A new life begins when a sperm with paternal genes fertilizes the egg with maternal genes. Normally, one would expect the paternal and maternal genes to peacefully cohabit till at least the baby is delivered. But no! The battle of the sexes starts right there and then in the womb. Looks like the battle between the sexes was always going to happen. These findings, according to scientists, could explain why the growth of some babies is retarded while in the womb. Let’s find out more!
The sexes battle over food
For the fetus to grow, it needs adequate nourishment. The nourishment for the fetus comes from the placenta, a special tissue made of both the baby’s and the mother’s cells. The placenta connects with the baby via the umbilical cord, which contains vessels that carry nourishment and waste substances to and from the baby, respectively.
The vessels in the placenta grow at remarkable rates and can reach lengths of up to about 320 kilometers. This underscores the length the body takes to safeguard pregnancy. However, sometimes these vessels don’t grow optimally and cause about 15% of babies to develop poorly in the womb. Contrarily, if the vessels are overgrown, they may constitute another problem as the baby tends to be overgrown.
In essence, to ensure the baby grows within normal limits, it has an inbuilt mechanism that signals the blood vessels to grow optimally. In efforts to study this signaling mechanism and how it affects the growth of placental vessels, scientists at Cambridge used genetically engineered mice.
One of the authors, Dr. Ionel Sandovici, said, “As it grows in the womb, the fetus needs food from its mom, and healthy blood vessels in the placenta are essential to help it get the correct amount of nutrients it needs… We’ve identified one way that the fetus uses to communicate with the placenta to prompt the correct expansion of these blood vessels. When this communication breaks down, the blood vessels don’t develop properly, and the baby will struggle to get all the food it needs.”
According to the researchers, the signal is insulin growth factor 2[IGF2]. As the name implies, it has a lot to do with growth. But watch out! Too much as well as too little is bad for the baby. The fetus sends IGF2 that reaches the placenta through the umbilical cord.
Dr. Sandovici added: “We’ve shown that IGF2 also acts as a classical hormone–it’s produced by the fetus, goes into the fetal blood, through the umbilical cord, and to the placenta, where it acts.”
The study further revealed that paternal genes try to increase the nutrients by increasing the growth of blood vessels, which increases blood supply to the fetus. Maternal genes, on the other hand, counteract this action by reducing the growth of blood vessels
This discovery made, lead author Dr. Miguel Constância, described the paternal gene as ‘greedy and selfish’ and the maternal gene as ‘ countermeasures to balance these demands’
Clinical significance
The battle of the sexes from the womb can expand our knowledge on the interaction of the fetus, the placenta, and the mother. Furthermore, the information we could uncover could offer us ways to ensure that babies’ growth in the womb is hitch-free.
Final thoughts
The time babies spend in the womb is perhaps the most important phase of life, and one of the most important factors is nutrition. Several genes regulate the flow of nutrients, and it’s important we study these genes to improve pregnancy outcomes.
References
Sandovici, I., Georgopoulou, A., Pérez-García, V., Hufnagel, A., López-Tello, J., Lam, B. Y. H., Schiefer, S. N., Gaudreau, C., Santos, F., Hoelle, K., Yeo, G. S. H., Burling, K., Reiterer, M., Fowden, A. L., Burton, G. J., Branco, C. M., Sferruzzi-Perri, A. N., & Constância, M. (2022). The imprinted Igf2-Igf2r axis is critical for matching placental microvasculature expansion to fetal growth. Developmental Cell, 57(1), 63–79.e8. https://doi.org/10.1016/j.devcel.2021.12.005
