Editing Endometrium (section)

===Embryo transfer===
{{Anchor|Triple-line}}

An endometrial thickness (EMT) of less than 7&nbsp;mm decreases the pregnancy rate in [[in vitro fertilization]] by an [[odds ratio]] of approximately 0.4 compared to an EMT of over 7&nbsp;mm. However, such low thickness rarely occurs, and any routine use of this parameter is regarded as not justified. The optimal endometrial thickness is 10mm. Nevertheless, in human a perfect synchrony is not necessary; if the endometrium is not ready to receive the embryo an ectopic pregnancy may occur. This consist of the implantation of the blast outside the uterus, which can be extremely dangerous.<ref name="KasiusSmit2014">{{cite journal|last1=Kasius|first1=A.|last2=Smit|first2=J. G.|last3=Torrance|first3=H. L.|last4=Eijkemans|first4=M. J. C.|last5=Mol|first5=B. W.|last6=Opmeer|first6=B. C.|last7=Broekmans|first7=F. J. M.|title=Endometrial thickness and pregnancy rates after IVF: a systematic review and meta-analysis|journal=Human Reproduction Update|volume=20|issue=4|year=2014|pages=530–541|issn=1355-4786|doi=10.1093/humupd/dmu011|pmid=24664156|doi-access=free}}</ref>
[[File:Triple-line endometrium.jpg|thumb|''Triple-line'' endometrium measuring 7mm.]]
Observation of the endometrium by [[transvaginal ultrasonography]] is used when administering [[fertility medication]], such as in [[in vitro fertilization]]. At the time of [[embryo transfer]], it is favorable to have an endometrium of a thickness of between 7 and 14 [[millimeter|mm]] with a ''triple-line'' configuration,<ref name="ZhaoZhang2012">{{cite journal|last1=Zhao|first1=Jing|last2=Zhang|first2=Qiong|last3=Li|first3=Yanping|title=The effect of endometrial thickness and pattern measured by ultrasonography on pregnancy outcomes during IVF-ET cycles|journal=Reproductive Biology and Endocrinology|volume=10|issue=1|year=2012|pages=100|issn=1477-7827|doi=10.1186/1477-7827-10-100|pmid=23190428|pmc=3551825 |doi-access=free }}</ref> which means that the endometrium contains a [[hyperechoic]] (usually displayed as light) line in the middle surrounded by two more [[hypoechoic]] (darker) lines. A ''triple-line'' endometrium reflects the separation of the basal layer and the functional layer, and is also observed in the periovulatory period secondary to rising [[estradiol]] levels, and disappears after ovulation.<ref name="BaerwaldPierson2004">{{cite journal|last1=Baerwald|first1=A. R.|last2=Pierson|first2=R. A.|title=Endometrial development in association with ovarian follicular waves during the menstrual cycle|journal=Ultrasound in Obstetrics and Gynecology|volume=24|issue=4|year=2004|pages=453–460|issn=0960-7692|doi=10.1002/uog.1123|pmid=15343603|pmc=2891966}}</ref>

Endometrial thickness is also associated with live births in IVF. The live birth rate in a normal endometrium is halved when the thickness is <5mm.<ref>1. Gallos, I. D. et al. Optimal endometrial thickness to maximize live births and minimize pregnancy losses: Analysis of 25,767 fresh embryo transfers. Reprod. Biomed. Online 37, 542–548 (2018).</ref>