If a woman is already pregnant and becomes pregnant again, then this condition is called superfetation. Superfetation occurs when a second pregnancy occurs during an existing pregnancy. This occurs when a second egg occurs a few days or weeks after the first egg has been fertilized and implanted in the uterus. Superfetation is extremely rare in humans. This has been confirmed in only a few cases in medical history. For example, such things are common in other animals like fish, rabbit and badger.
Why does superfetation occur?
Children born from superfetation are not twins. Rather, there are two separate pregnancies. They may be born on the same day during the same birth. And they are often considered twins. Doctors have not yet been able to figure out why superfetation occurs because ovulation occurs very rarely during pregnancy. Superfetation should not be confused with superfecundation. Which occurs when two eggs released during the same cycle are fertilized at different times by two different fathers.
Progesterone levels are high during pregnancy
When you get pregnant, you have to ovulate and pregnancy hormones work against this. Progesterone levels are very high during pregnancy. Prevents your body from releasing another egg. Even if you ovulate and another egg is released, sperm must fuse with that egg. The thick cervical mucus formed during pregnancy prevents sperm from passing through. The fused egg needs to be transplanted into the lining of the uterus. Which is almost impossible due to the hormonal changes of the already established pregnancy.
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Although superfetation is relatively rare in humans, it may be common in other animals. Which includes rodents, rabbits, horses, sheep, kangaroos, cats and some species of fish. Superfetation in these animals may actually be a reproductive strategy to increase the chances of producing more children. If you are pregnant and your first trimester ultrasound shows two growing fetuses of approximately the same age and size. So chances are you will have twins and any future difference in the size of the two babies will be due to developmental anomalies and not different days of conception.
Disclaimer: Some of the information given in the news is based on media reports. Before implementing any suggestion, you must consult the concerned expert.
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