In the course of fertilization, when two sperms fertilize two mature ova due to multiple ovulation under the control of hypothalamo-pituitary-ovarian axis promoted by different physiological, genetic, and other environmental factors, including the use of advanced reproductive technologies to maximize reproductive success.
The word “twins” originates from old English: “twi” means two or “twin” means double. Twin babies are although less frequent but not rare in parallel with the single child. Dizygotic (DZ) or fraternal twins are produced from two different ova fertilized by two different sperms whereas monozygotic (MZ) or identical twins derive from a single ova dividing into two separate embryos. Conjoint twins are also identical but not separated. Compare to the prevalence of monozygotic twins which is almost constant, the prevalence of dizygotic twins varies over time across the different places in the world. In...
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