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  "path": "/news/2026-04-human-pregnancies-singletons.html",
  "publishedAt": "2026-04-23T17:20:09.000Z",
  "site": "https://medicalxpress.com",
  "textContent": "Each month during a woman's menstrual cycle, an ovary prepares 10–20 antral follicles, fluid-filled sacs that hold immature eggs, for maturation. In most cycles, only one follicle is selected to undergo maturation, eventually releasing an egg ready for fertilization. In fact, only 2–3% of natural pregnancies result in fraternal twins, or two eggs being released and fertilized. For natural pregnancies, it is most common for only one egg to be released and fertilized.",
  "title": "Selection model helps explain why most human pregnancies are singletons"
}