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Twins or not?

  1. Yes

    1 vote(s)
    7.7%
  2. No

    12 vote(s)
    92.3%
  1. Nov 28, 2007 #1
    If two human siblings were born within 365 days of each other then they must be twins (i.e. born on the same date)?

    Please explain.
     
  2. jcsd
  3. Nov 28, 2007 #2

    J77

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    :confused:

    I would assume it not possible to get pregnant whilst pregnant...

    However, more sprogs are easily conceived after the first one pops out, after 9 months.

    Therefore, not twins.

    Unless this is a riddle...
     
  4. Nov 28, 2007 #3

    jim mcnamara

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    gestation period for humans is ~275-280 days - meaning a mother could have one baby born in January, conceive in February and give birth in November. Two non-twin kids form one mother in less than 365 days - per the wording of your question.

    Now if you asked, "can a mother conceive twice and give birth normally twice (to two or more children) in one year" - the answer is no. They would have to be multiple births because 275 * 2 > 365
     
  5. Nov 28, 2007 #4

    Moonbear

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    Not all that easily. It takes some time for ovulations to resume after one gives birth, though that time varies among individuals and whether or not one is breast feeding. But, still possible to have a baby born in January and another in December (especially if the second is a bit premature).

    I'm also confused by the point of the question. Pivoxa, could you explain the reasining behind your question? Why would you think they're twins? Twins means they are conceived at the same time.
     
  6. Nov 28, 2007 #5
    The question may seem odd. Another way to ask it is:

    Is it possible for two sibilings to be born within the same year but are not twins? So one baby at a time in mother's tummy but born within the same year although none born prematurely.
     
  7. Nov 28, 2007 #6

    Astronuc

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    Yes - but it it not common. The first child could be born in Jan, and then the second conceived in late March or early April and then born in Dec. Obvoiusly, as Jim indicated, the first child would be conceived during the previous year. It is not possible to conceive, deliver and then conceive and deliver, in the same year, and not have premature children.

    Usually however, a woman who breastfeeds delays subsequent ovulation, while breastfeeding.

    I have one brother 14 months younger than me, so my parents go busy soon after I was born.
     
    Last edited: Nov 28, 2007
  8. Nov 28, 2007 #7

    DaveC426913

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    Well this is my wife's field of expertise. If you could be more specific I might be able to give you details.
     
  9. Nov 28, 2007 #8
    What do you mean by conceived? The important thing is that the siblings are born (out of mother's stomach) in the same year but none born prematurely.
     
  10. Nov 29, 2007 #9

    Moonbear

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    Conception refers to fertilization...the time when intercourse actually occurred that the pregnancy was initiated. And, just for accuracy, since this is a science forum, embryos/fetuses develop within the uterus, not the stomach. If you wish to refer more generally to the area of the body rather than to internal organs, abdomen is an acceptable term.

    So, yes, if you are referring to birth only, and not the entire pregnancy, then it is possible for two siblings to be born within the same year, although very uncommon for the reasons already discussed above.
     
  11. Nov 29, 2007 #10

    J77

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    I must have some unusual friends then :smile: -- either that or they like the idea of maternity leave too much after the first has arrived :biggrin:

    (My gf is also less than a year older than her younger sister.)
     
  12. Nov 29, 2007 #11
    I raised the question because I know two sibilings in the same year level which dosen't look alike enough to be twins.

    So that is a chance that they were born at different times of the year.
     
  13. Nov 29, 2007 #12

    DaveC426913

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    Ah.

    Well, just because they're born at the same time doesn't mean they're identical twins. Certainly in this day and age of superovulation technology, it is quite possible that they are due to the simultaneous fertilization of two different ova (as opposed to the splitting of a single ovum after fertilization). That would make them no more twins than any other pair of siblings.

    BTW, it is also possible (and has happened) that "twins" do not even share the same father.
     
  14. Nov 29, 2007 #13
    Offcourse, the stomach is for food processing.:)
     
  15. Nov 29, 2007 #14
    Twins without the same father? That must be freaky as in low probability.

    The sibilings I had in mind look alike enough to be sisters but not any kind of twin.
     
  16. Nov 29, 2007 #15

    brewnog

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    It only requires sperm from two separate men to be around two ova at a similar time. The low probability of it happening is largely because most women trying to get pregnant stick with one partner whilst doing it.

    Someone correct me if I'm wrong, but non-identical twins don't typically look any more alike than any other siblings. An ex girlfriend of mine looked little like her (non-identical) twin sister, and my current girlfriend's twin is a boy...
     
    Last edited: Nov 29, 2007
  17. Nov 29, 2007 #16
    Most fraternal (not sure if thats spelled right) twins do look similar. Mary-Kate and Ashly Olsen aren't identical twins, and they look it. (I didnt really want to use them as an example, but they are widely know).

    But that can seriously happen?? Twins from different fathers!?!
     
  18. Nov 29, 2007 #17

    nrqed

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    But they may simply be heterozygote twins! (i.e. two different embryos were fertilized at the same time). So they are born at the sam etime but don't have the same genetics. two heterozygote twins may even be of different sex!
     
  19. Nov 29, 2007 #18

    Moonbear

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    Precisely. Fraternal twins would not share any more genetics than any other sibling pair, so can range from very similar in appearance to very different, the same way some siblings look very similar and others quite different.
     
  20. Nov 29, 2007 #19

    DaveC426913

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    The other thing that is common these days is embryo transplant. Which means, again, no more similarity than siblings. In fact, they are simply sibs that are artificially brought to term simultaneously.

    How old is the mom? More than, say, 35 years older than the kids?
     
  21. Nov 29, 2007 #20

    Danger

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    It's been so long (+/- 40 years) that I honestly can't remember whether I met them or only read about them, but there were a couple of girls who were born as twins with 2 different fathers. I don't know whether it was the result of a three-way or just a couple of different partners very close together chronologically. Unfortunately, my sex education is of the back-alley variety, so I'm not too sure about the medical aspects of that situation.
     
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