Pregnancies

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Ectopic Pregnancies

  • Implantation in a non-uterine site occurs at a rate of about 0.25-1%
  • The ampulla of the uterine tube is the most common ectopic implantation site

In Vitro Fertilisation (IVF)

  • The process by which one or more eggs (oocytes) are fertilised outside the body. Fertilisation is either achieved by placing a droplet of washed sperm (∼50.000) onto each egg or if the sperm count is low a single sperm can be injected into each egg (Intra Cytoplasmic Sperm Injection – ICSI)
  • Embryos can be placed in to the uterus at the 6-8 cell stage (3-days culture) but some clinics culture the embryos for 5 or 6 days to ensure healthy blastocyst stage embryos are placed into the uterus
  • All cells in the early embryo (until about the 8-cell stage) are said to be totipotent. That means each cell is capable of forming a complete human
  • So couples using IVF can use genetic screening of their embryos by having a cell removed from their embryos and tested for its genotype. The embryo will still develop normally
  • More than 100 disease can be detected including hemophilia A, muscular dystrophy, Tay-Sachs disease, cystic fibrosis and Down syndrome

Stem Cell Research

  • Stem cells are unspecialized cells that can renew themselves for long periods through cell division. Under certain experimental conditions, they can be induced to become cells with special functions such as the beating  cells of the heart muscle or the insuline-producing cells of the pancreas
  • Human embryonic stem cells are obtained from the inner cell mass-the early embryo
  • In the USA it is forbiden to destroy a human embryo to obtain stemm cells. So they are not allowed to remove the inner cell mass in tutipotent cells. There is interest in posibility that at the 8-cell stage the cells are no longer tutipotent but are still pluripotent

Multiple Gestation

  • About 1:80 human births is a twin pregnancy
  • About 2/3 of twins are fraternal (Dizygotic) – derived from 2 eggs
  • About 1/3 of twins are identical twins (monozygotic)
  • 35% of mono zygotic twins divide between 2-8 cell stage, get two babies  with two amnion, two chorions and either one fused or two separateplacentas – can not tell difference between these twins and fraternal until genetic testing is done
  • 65% of monozygotic twins occur by divisionof the inner cell mass after first week.  At this point two embryos will develop with two amniotic sacs, one chorionic sac and a common placenta
  • IVF has greatly increased the number of fraternal (dizygotic) twins

Monozygotic Twins

  • Separation at the two blastomere stage can lead to twinning
  • Splitting of the inner cell mass is the most common cause of identical twins
  • Incomplete separation of the inner cell mass can lead to conjoined twins

 

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7 Responses to Pregnancies

  1. Rekha Sahay says:

    very informative post.
    Thanks for following my blog.

    Like

  2. -Eugenia says:

    Well written account. Thank you for sharing and thank you for following BrewNSpew.

    Like

  3. Twinkletoes says:

    I appreciate the knowledge you shared. Look forward to reading more of your work. Cheers!

    Liked by 2 people

  4. Swati Desai says:

    Thanks for sharing such a well researched topic.

    Like

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