile, especially if financial resources are available."

In October, Medical News Today reported on a novel DNA test that researchers claim could boost IVF success rates to as much as 80%.