{"id":39489,"date":"2025-06-23T12:58:20","date_gmt":"2025-06-23T10:58:20","guid":{"rendered":"https:\/\/urecentrogutenberg.es\/eggs-classifications-how-we-classify-eggs-in-in-vitro-fertilisation\/"},"modified":"2025-11-13T14:01:39","modified_gmt":"2025-11-13T13:01:39","slug":"eggs-classifications-how-we-classify-eggs-in-in-vitro-fertilisation","status":"publish","type":"post","link":"https:\/\/urecentrogutenberg.es\/en\/eggs-classifications-how-we-classify-eggs-in-in-vitro-fertilisation\/","title":{"rendered":"Eggs classifications: How we classify eggs in In Vitro Fertilisation?"},"content":{"rendered":"<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_85 counter-hierarchy ez-toc-counter ez-toc-custom ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Tabla de contenidos<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #3f3f3f;color:#3f3f3f\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #3f3f3f;color:#3f3f3f\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/urecentrogutenberg.es\/en\/eggs-classifications-how-we-classify-eggs-in-in-vitro-fertilisation\/#What_is_an_egg_cell\" >What is an egg cell?<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/urecentrogutenberg.es\/en\/eggs-classifications-how-we-classify-eggs-in-in-vitro-fertilisation\/#How_eggs_cells_work\" >How eggs cells work?<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/urecentrogutenberg.es\/en\/eggs-classifications-how-we-classify-eggs-in-in-vitro-fertilisation\/#How_we_classify_eggs_in_In_Vitro_Fertilisation\" >How we classify eggs in In Vitro Fertilisation<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/urecentrogutenberg.es\/en\/eggs-classifications-how-we-classify-eggs-in-in-vitro-fertilisation\/#What_does_an_egg_look_like_when_we_obtain_it_through_assisted_reproduction\" >What does an egg look like when we obtain it through assisted reproduction?<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/urecentrogutenberg.es\/en\/eggs-classifications-how-we-classify-eggs-in-in-vitro-fertilisation\/#How_we_know_if_the_eggs_that_have_been_retrieved_are_mature\" >How we know if the eggs that have been retrieved are mature<\/a><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><ul class='ez-toc-list-level-4' ><li class='ez-toc-heading-level-4'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/urecentrogutenberg.es\/en\/eggs-classifications-how-we-classify-eggs-in-in-vitro-fertilisation\/#Do_you_have_any_other_questions_about_assisted_reproduction\" >Do you have any other questions about assisted reproduction?<\/a><\/li><\/ul><\/li><\/ul><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"What_is_an_egg_cell\"><\/span>What is an egg cell?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><strong>Eggs are sex cells, or the female gametes, which carry the genetic material a woman will pass on to her children.<\/strong>\u00a0At first glance, eggs are large, spherical cells that are produced\u00a0<a href=\"https:\/\/urecentrogutenberg.es\/en\/what-are-the-main-phases-of-the-menstrual-cycle\/\" target=\"_blank\" rel=\"noopener\">approximately every 28 days<\/a>\u00a0in the female\u2019s ovary. And as you already know, eggs play a fundamental role in the early stages of embryo development, and of course in assisted reproduction.<\/p>\n<h3><span class=\"ez-toc-section\" id=\"How_eggs_cells_work\"><\/span>How eggs cells work?<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p><strong>The eggs grow and mature inside the follicles<\/strong>. In the woman\u2019s ovaries\u00a0there are a large number of follicles, but each month only one will develop and lead to ovulation of a mature egg.<\/p>\n<p><strong>This mature egg will travel through one of the fallopian tubes<\/strong>, and if it is fertilised by a spermatozoid along the way it will develop into an embryo that can implant when it reaches the uterus, resulting in a pregnancy.<\/p>\n<p><strong>The\u00a0<a href=\"https:\/\/urecentrogutenberg.es\/en\/ovarian-stimulation-in-assisted-reproduction-we-answer-your-most-frequently-asked-questions\/\" target=\"_blank\" rel=\"noopener\">medication we administer to females in an IVF cycle<\/a>\u00a0stimulates the growth of several follicles.<\/strong>\u00a0The aim is to obtain a good number of eggs so that, in the laboratory,\u00a0<strong>we can obtain enough embryos and optimise treatment to the maximum<\/strong>.<\/p>\n<p>Follicle growth is monitored via ultrasound. When a follicle reaches 18 millimetres in size, the egg it contains should have completed the maturation process and should be suitable for the process of fertilisation. It is at this time that we can schedule the egg retrieval procedure in the laboratory.<\/p>\n<p>&nbsp;<\/p>\n<h2><span class=\"ez-toc-section\" id=\"How_we_classify_eggs_in_In_Vitro_Fertilisation\"><\/span>How we classify eggs in In Vitro Fertilisation<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><strong>The eggs obtained for\u00a0<a href=\"https:\/\/urecentrogutenberg.es\/en\/in-vitro-fertilisation\/\" target=\"_blank\" rel=\"noopener\">In Vitro Fertilisation<\/a>\u00a0must be mature enough to be fertilised by a spermatozoid.<\/strong>\u00a0This stage of maturity is called Metaphase II (MII), and means that the cell and its nucleus have undergone the number of divisions which are specific to and necessary for a gamete in order to obtain the correct genetic material before fertilisation.<\/p>\n<p>Metaphase II is characterised by the appearance of the first polar body (PB): a small spherical particle between the two membranes that surround the egg, and which contains half of the egg\u2019s chromosomes (the other half is still inside).