Fetus in the context of Hydrops fetalis

The right to life is the belief that a human (or other animal) has the right to live and, in particular, should not be killed by another entity. The concept of a right to life arises in debates on issues including: capital punishment, with some people seeing it as immoral; abortion, with some considering the killing of a human embryo or fetus immoral; euthanasia, in which the decision to end one's life outside of natural means is seen as incorrect; meat production and consumption, in which the breeding and killing of animals for their meat is seen by some people as an infringement on their rights; and in killings by law enforcement, which are seen by some as an infringement on those persons' right to live. However, individuals may disagree in which of these areas the principle of a right to life might apply.

Abortion is the termination of a pregnancy by removal or expulsion of an embryo or fetus. The unmodified word abortion generally refers to induced abortion, or deliberate actions to end a pregnancy. Abortion occurring without intervention is known as spontaneous abortion or "miscarriage", and occurs in roughly 30–40% of all pregnancies. Common reasons for inducing an abortion are birth-timing and limiting family size. Other reasons include maternal health, an inability to afford a child, domestic violence, lack of support, feelings of being too young, wishing to complete an education or advance a career, and not being able, or willing, to raise a child conceived as a result of rape or incest.

When done legally in industrialized societies, induced abortion is one of the safest procedures in medicine. Modern methods use medication or surgery for abortions. The drug mifepristone (aka RU-486) in combination with prostaglandin appears to be as safe and effective as surgery during the first and second trimesters of pregnancy. Self-managed medication abortion is highly effective and safe throughout the first trimester. The most common surgical technique involves dilating the cervix and using a suction device. Birth control, such as the pill or intrauterine devices, can be used immediately following an abortion. When performed legally and safely on a woman who desires it, an induced abortion does not increase the risk of long-term mental or physical problems. In contrast, unsafe abortions performed by unskilled individuals, with hazardous equipment, or in unsanitary facilities cause between 22,000 and 44,000 deaths and 6.9 million hospital admissions each year — responsible for between 5% and 13% of maternal deaths, especially in low-income countries. The World Health Organization states that "access to legal, safe and comprehensive abortion care, including post-abortion care, is essential for the attainment of the highest possible level of sexual and reproductive health". Public health data show that making safe abortion legal and accessible reduces maternal deaths.

Pregnancy is the time during which one or more offspring gestates inside a woman's uterus. A multiple pregnancy involves more than one offspring, such as with twins.

Conception usually occurs following vaginal intercourse, but can also occur through assisted reproductive technology procedures. A pregnancy may end in a live birth, a miscarriage, an induced abortion, or a stillbirth. Childbirth typically occurs around 40 weeks from the start of the last menstrual period (LMP), a span known as the gestational age; this is just over nine months. Counting by fertilization age, the length is about 38 weeks. Implantation occurs on average 8–9 days after fertilization. An embryo is the term for the developing offspring during the first seven weeks following implantation (i.e. ten weeks' gestational age), after which the term fetus is used until the birth of a baby.

Childbirth, also known as labour (or labor in American English), parturition, and delivery, is the completion of pregnancy, where one or more fetuses exits the internal environment of the mother via vaginal delivery or caesarean section and becomes a newborn to the world. In 2019, there were about 140.11 million human births globally. In developed countries, most deliveries occur in hospitals, while in developing countries most are home births.

The most common childbirth method worldwide is vaginal delivery. It involves four stages of labour: the shortening and opening of the cervix during the first stage, descent and birth of the baby during the second, the delivery of the placenta during the third, and the recovery of the mother and infant during the fourth stage, which is referred to as the postpartum. The first stage is characterised by abdominal partying or also back pain in the case of back labour, that typically lasts half a minute and occurs every 10 to 30 minutes. Contractions gradually become stronger and closer together. Since the pain of childbirth correlates with contractions, the pain becomes more frequent and strong as the labour progresses. The second stage ends when the infant is fully expelled. The third stage is the delivery of the placenta. The fourth stage of labour involves the recovery of the mother, delayed clamping of the umbilical cord, and monitoring of the neonate. All major health organisations advise that immediately after giving birth, regardless of the delivery method, that the infant be placed on the mother's chest (termed skin-to-skin contact), and to delay any other routine procedures for at least one to two hours or until the baby has had its first breastfeeding.

