Why Can a Woman Not Get Pregnanat Again When She Is Pregnant
Can a adult female get pregnant when she is already pregnant? In other words, can she have 2 foetuses in her uterus at unlike stages of development?
The technical term for this is superfetation. In humans, information technology's possible, simply it's very uncommon.
Two g years agone, that corking Greek thinker Aristotle wondered virtually this very topic, specifically every bit regards the hare.
Aristotle noticed that when a hare gave birth, quite often the offspring in a single litter would fall into ii distinct classes: in that location would exist a agglomeration of full-sized robust baby hares, and another bunch of scrawny frail infant hares.
It was, he thought, equally though the mother hare had become pregnant and so — while pregnant — had conceived a second fourth dimension.
There was goose egg fundamentally incorrect with the smaller, weedy offspring, Aristotle idea, autonomously from the fact that they had not spent enough time growing in their mother's uterus. And he was correct.
Why is it so rare?
Unremarkably in humans, there are iii separate barriers to finish a female from getting pregnant once more if she is already meaning.
The first barrier is the hormonal changes after conception that cease the ovaries from releasing some other egg.
The second barrier is physical: a mucous plug. About immediately subsequently formulation, a plug forms in the cervix and sits at the peak of the vagina. This plug stops whatever other sperm from inbound the uterus and getting to a second egg.
Third, there are physical and chemical changes that happen to the inner lining of the uterus in pregnancy. These changes usually stop a second fertilised egg from being able to attach to the uterine wall.
All the same, some brute species manage to get around all these barriers. About 1 to 2 per cent of all meaning cows testify signs of beingness potentially fertile while they are already pregnant, and superfetation has been observed in animals such every bit the mouse, the rabbit, the sheep, the buffalo, the mink, and the Australian swamp wallaby.
Could superfetation happen to me?
Superfetation is extremely uncommon in humans, with fewer than a dozen cases in the medical literature.
A typical example is that of Julia Grovenburg, a 31-year-sometime woman from Arkansas.
Ms Grovenburg and her partner had been trying to get meaning for three years, and had begun to consider adoption of a child.
Only amazingly she conceived twice in 2009 — a few weeks apart. The Daily Post claimed that, in a "drastic and final attempt to have children of their own", the couple had given it one terminal try.
This is a curious utilize of the discussion desperate.
I might be quondam-fashioned, but it seems odd to me to regard sexual intercourse as "a desperate and final attempt" to get pregnant.
Information technology makes y'all wonder what measures they tried before they got desperate.
Anyhow, Ms Grovenburg was pregnant — merely then things went odd: the ultrasound showed two contained babies, each living in their own divide amniotic sac. But one was much larger and more developed than the other.
As the ultrasounds scans mounted up for Ms Grovenburg, both foetuses seemed to be growing unremarkably and healthily, though it appeared equally if i foetus had simply started a few weeks afterwards the other.
In other words, Mrs Grovenburg had conceived a 2nd infant a few weeks after becoming significant with the first.
No manner to prove it
Now we don't accept rock-solid proof that this is what happened. Nosotros would demand a series of ultrasound scans to evidence that.
These scans would need to document a series of changes — starting with no foetus or amniotic sac in the uterus, so a single foetus in its single amniotic sac, and a 2d foetus appearing in their own second amniotic sac after a few weeks.
People don't unremarkably get a series of ultrasound scans immediately after sexual intercourse, and so this kind of hard information is difficult to go.
Just there is some evolutionary biology backside superfetation. Female European brownish hares frequently have a second pregnancy while already meaning. This means females can take about one tertiary more offspring in each breeding flavor.
For humans, more than babies each breeding cycle isn't always a plus — specially if you're trying to get a good night's sleep.
Posted , updated
Source: https://www.abc.net.au/news/science/2017-04-11/dr-karl-superfetation-can-you-get-pregnant-during-pregnancy/8430238
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