Nourishment of embryo during first 11 weeks of pregnancy
After fertilisation, the fertilised egg travels down the fallopian tube to the uterus. After about 9 days of fertilisation it is implanted into the uterine lining, the endometrium. In the first trimester, particularly in the first 11 weeks of pregnancy, all the nourishment for the growth of a baby are supplied by secretions from glands in the uterus lining, termed as “womb-milk”.
Endometrium behaves very differently compared to normal in pregnancy. The endometrial glands start storing large amounts of glucose as glycogen, which is then secreted to nourish the embryo during its first 11 weeks. However after this time, the nourishment is taken over by mother’s blood supply delivered via umbilical cord and ultimately the “womb-milk” is dried up. But how the building blocks were transported to the embryo and placenta was a mystery until now.
For the first time, the researchers from the University of Manchester, UK, have worked out in detail the mechanism of the transport of nutrients from these glands into the developing embryo.
To investigate, the team examined womb, placenta and embryonic tissue donated by women who terminated their pregnancies. The samples collected at all stages of early pregnancy, helped them to analyse how the endometrium changed over time. They used a staining dye to see the localisation of glycogen in tissues. The glycogen was abundant in the recesses of the womb lining, where it was broken down into smaller molecules. These molecules then diffused and stored into a cavity just outside the placenta, the intervillous space. Some of the sugar stored temporarily in the intervillous space were used for energy generation for the growth of the embryo, and the rest is reconverted to glycogen and then absorbed by the placenta. They also tracked the transport of glycoproteins (containing sugar fragments and protein, that can be broken down into amino acids: the building blocks of tissue), a very crucial growth factor.
Next, the team plans to investigate how a mother’s diet and other external factors, like smoking, affect the build-up of glycogen in the endomemtrium.
Experts say that the first few weeks of pregnancy is a critical phase for embryonic development and thus this novel study adds new insights into the enzymes associated with delivery of glucose across cell membranes to the embryo and placenta.
Journal reference: Placenta, DOI: 10.1016/j.placenta.2015.01.002
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