Prenatal development (from Latin natalis 'relating to birth') involves the development of the embryo and of the fetus during a viviparous animal's gestation. Prenatal development starts with fertilization, in the germinal stage of embryonic development, and continues in fetal development until birth. The term "prenate" is used to describe an unborn offspring at any stage of gestation.

In human pregnancy, prenatal development is also called antenatal development. The development of the human embryo follows fertilization, and continues as fetal development. By the end of the tenth week of gestational age, the embryo has acquired its basic form and is referred to as a fetus. The next period is that of fetal development where many organs become fully developed. This fetal period is described both topically (by organ) and chronologically (by time) with major occurrences being listed by gestational age.

Gestation is the period of development during the carrying of an embryo, and later fetus, inside viviparous animals (the embryo develops within the parent). It is typical for mammals, but also occurs for some non-mammals. Mammals during pregnancy can have one or more gestations at the same time, for example in a multiple birth.

The time interval of a gestation is called the gestation period. In obstetrics, gestational age refers to the time since the onset of the last menses, which on average is fertilization age plus two weeks.

In religion and ancient philosophy, ensoulment (from the verb ensoul meaning to endow or imbue with a soul -- earliest ascertainable word use: 1605) is the moment at which a human or other being gains a soul. Some belief systems maintain that a soul is newly created within a developing child; others, especially in religions that believe in reincarnation, believe that the soul is pre-existing and enters the body at a particular stage of development.

In the time of Aristotle, it was widely believed that the human soul entered the forming body at 40 days (male embryos) or 90 days (female embryos), and quickening was an indication of the presence of a soul. Other religious views are that ensoulment happens at the moment of conception; or when the child takes the first breath after being born; at the formation of the nervous system and brain; at the first detectable sign of brain activity; or when the fetus is able to survive independently of the uterus (viability).

Miscarriage, also known in medical terms as a spontaneous abortion, is an end to pregnancy resulting in the loss and expulsion of an embryo or fetus from the womb before it can survive independently. Miscarriage before 6 weeks of gestation is defined as biochemical loss by ESHRE. Once ultrasound or histological evidence shows that a pregnancy has existed, the term used is clinical miscarriage, which can be "early" (before 12 weeks) or "late" (between 12 and 21 weeks). Spontaneous fetal termination after 20 weeks of gestation is known as a stillbirth. The term miscarriage is sometimes used to refer to all forms of pregnancy loss and pregnancy with abortive outcomes before 20 weeks of gestation.

The most common symptom of a miscarriage is vaginal bleeding, with or without pain. Tissue and clot-like material may leave the uterus and pass through and out of the vagina. Risk factors for miscarriage include being an older parent, previous miscarriage, exposure to tobacco smoke, obesity, diabetes, thyroid problems, and drug or alcohol use. About 80% of miscarriages occur in the first 12 weeks of pregnancy (the first trimester). The underlying cause in about half of cases involves chromosomal abnormalities. Diagnosis of a miscarriage may involve checking to see if the cervix is open or sealed, testing blood levels of human chorionic gonadotropin (hCG), and an ultrasound. Other conditions that can produce similar symptoms include an ectopic pregnancy and implantation bleeding.

A woman is an adult female human. Before adulthood, a female child or adolescent is referred to as a girl.

