Male pregnancy

thumb|Pregnant male seahorse, October 2006

Male pregnancy is the incubation of one or more embryos or fetuses by organisms of the male sex in some species. Most species that reproduce by sexual reproduction are heterogamous—females producing larger gametes (ova) and males producing smaller gametes (sperm). In nearly all animal species that give live birth, offspring are carried by the female until birth, but in fish of the family Syngnathidae (pipefish, seahorses and the leafy seadragon), males perform that function.

In animals

Syngnathidae family

thumb|Pregnant male seahorse, 2006

The fish family Syngnathidae has the unique characteristic of a highly derived form of male brood care referred to as "male pregnancy". The family is highly diverse, containing around 300 different species of fish. Included in Syngnathidae are seahorses, the pipefish, and the weedy and leafy seadragons. The males of some of these species possess a brood pouch on the trunk or tail; in other species, the eggs are merely attached to the male's trunk or tail when the female lays them. Although biologists' definitions of pregnancy somewhat differ, all members of the family are considered by ichthyologists to display male pregnancy, even those without an external brood pouch.

Fertilization may take place in the pouch or in the water before implantation, but in either case, syngnathids' male pregnancy ensures them complete confidence of paternity. After implantation in or on the brood pouch or brood patch, the male incubates the eggs. Many species osmoregulate the brood pouch fluid to maintain a suitable pH level for the developing embryos. In at least some species, the male also provisions his offspring with nutrients such as glucose and amino acids through the highly vascularized attachment sites in or on his body.

This period of incubation can take much longer than the production of another clutch of eggs by the female, especially in temperate regions where pregnancies last longer, leading to a reproductive environment in which sexual selection can be stronger on females than on males due to increased male parental investment. This reversal of usual sex roles has only been found in pipefishes, whereas seahorses have largely been accepted as monogamous. Some pipefish species display classical polyandry because of this unique situation. Male syngnathids usually prefer females with large body size and prominent ornaments such as blue skin pigmentation or skin folds. Syngnathid males in some species are apparently capable of absorbing eggs or embryos while in the brood pouch. In these cases, embryos with the highest survival rate are those whose mothers display the preferred phenotype.

Syngnathidae is the only family in the animal kingdom to which the term "male pregnancy" has been applied. The study attracted much attention and controversy, with some researchers questioning the utility of such research, and others raising questions of bioethics issues.

In 2023, Japanese scientists used skin cells from 2 male mice to create eggs and fathered a litter of seven babies.

In humans

Ectopic implant

Mammalian males, including humans, do not possess a uterus to gestate offspring.

Robert Winston, a pioneer of in-vitro fertilization, told London's Sunday Times that "male pregnancy would certainly be possible" by having an embryo implanted in a man's abdomen – with the placenta attached to an internal organ such as the bowel – and later delivered surgically. Ectopic implantation of the embryo along the abdominal wall, and resulting placenta growth would, however, be very dangerous and potentially fatal for the host, and is therefore unlikely to be studied in humans. Gillian Lockwood, medical director of Midland Fertility Services, a British fertility clinic, noted that the abdomen has not evolved to separate from the placenta during delivery, hence the danger of an ectopic pregnancy. Bioethicist Glenn McGee said "the question is not 'Can a man do it?'. It's 'If a man does have a successful [ectopic] pregnancy, can he survive it? Afterward, an in vitro fertilisation (IVF) procedure would be followed to insert the embryo into the male's transplanted womb.

In 1931, Lili Elbe, a trans woman, underwent a uterus transplant in an attempt to achieve pregnancy, but died of complications following the procedure.

Pregnancy in transgender men

thumb|300x300px|Pregnant trans man Zack Elías and his transgender wife, [[Diane Rodríguez, 2021]]

Some transgender men choose to become pregnant or wish to preserve their fertility. Those with functioning ovaries and a uterus can become pregnant. Masculinizing hormone therapy reduces fertility and stops the menstrual cycle, but is not considered an effective contraceptive—trans men taking testosterone may still become pregnant even if their periods have stopped. Trans men who undergo some masculinizing surgeries, including hysterectomy (removal of the uterus) and bilateral salpingo-oopherectomy (removal of both ovaries) are infertile.

In popular culture

Religious texts

Hindu religious texts, such as the Mahabharata (composition range from 300 BCE to 400 CE) and the Vishnu Purana (composition range from 400 BCE to 900 CE), contain the story of King Yuvanashva, who accidentally becomes pregnant by drinking a sacred potion intended for his queens. He proceeds with the pregnancy and his son, Mandhata, goes on to become a king renowned for his greatness, benevolence, and generosity.

In ancient Greek religion and myth, a version of Dionysus' birth (known in mainland Greece after 500 BCE, popularized in 500 CE), claims that Dionysus was sewn into Zeus’ thigh. "So the rounded thigh in labour became female, and the boy too soon born was brought forth, but not in a mother's way, having passed from a mother's womb to a father's." Athena was believed to have been born from the forehead of her father Zeus. The earliest mention is in Book V of the Iliad (c. 800 BCE), when Ares accuses Zeus of being biased in favor of Athena because "autos egeinao" (literally "you fathered her", but probably intended as "you gave birth to her").

Virgil Wong, a performance artist, created a hoax site featuring a fictitious male pregnancy, claiming to detail the pregnancy of his friend Lee Mingwei.

Male pregnancy as a trope in fan fiction―called mpreg―is also commonly explored in hentai, the subgenre of speculative erotic fiction known as the Omegaverse, and slash (homosexual) fan fiction, usually based upon fantasy series such as Supernatural, Harry Potter, and video game series such as Sonic the Hedgehog.

In 2021, Unicode approved the "pregnant man" and "pregnant person" emojis in version 14.0, and added to Emoji 14.0. However, this came with some controversy, as some viewed it to be "absurd".

References