Birth
Birth is the act or process of bearing or bringing forth offspring,[1] also referred to in technical contexts as parturition. In mammals, the process is initiated by hormones which cause the muscular walls of the uterus to contract, expelling the fetus at a developmental stage when it is ready to feed and breathe.
In some species, the offspring is
In marsupials, the fetus is born at a very immature stage after a short gestation and develops further in its mother's womb pouch.
It is not only mammals that give birth. Some reptiles, amphibians, fish and invertebrates carry their developing young inside them. Some of these are ovoviviparous, with the eggs being hatched inside the mother's body, and others are viviparous, with the embryo developing inside their body, as in the case of mammals.
Human childbirth
Humans usually produce a single offspring at a time. The mother's body is prepared for birth by
Enormous changes take place in the newborn's circulation to enable
Mammals
Large mammals, such as primates, cattle, horses, some antelopes, giraffes, hippopotamuses, rhinoceroses, elephants, seals, whales, dolphins, and porpoises, generally are pregnant with one offspring at a time, although they may have twin or multiple births on occasion.
In these large animals, the birth process is similar to that of a human, though in most the offspring is
In the case of whales, dolphins and porpoises, the single calf is normally born tail first which minimizes the risk of drowning.[7] The mother encourages the newborn calf to rise to the surface of the water to breathe.[8]
Most smaller mammals have multiple births, producing litters of young which may number twelve or more. In these animals, each fetus is surrounded by its own amniotic sac and has a separate placenta. This separates from the wall of the uterus during labor and the fetus works its way towards the birth canal.[citation needed]
Large mammals which give birth to twins is much more rare, but it does occur occasionally even for mammals as large as elephants. In April 2018, approximately 8-month old elephant twins were sighted joining their mother's herd in the Tarangire National Park of Tanzania, estimated to have been born in August 2017.[9]
Cattle
Birthing in
Dogs
Birth is termed whelping in dogs.[12] Among dogs, as whelping approaches, contractions become more frequent. Labour in the bitch can be divided into 3 stages. The first stage is when the cervix dilates, causing discomfort and restlessness in the dog. Common signs of this stage are panting, fasting, and/or vomiting. This may last up to 12 hours.[12] Stage two is the passage of the offspring.[12] The amniotic sac looking like a glistening grey balloon, with a puppy inside, is propelled through the vulva. After further contractions, the sac is expelled and the bitch breaks the membranes, releasing clear fluid and exposing the puppy. The mother chews at the umbilical cord and licks the puppy vigorously, which stimulates it to breathe. If the puppy has not taken its first breath within about six minutes, it is likely to die. Further puppies follow in a similar way one by one usually with less straining than the first usually at 15-60-minute intervals. If a pup has not been passed in 2 hours a veterinarian should be contacted.[12] Stage three is the passing of the placentas. This often occurs in conjunction with stage two with the passing of each offspring.[12] The mother will then usually eat the afterbirth.[13] This is an adaption to keep the den clean and prevent its detection by predators.[12]
Marsupials
An infant marsupial is born in a very immature state.[14] The gestation period is usually shorter than the intervals between oestrus periods. The first sign that a birth is imminent is the mother cleaning out her pouch. When it is born, the infant is pink, blind, furless and a few centimetres long. It has nostrils in order to breathe and forelegs to cling onto its mother's hairs but its hind legs are undeveloped. It crawls through its mother's fur and makes its way into the pouch. Here it fixes onto a teat which swells inside its mouth. It stays attached to the teat for several months until it is sufficiently developed to emerge.[15] Joeys are born with "oral shields"; in species without pouches or with rudimentary pouches these are more developed than in forms with well-developed pouches, implying a role in maintaining the young attached to the mother's nipple.[16]
Other animals
Many reptiles and the vast majority of invertebrates, most fish, amphibians and all birds are oviparous, that is, they lay eggs with little or no embryonic development taking place within the mother. In aquatic organisms, fertilization is nearly always external with sperm and eggs being liberated into the water (an exception is sharks and rays, which have internal fertilization[17]). Millions of eggs may be produced with no further parental involvement, in the expectation that a small number may survive to become mature individuals. Terrestrial invertebrates may also produce large numbers of eggs, a few of which may avoid predation and carry on the species. Some fish, reptiles, and amphibians have adopted a different strategy and invest their effort in producing a small number of young at a more advanced stage which are more likely to survive to adulthood. Birds care for their young in the nest and provide for their needs after hatching and it is perhaps unsurprising that internal development does not occur in birds, given their need to fly.[18]
A more developed form of
Among lizards, the
The majority of insects lay eggs but a very few give birth to offspring that are miniature versions of the adult.