Typically, women inherit a pair of X chromosomes, one from each parent. Sex differentiation of the female fetus is governed by the lack of a present functioning SRY gene on either one of the respective sex chromosomes. Female anatomy is distinguished from male anatomy by the female reproductive system, which includes the ovaries, fallopian tubes, uterus, vagina, and vulva. A woman generally has a wider pelvis, broader hips, and larger breasts than a man. These characteristics can facilitate pregnancy, childbirth and breastfeeding. Women typically have less facial and other body hair, have a higher body fat composition, and are on average shorter and less muscular than men. Women are at greater risk of certain diseases like breast cancer, and at lower risk of other diseases like lung cancer.

An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell – a zygote. Within the vessel, an embryo is incubated until it has become an animal fetus that can survive on its own, at which point the animal hatches. Reproductive structures similar to the egg in other kingdoms are termed "spores", or in spermatophytes "seeds", or in gametophytes "egg cells".

Most arthropods, vertebrates (excluding live-bearing mammals), and mollusks lay eggs, although some, such as scorpions, do not. Reptile eggs, bird eggs, and monotreme eggs are laid out of water and are surrounded by a protective shell, either flexible or inflexible. Eggs laid on land or in nests are usually kept within a warm and favorable temperature range while the embryo grows. When the embryo is adequately developed it hatches; i.e., breaks out of the egg's shell. Some embryos have a temporary egg tooth they use to crack, pip, or break the eggshell or covering.

The uterus (from Latin uterus, pl.: uteri or uteruses) or womb (/wuːm/) is the organ in the reproductive system of most female mammals, including humans, that accommodates the embryonic and fetal development of one or more fertilized eggs until birth. The uterus is a hormone-responsive sex organ that contains glands in its lining that secrete uterine milk for embryonic nourishment. (The term uterus is also applied to analogous structures in some non-mammalian animals.)

In humans, the lower end of the uterus is a narrow part known as the isthmus that connects to the cervix, the anterior gateway leading to the vagina. The upper end, the body of the uterus, is connected to the fallopian tubes at the uterine horns; the rounded part, the fundus, is above the openings to the fallopian tubes. The connection of the uterine cavity with a fallopian tube is called the uterotubal junction. The fertilized egg is carried to the uterus along the fallopian tube. It will have divided on its journey to form a blastocyst that will implant itself into the lining of the uterus – the endometrium, where it will receive nutrients and develop into the embryo proper, and later fetus, for the duration of the pregnancy.

Embryology (from Greek ἔμβρυον, embryon, "the unborn, embryo"; and -λογία, -logia) is the branch of zoology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses. Embryology includes teratology, the study of congenital disorders that occur before birth.

Early embryology was proposed by Marcello Malpighi, and known as preformationism, the theory that organisms develop from pre-existing miniature versions of themselves. Aristotle proposed the now-accepted theory of epigenesis, the idea that organisms develop from seed or egg in a sequence of steps. Modern embryology developed from the work of Karl Ernst von Baer, though accurate observations had been made in Italy by anatomists such as Aldrovandi and Leonardo da Vinci in the Renaissance.

Intrauterine growth restriction (IUGR), or fetal growth restriction, is the poor growth of a fetus while in the womb during pregnancy. IUGR is defined by clinical features of malnutrition and evidence of reduced growth regardless of an infant's birth weight percentile. The causes of IUGR are broad and may involve maternal, fetal, or placental complications.

At least 60% of the 4 million neonatal deaths that occur worldwide every year are associated with low birth weight, caused by intrauterine growth restriction (IUGR), preterm delivery, and genetic abnormalities, demonstrating that under-nutrition is already a leading health problem at birth.

A vertically transmitted infection is an infection caused by pathogenic bacteria or viruses that use mother-to-child transmission, that is, transmission directly from the mother to an embryo, fetus, or baby during pregnancy or childbirth. It can occur when the mother has a pre-existing disease or becomes infected during pregnancy. Nutritional deficiencies may exacerbate the risks of perinatal infections. Vertical transmission is important for the mathematical modelling of infectious diseases, especially for diseases of animals with large litter sizes, as it causes a wave of new infectious individuals.