<\/p>\n<p>Eggs that are still in a previous stage of maturity, Metaphase I (MI) or Germinal Vesicle (GV), cannot be fertilised by a spermatozoid. It is common that, during the process of ovarian stimulation for In Vitro Fertilisation, not all follicles will grow and mature at the same rate. For this reason it is possible to obtain immature eggs (MI or GV), which will not be of use in the laboratory.<\/p>\n<p>&nbsp;<\/p>\n<h2><span class=\"ez-toc-section\" id=\"What_does_an_egg_look_like_when_we_obtain_it_through_assisted_reproduction\"><\/span>What does an egg look like when we obtain it through assisted reproduction?<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>As we said before,\u00a0<strong>the egg is a large, spherical cell measuring about 130 microns in diameter<\/strong>. When we retrieve it from the follicle where it had been maturing,\u00a0<strong>it is surrounded by a group of small cells called the cumulus-corona complex<\/strong>. Its image would resemble that of a fried egg, where the yolk is the egg.<\/p>\n<p>This appearance means that, most of the time, the stage of maturity of the egg cannot be correctly observed. That is to say that we cannot see the presence of the polar body we mentioned before.<\/p>\n<p>&nbsp;<\/p>\n<h2><span class=\"ez-toc-section\" id=\"How_we_know_if_the_eggs_that_have_been_retrieved_are_mature\"><\/span>How we know if the eggs that have been retrieved are mature<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p><strong>The moment in which we can tell if the eggs collected during assisted reproduction treatment are mature is when we remove the cells that surround them<\/strong>. This process, called\u00a0<em>egg decumulation or denudation<\/em>, will allow us to confirm the presence of the polar body under the microscope.<\/p>\n<p>If an egg presents the polar body and a clear cytoplasm, we are looking at a metaphase II oocyte.<\/p>\n<p>If it does not present the polar body but we see a clear cytoplasm, we are looking at a metaphase I oocyte. If we can see an inner nucleus in the centre of the cytoplasm, we are looking at a germinal vesicle.<\/p>\n<p>In the event that insemination is carried out using sperm microinjection (<a href=\"https:\/\/urecentrogutenberg.es\/en\/in-vitro-fertilisation\/\" target=\"_blank\" rel=\"noopener\">ICSI<\/a>), it will be performed just a few hours after the oocytes were collected. Only MII eggs that present the first visible polar body will be microinjected.<\/p>\n<p>If, on the other hand, we are going to carry out traditional IVF, the mature egg will be observed 18 hours after it was inseminated, i.e. the day after it was obtained. The eggs that were correctly fertilised by a spermatozoid will have two polar bodies, as a correctly fertilised mature egg will extrude a second polar body.<\/p>\n<p>&nbsp;<\/p>\n<h4><span class=\"ez-toc-section\" id=\"Do_you_have_any_other_questions_about_assisted_reproduction\"><\/span>Do you have any other questions about assisted reproduction?<span class=\"ez-toc-section-end\"><\/span><\/h4>\n<p>Do not hesitate to contact us!\u00a0<strong>Our team of the\u00a0<a href=\"https:\/\/urecentrogutenberg.es\/en\/international-team\/\">international department<\/a>\u00a0will be happy to answer them and invite you to a first free consultation with us online<\/strong>\u00a0or in person to get to know us.<\/p>\n","protected":false},"excerpt":{"rendered":"<p>What is an egg cell? Eggs are sex cells, or the female gametes, which carry the genetic material a woman will pass on to her children.\u00a0At first glance, eggs are large, spherical cells that are produced\u00a0approximately every 28 days\u00a0in the female\u2019s ovary. And as you already know, eggs play a fundamental role in the early [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":34317,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[499,500],"tags":[511,512,504,572,573,507,508,502,520,513,576,567,503,509,510,575,574,515,505],"class_list":["post-39489","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-assisted-reproduction-treatments-and-techniques","category-laboratory-stuff","tag-assisted-reproduction-clinic-in-algeciras","tag-assisted-reproduction-clinic-in-malaga","tag-assisted-reproduction-techniques","tag-clinica-gutenbeg-en","tag-differences-between-mature-and-immature-eggs","tag-fertility-clinic-in-algeciras","tag-fertility-clinic-in-malaga","tag-fertility-treatments","tag-fertility-treatments-in-algeciras","tag-fertility-treatments-in-malaga","tag-germinal-vesicle","tag-gutenberg-malaga-en","tag-in-vitro-fertilisation","tag-ivf-clinic-in-algeciras","tag-ivf-clinic-in-malaga","tag-mature-eggs","tag-oocyte-metaphase-ii","tag-reproductive-treatments","tag-ure-centro-gutenberg-en"],"_links":{"self":[{"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/posts\/39489","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/comments?post=39489"}],"version-history":[{"count":1,"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/posts\/39489\/revisions"}],"predecessor-version":[{"id":39491,"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/posts\/39489\/revisions\/39491"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/media\/34317"}],"wp:attachment":[{"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/media?parent=39489"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/categories?post=39489"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/urecentrogutenberg.es\/en\/wp-json\/wp\/v2\/tags?post=39489"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}