Editing Multiple birth (section)

===Prevention in IVF===
Today many multiple pregnancies are the result of [[in vitro fertilisation]] (IVF). In a 1997 study of 2,173 [[embryo transfer]]s performed as part of [[in vitro fertilisation]] (IVF), 34% were successfully delivered pregnancies.<ref name="Elsner-1997">{{Cite journal |vauthors=Elsner CW, Tucker MJ, Sweitzer CL, Brockman WD, Morton PC, Wright G, Toledo AA |year=1997 |title=Multiple pregnancy rate and embryo number transferred during in vitro fertilization |journal=Am. J. Obstet. Gynecol. |volume=177 |issue=2 |pages=350–355; discussion 355–357 |doi=10.1016/S0002-9378(97)70197-2 |pmid=9290450}}</ref> The overall multiple pregnancy rate was 31.3% (24.7% twins, 5.8% triplets, and .08% quadruplets).<ref name="Elsner-1997" /> Because IVFs are producing more multiples, a number of efforts are being made to reduce the risk of multiple births- specifically triplets or more. Medical practitioners are doing this by limiting the number of embryos per embryo transfer to one or two. That way, the risks for the mother and fetuses are decreased.

The appropriate number of embryos to be transferred depends on the age of the woman, whether it is the first, second or third full IVF cycle attempt and whether there are top-quality embryos available. According to a guideline from The [[National Institute for Health and Care Excellence]] (NICE) in 2013, the number of embryos transferred in a cycle should be chosen as in following table:<ref name="Fertility">{{Cite web |date=February 2013 |title=Fertility: assessment and treatment for people with fertility problems |url=http://guidance.nice.org.uk/CG156 |url-status=live |archive-url=https://web.archive.org/web/20130223023043/http://guidance.nice.org.uk/CG156 |archive-date=2013-02-23 |access-date=2024-03-31 |website=National Institute for Health and Care Excellence (NICE) guidelines |ref=NICE clinical guideline CG156}}</ref>

{|class="wikitable"
|-
! Age !! Attempt no. !! Embryos transferred
|-
|rowspan=3| <37 years || 1st || 1
|-
| 2nd || 1 if top-quality
|-
| 3rd || No more than 2
|-
|rowspan=3| 37–39 years ||rowspan=2| 1st & 2nd || 1 if top-quality
|-
| 2 if not top-quality
|-
| 3rd || No more than 2
|-
| 40–42 years ||  || 2
|}

Also, it is recommended to use single embryo transfer in all situations if a top-quality blastocyst is available.<ref name="Fertility" />