Ectopic Pregnancy – Week 1 of Embryogenesis

by John McLachlan, PhD

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    00:01 Now, I mentioned ectopic pregnancy.

    00:03 As we’ll see in another lecture, fertilization takes place actually, quite near the ovary; the egg is shed from the ovary near the mouth of the oviduct shown in pink here.

    00:17 And the sperm has to swim all the way through the vagina up through the uterus and then along the oviduct in order to reach the egg, and fertilization takes place at this end of the oviduct. Then the fertilized egg begins to get wafted back down the oviduct towards the uterus. Normally, as we’ve seen, it will implant in the walls of the uterus.

    00:44 And the function of the zona pellucida among others is to stop implantation taking place too early. These outer cells of the syncytiotrophoblast are actually very aggressive and they will invade tissue with enormous enthusiasm. Normally, they have to be safely in the uterus where the walls are thick and ready to receive it to avoid the risk of causing any damage.

    01:13 If hatching takes place prematurely, or if the embryo is delayed in this process down the oviduct in any way, then there’s the risk that it might implant in the wrong place.

    01:24 The most common place for it to implant is actually in the oviduct itself. So you have a tubal ectopic pregnancy. The percentages shown in the diagram indicate where the most common kinds of ectopic pregnancy may actually be. Now, this process of implanting in the wrong place, this ectopic pregnancy can occur in as many as 1% of all pregnancies and therefore, it’s a relatively common event and one which is serious and potentially life-threatening.

    01:58 If it was undetected and the developing pre-embryo reached a major blood vessel, then that rupture could lead to the mother bleeding to death. So if you are thinking of studying medicine, it is the kind of thing that you would need to be very alert and aware of. So, what might we look for? Well, what would normally happen is that there would be some abdominal pain associated with the process, and also perhaps, some vaginal bleeding. In addition, there might be referred pain. Now, referred pain is an unusual phenomenon which you might not be familiar with. But the idea is that your insides are actually not very well supplied with sensitive nerves. And pain, something going wrong within that, might be referred by the nervous system to some other part of the body, for instance, the tip of the shoulder.

    02:53 So if a mother presented with some vaginal bleeding and pain in the tip of the shoulder, one of the things that you might want to think about is the possibility of an ectopic pregnancy.

    03:05 Under those circumstances, what you might want to do is to carry out a pregnancy test to check if she’s in the early stages of pregnancy because, of course, at this stage, she wouldn’t probably know that she’s pregnant at all. And perhaps an ultrasound scans to see if you can identify where the pre-embryo is actually implanted.

    03:25 There are some things which can actually predispose towards an ectopic pregnancy. So for instance, if mothers had a previous ectopic pregnancy, it suggests that there might be an issue perhaps in transport of the fertilized egg down the oviduct towards the uterus or if you suffered from pelvic inflammatory disease, this might also be a risk factor for an ectopic pregnancy.

    03:54 Very unusually, astonishingly, sometimes, ectopic pregnancies will continue as normal.

    04:00 It might have implanted in the tube, as we have described as the most common version, or it might even have fallen out the oviduct altogether and be lodged somewhere in the abdominal cavity in the abdominal linings. In pregnancy, if it doesn’t kill the mother at these early stages, if it progresses, there is a very small possibility that the baby might go towards a stage where it was old enough to be actually delivered.

    04:29 Of course, it would have to be delivered by caesarean section. It could not be born normally because it’s not in the uterus at all.

    About the Lecture

    The lecture Ectopic Pregnancy – Week 1 of Embryogenesis by John McLachlan, PhD is from the course Embryology: Early Stages with John McLachlan.

    Author of lecture Ectopic Pregnancy – Week 1 of Embryogenesis

     John McLachlan, PhD

    John McLachlan, PhD

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