The More the Merrier, Cheaper by the Dozen?

Be Careful What You Wish For!

Posted Jul 20, 2014

The More the Merrier, Cheaper by the Dozen?

Be Careful What You Wish For!

Joann Paley Galst, PH.D.

From approximately 1915, the earliest year from which reliable data are available, until 1980, there was a 2% rate of twin births (i.e. about one in 50 babies). Over the years, that rate began to climb – until now, approximately one in every 30 babies born is a twin. What is causing this jump in multiple births?

Women are marrying later in the United States than in the past. As a result, they are also having children later and older women tend to conceive twins more frequently than younger women. This accounts for 1/3 of the increase in twin births. The rest is due to infertility treatment (both in vitro fertilization and fertility drugs). The increase in twin birth rates, however, does seem to be leveling off according to CDC reports and this is due, in part, to the push towards transferring fewer embryos in an IVF cycle. Single embryo transfer (SET) is a trend that was unheard of in earlier decades in the US, despite being encouraged in European countries for some time already. Thus, the increase in the twin birth rate has been slowed in the U.S. but has not yet been reversed.

Many prospective parents undergoing fertility treatment are highly resistant to the idea of SET. Their reasons are varied:

After waiting so long to have a child, getting a completed two-child family at once is enticing.

Finances come into play – and with “two for the price of one,” many parents embrace the idea of getting “more bang for their buck.”

Lack of insurance coverage – Since many insurance policies do not cover IVF, many prospective parents can only afford one cycle of IVF and since success rates are higher when two embryos are transferred, they want to have the best chance possible for a successful cycle with at least one take-home baby.

All of the above reasons have merit and validity. But many prospective parents are unaware of the realities of twin births:

• Harder pregnancies – increased rates of pregnancy induced hypertension/pre-eclampsia, gestational diabetes, anemia, and cesarean section.

• Harder births – increased likelihood of pre-term births and low birth weight babies, increased maternal blood loss during delivery.

• Harder parenting – increased rates of birth defects and long-term medical problems for babies; increased likelihood of infant death during the first year of life; higher rates of maternal depression and guilt as mothers report feeling they do not have adequate time to attend to either baby individually.

Merely looking at an embryo under a microscope to determine its shape and fragmentation level doesn’t offer enough information about the embryo’s fitness to predict successful implantation. Advances in chromosome testing of embryos can help determine which embryos give a woman the best shot at having a healthy baby, for example, preimplantation genetic screening in which a cell or two is removed from the embryo for analysis. This procedure, however, adds many thousands of dollars to the cost of an IVF cycle, is not usually covered by insurance, and may damage the embryo.

A new non-invasive embryo selection technique uses computer-automated time-lapse imaging, taking thousands of pictures of the growing embryo in the petri dish during incubation to study the development pattern and morphology of the embryo. This may allow determination of the chromosomal fitness and viability of an embryo without having to remove any cells or disturb the embryo in the incubator (exposure through removal of the embryo from the temperature-controlled incubator for observation by an embryologist can potentially damage the embryo), making it both safer to analyze embryos and contribute to a greater likelihood of IVF success rates with transfer of only one embryo at a time. In addition, it may be done at a lesser cost for prospective parents, although this technique is also unlikely to be covered by health insurance. Each IVF clinic would analyze the time-lapse images themselves and since clinics differ in how they culture embryos, timing of cell division events can differ between clinics thus making it difficult to develop an algorithm that could be applicable for all clinics.

Results thus far are exciting, but studies have used sample sizes too small to be definitive. Stay tuned for a further accumulation of data to see if this system actually improves pregnancies and live birth rates. That would be a most welcome advancement for those considering IVF and would support the greater safety of a singleton pregnancy.

Until this happens, additional changes are needed in policy and practice to help reduce multiples:

Expand insurance coverage for IVF (since pregnancy rates after double embryo transfer [DET] are similar to the cumulative pregnancy rates after two SET cycles).

Change the definition of a cycle of IVF to a stimulated cycle with IVF followed by consecutive SETs until a pregnancy is achieved. This would reduce the pressure on reproductive endocrinologists, wanting to keep their success statistics attractive to potential patients, to transfer more embryos for higher success rates while also reducing the rates of multiple births.

Improve communication to patients regarding the risks and benefits, both to mothers and babies, of available treatments. Research demonstrates that when patients are better informed, the decision for multiple embryo transfer is reduced.

Continue research to improve fertility treatment and identify embryos most likely to result in a live birth.

For further reading, see:

ASRM booklet (2012) on multiple gestations, available at

ASRM Fact Sheet on Fertility Drugs and the Risk of Multiple Births, available at

Current ASRM guidelines on maximum number of embryos to transfer

                                  Maximum Number of Embryos to Transfer

Cleavage-stage Embryos (day 2 or 3 embryo transfer)

                                  Age < 35          Age 35-37      Age 38-40      Age >40

Favorable Prognosis   1-2                           2                      3                  5

All others                      2                             3                      4                  5

                                 Maximum Number of Embryos to Transfer

 Blastocyst Embryos (day 5 or 6 embryo transfer)

                                 Age < 35           Age 35-37         Age 38-40     Age >40

Favorable Prognosis     1                             2                         2               3

All others                       2                             2                         3               3

Source: The Practice Committee of the American Society for Reproductive Medicine and the Practice Committee of the Society of Assisted Reproductive Technology. Criteria for number of embryos to transfer: a committee opinion. Fertility and Sterility, 2013; 99(1): 44-46. Available from:

Note: a favorable prognosis includes maternal age under 35, having excess high quality embryos available for cryopreservation from an IVF cycle, first or second treatment cycle, a previously successful IVF cycle, or being the recipient of embryos from donor eggs.

About the Author

Joann Paley Galst, Ph.D. is a cognitive-behavioral psychologist in New York specializing in mind-body medicine and reproductive health issues.

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