Yes, the human body can release an egg from both ovaries during the same reproductive cycle. While the release of a single egg (monovulation) is the typical biological pattern, a dual release is a known natural phenomenon. This process, often called hyperovulation or multiple ovulation, involves two separate mature eggs being made available for fertilization. This dual occurrence happens within a short window, making the eggs available for fertilization at the same time within the cycle.
How the Body Selects a Single Egg
The standard monthly cycle involves a hormonal cascade designed to select only one egg for release. This process begins when the pituitary gland releases Follicle-Stimulating Hormone (FSH), stimulating ovarian follicles to begin growing and maturing. As the follicles grow, they produce estrogen, and eventually, one becomes the “dominant follicle,” producing increasingly high levels of estrogen.
The rising estrogen levels trigger a negative feedback loop, reducing the secretion of FSH. With lower FSH, the smaller follicles stop growing and naturally degenerate. Only the dominant follicle, which is less reliant on FSH, continues to mature. The final stage is a surge of Luteinizing Hormone (LH), which prompts the dominant follicle to rupture and release its single egg.
Mechanisms of Dual Egg Release
The natural mechanism for single egg selection is occasionally overridden, allowing two eggs to reach maturity simultaneously. This dual maturation occurs when the suppressive effect of the dominant follicle’s hormones is bypassed or incomplete. Hyperovulation can result in both eggs coming from the same ovary or, more commonly, one egg being released from each ovary.
One natural cause of hyperovulation is a genetic predisposition resulting in higher-than-average levels of FSH. If a person secretes more FSH or has follicles more sensitive to the hormone, two follicles may reach the dominant stage together. This genetic link explains why a family history of fraternal twins often increases the likelihood of hyperovulation.
A second common mechanism involves fertility treatments, which are designed to stimulate the ovaries to produce multiple eggs. Medications like clomiphene citrate or injectable gonadotropins increase the level of FSH or its effect on the ovaries. This intervention intentionally overrides the body’s natural single-selection process to increase the chances of pregnancy.
The Outcome: Fraternal Twins
The biological consequence of two eggs being released during one cycle is the possibility of conceiving fraternal twins. Fraternal twins (dizygotic twins) result when two separate eggs are fertilized by two separate sperm. Since they originate from two distinct fertilization events, these twins are genetically unique, sharing about 50 percent of their DNA, similar to non-twin siblings.
This process is fundamentally different from the formation of identical twins (monozygotic), which occur when a single fertilized egg splits into two embryos early in development. The ability of both ovaries to release an egg at the same time is the required biological precursor for the conception of natural fraternal twins.