See also
- Animal sexual behaviour
- Breeding season
- Caesarean section
- Dystocia
- Episiotomy
- Foaling (horses)
- Forceps delivery
- Kegel exercises
- Mating system
- Odon device
- Perineal massage
- Reproduction
- Reproductive system
- Ventouse
- Birth spacing
References
- OED Online. June 2013. Oxford University Press. Entry 19395 Archived 2022-11-22 at the Wayback Machine(accessed 30 August 2013).
- ^ ISBN 978-0-03-030504-7.
- ^ NICE (2007). Section 1.6, Normal labour: first stage
- ^ NICE (2007). Section 1.7, Normal labour: second stage
- ^ NICE (2007). Section 1.8, Normal labour: third stage
- ISBN 978-1-8561-3007-3.
- OL 9540216M.
- ^ Crockett, Gary (2011). "Humpback Whale Calves". Humpback whales Australia. Archived from the original on 2017-02-27. Retrieved 2013-08-28.
- ^ "Trunk Twins : Elephant Twins Born in Tarangire | Asilia Africa". Asilia Africa. 2018-04-06. Archived from the original on 2018-04-07. Retrieved 2018-04-06.
- ^ a b "Calving". Alberta: Agriculture and Rural Development. 2000-02-01. Archived from the original on 2013-09-12. Retrieved 2013-08-28.
- ^ "Calving Management in Dairy Herds: Timing of Intervention and Stillbirth" (PDF). The Ohio State University College of Veterinary Medicine Extension. 2012. Archived (PDF) from the original on 2013-12-19. Retrieved 2013-12-17.
- ^ from the original on 2016-11-18. Retrieved 2016-11-18.
- ^ Dunn, T.J. "Whelping: New Puppies On The Way!". Puppy Center. Pet MD. Archived from the original on 2018-08-24. Retrieved 2013-08-28.
- ISBN 978-0-521-33792-2.
- ^ "Reproduction and development". Thylacine Museum. Archived from the original on 2017-06-21. Retrieved 2013-08-28.
- PMID 21592102.
- ^ Sea World, Sharks & Rays Archived 2013-11-10 at the Wayback Machine; accessed 2013.09.09.
- ^ ISBN 9780002199124.
- S2CID 90834034. Archived from the originalon 2019-02-23. Retrieved 2019-06-30.
- ^ "Birth and care of young". Animals: Sharks and rays. Busch Entertainment Corporation. Archived from the original on August 3, 2013. Retrieved 2013-08-28.
- ISBN 978-0-691-03281-8.
- ISBN 978-0-691-03281-8.
- ^ Capinera, John L., Encyclopedia of entomology. Springer Reference, 2008, p. 3311.
- ^ Costa, James T., The Other Insect Societies. Belknap Press, 2006, p. 151.
- PMID 18509405.
- S2CID 205213348.
- ^ Kundinger, Heather. "Chamaeleo jacksonii (Jacksons chameleon)". Animal Diversity Web. Archived from the original on 2023-02-05. Retrieved 2023-02-27.
- S2CID 5191828.
- S2CID 85209921.
- ISSN 1095-8312.
- ^ Conrad, Jim (2011-12-10). "The aphid life cycle". The Backyard Nature Website. Archived from the original on 2019-03-18. Retrieved 2013-08-31.
Cited texts
- "Intrapartum care: Care of healthy women and their babies during childbirth". NICE. September 2007. Archived from the originalon 2014-04-26.