I have also heard that IVF and other non-intercourse related methods can do this. IE you can ask the IVF clinic to split the eggs before insertion?

How soon do you know from a natural birth too? Can one increase their chance? Certain foods?

  • This doesn't warrant a new answer (the existing one is very good), but to answer one of your questions that isn't addressed - twins are usually detected during an ultrasound starting from as early as 5 weeks. At that point, there will be two or more gestational sacs visible. If they are both viable, from week 6 onward, two or more embryos are visible.
    – YviDe
    Commented Oct 18, 2015 at 13:53
  • +0. As Susan said, that twins and triplets more likely to miscarry or die young. Also, caring for twin or triplet newborns is enormously stressful. Why would you want to cause this stress to you and your wife? Also, was this her idea, or yours? Commented Apr 24, 2017 at 19:18

1 Answer 1


First of all, just to be clear: IVF-associated twinning and “tripletting” are most commonly of the dizygotic (“fraternal”) variety. You appear to be asking about monozygotic (“identical”) twinning given the reference to “splitting the egg.” I will provide a brief overview of both.

Types of multiple conceptions and relationship to IVF

Dizygotic ("fraternal") twins (and higher multiples) occur because more than one egg is fertilized. This is very common during the in vitro process because the ovaries are stimulated using medications, as opposed to the normal menstrual cycle where usually only one egg is release. Because multiple birth pregnancies have considerably higher rates of both maternal and fetal complications,1 IVF centers and mothers together have to make a decision weighing the risk of multiple embryo transfer with the benefits of improved probability of successful live birth. In some countries, there are laws against transferring more than one embryo, but in the United States this varies by center, and overall about 35 percent of IVF pregnancies are twins, with 7-8 % being triplets.2

Monozygotic ("identical") twins occur because an early embryo divides after fertilization. This results in two embryos with identical DNA (hence the terminology and phenotype - “identical”). These have also been shown to be more common in IVF pregnancies, although the degree of over-representation is considerably less marked compared to the situation with dizygotes. The mechanism is also less clear.

Is this desirable?
Monozygotic twins (and higher multiples) have markedly increased rates of every pattern of fetal and perinatal mortality, overall between four and seven times the rate compared to singletons.3 This may be in part due to the fact that the process of splitting is itself a “deformity” of sorts that tends to cluster with other deformities. It is also the case that monozygotic multiple births at times share, to varies degrees, portions of the placental sac (mono-chorionic and at times also mono-amniotic). Mono-amniotic are susceptible to umbilical cord entanglement, which can lead to serious complications. Those that do not share an amniotic sac (mono-chorionic, di-amniotic) are susceptible to something called Twin-twin Transfusion Syndrome wherein blood is shunted from one twin to the other via vascular connections between the placentas. This can lead to severe anemia of the “donor” twin and polycythemia (overload of red blood cells) in the “recipient”, both of which carry complications.3

You asked:

can (we) ask the IVF clinic to split the eggs before insertion?

Your goal appears to to increase the chance of monozygotic twinning. Although it has been shown3 that certain factors do increase this chance (advanced maternal age and some technical considerations during the fertilization step), because of the above considerations about complications during monozygotic multiple embryo pregnancies, this is considered an undesirable outcome during IVF. As such, IVF centers are unlikely to do anything likely to increase this chance.

  1. Seoud MA, Toner JP, Kruithoff C, Muasher SJ. Outcome of twin, triplet, and quadruplet in vitro fertilization pregnancies: the Norfolk experience. Fertil Steril. 1992 Apr;57(4):825-34.

  2. http://www.yalescientific.org/2012/05/the-more-the-merrier-limiting-the-number-of-embryo-implantations/

  3. Abusheikha N, Salha O, Sharma V, Brinsden P. Hum Reprod Update. Monozygotic twinning and IVF/ICSI treatment: a report of 11 cases and review of literature. 2000 Jul-Aug;6(4):396-403.

  • +0. The questioner asked a question in lay terms, but you gave an answer full of medical jargon. Your answer is useful to medical experts, but may not be as useful to the asker. In the future, it would be best if you could please try to avoid jargon as much as possible, especially when the asker is a layperson. Commented Apr 24, 2017 at 19:10
  • Thanks @tealhill, I'd be happy to try to improve it. I attempted to define my terms in ways that would be comprehensible to OP and others. What jargon is used here that isn't defined?
    – Susan
    Commented Apr 24, 2017 at 19:23
  • 1
    +1 Respectfully, I disagree with the previous commenter. Your terms are well defined, and anyone who is actually embarking on IVF really needs to be able to understand this level of technical terminology. I am not in the medical profession, and I found it all very helpful. The only change that I might recommend would be to repeat the common names ("identical" and "fraternal") in parentheses after the formal names in the paragraphs where you define them. (e.g. **Dizygotic (fraternal) twins and higher multiples occur because more than one egg.....") As you did in paragraph 1.
    – Adam
    Commented Aug 15, 2017 at 20:06
  • Thanks, @Adam, revised accordingly. Just FYI, you can always propose an edit if you have a specific suggestion. This was easy enough, though, so no problem.
    – Susan
    Commented Aug 15, 2017 at 20:10

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