Uterus in the context of Fetus

The neck is the part of the body in many vertebrates that connects the head to the torso. It supports the weight of the head and protects the nerves that transmit sensory and motor information between the brain and the rest of the body. Additionally, the neck is highly flexible, allowing the head to turn and move in all directions. Anatomically, the human neck is divided into four compartments: vertebral, visceral, and two vascular compartments. Within these compartments, the neck houses the cervical vertebrae, the cervical portion of the spinal cord, upper parts of the respiratory and digestive tracts, endocrine glands, nerves, arteries⁣⁣ and veins. The muscles of the neck, which are separate from the compartments, form the boundaries of the neck triangles.

In anatomy, the neck is also referred to as the cervix or collum. However, when the term cervix is used alone, it often refers to the uterine cervix, the neck of the ⁣⁣uterus⁣⁣. Therefore, the adjective cervical can refer either to the neck (as in cervical vertebrae or cervical lymph nodes) or to the uterine cervix (as in cervical cap or cervical cancer).

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.

Sexual reproduction is a type of reproduction that involves a complex life cycle in which a gamete (haploid reproductive cells, such as a sperm or egg cell) with a single set of chromosomes combines with another gamete to produce a zygote that develops into an organism composed of cells with two sets of chromosomes (diploid). This is typical in animals, though the number of chromosome sets and how that number changes in sexual reproduction varies, especially among plants, fungi, and other eukaryotes.

In placental mammals, sperm cells exit the penis through the male urethra and enter the vagina during copulation, while egg cells enter the uterus through the oviduct. Other vertebrates of both sexes possess a cloaca for the release of sperm or egg cells.

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.

Dilation and evacuation (D&E) or dilatation and evacuation (British English) is the dilation of the cervix and surgical evacuation of the uterus (potentially including the fetus, placenta and other tissue) after the first trimester of pregnancy. It is the most common method and procedure for abortions in the second trimester of pregnancy. The procedure can also be used to remove a miscarried fetus from the womb.

In various health care centers it may be called by different names:

The intrauterine device (IUD), also known as an intrauterine contraceptive device (IUCD or ICD), is a small, T-shaped birth control device that is inserted into the uterus to prevent pregnancy. IUDs are a form of long-acting reversible contraception (LARC).

IUDs are a safe and effective birth control method that can be divided into two major categories based on the mechanism the device uses to prevent pregnancy: hormonal (levonorgestrel) IUDs and copper IUDs. Both types of IUDs can be used in most people with uteruses, including adolescents, those who have never been pregnant, and those who have previously had children. They do not affect breastfeeding and can be inserted immediately after delivery. They may also be used immediately after an abortion. Globally, 19.4% of women of reproductive age use intrauterine contraception according to 2019 data. The IUD has a more invasive insertion procedure than other birth control methods. However, among birth control methods, IUDs, along with other contraceptive implants, result in the greatest satisfaction among users.

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.

The cervical cap is a form of barrier contraception. A cervical cap fits over the cervix and blocks sperm from entering the uterus through the external orifice of the uterus, called the os.

Placental mammals (infraclass Placentalia /plæsənˈteɪliə/) are one of the three extant subdivisions of the class Mammalia, the other two being Monotremata and Marsupialia. Placentalia contains the vast majority of extant mammals, which are partly distinguished from monotremes and marsupials in that the fetus is carried in the uterus of its mother to a relatively late stage of development. The name is something of a misnomer, considering that marsupials also nourish their fetuses via a placenta, though for a relatively briefer period, giving birth to less-developed young, which are then nurtured for a period inside the mother's pouch. Placentalia represents the only living group within Eutheria, which contains all mammals that are more closely related to placentals than they are to marsupials.

Twins are two offspring produced by the same pregnancy. Twins can be either monozygotic ('identical'), meaning that they develop from one zygote, which splits and forms two embryos, or dizygotic ('non-identical' or 'fraternal'), meaning that each twin develops from a separate egg and each egg is fertilized by its own sperm cell. Since identical twins develop from one zygote, they will share the same sex, while fraternal twins may or may not. In very rare cases, fraternal or (semi-) identical twins can have the same mother and different fathers (heteropaternal superfecundation).

In contrast, a fetus that develops alone in the womb (the much more common case in humans) is a singleton; one of a multiple birth is a multiple. Unrelated look-alikes whose resemblance parallels that of twins are referred to as doppelgänger.

Implantation, also known as nidation, is the stage in the mammalian embryonic development in which the blastocyst hatches, attaches, adheres, and invades into the endometrium of the female's uterus. Implantation is the first stage of gestation, and, when successful, the female is considered to be pregnant. An implanted embryo is detected by the presence of increased levels of human chorionic gonadotropin (hCG) in a pregnancy test. The implanted embryo will receive oxygen and nutrients in order to grow.

For implantation to take place the uterus must become receptive. Uterine receptivity involves much cross-talk between the embryo and the uterus, initiating changes to the endometrium. This stage gives a synchrony that opens a window of implantation that enables successful implantation of a viable embryo. The endocannabinoid system plays a vital role in this synchrony in the uterus, influencing uterine receptivity, and embryo implantation. The embryo expresses cannabinoid receptors early in its development that are responsive to anandamide (AEA) secreted in the uterus. AEA is produced at higher levels before implantation and is then down-regulated at the time of implantation. This signaling is of importance in the embryo-uterus crosstalk in regulating the timing of embryonic implantation and uterine receptivity. Adequate concentrations of AEA that are neither too high or too low, are needed for successful implantation.

Caesarean section, also known as C-section, cesarean, or caesarean delivery, is the surgical procedure by which one or more babies are delivered through an incision in the mother's abdomen. It is often performed because vaginal delivery would put the mother or child at risk (of paralysis or even death). Reasons for the operation include, but are not limited to, obstructed labor, twin pregnancy, high blood pressure in the mother, breech birth, shoulder presentation, and problems with the placenta or umbilical cord. A caesarean delivery may be performed based upon the shape of the mother's pelvis or history of a previous C-section. A trial of vaginal birth after C-section may be possible. The World Health Organization recommends that caesarean section be performed only when medically necessary.

A C-section typically takes between 45 minutes to an hour to complete. It may be done with a spinal block, where the woman is awake, or under general anesthesia. A urinary catheter is used to drain the bladder, and the skin of the abdomen is then cleaned with an antiseptic. An incision of about 15 cm (5.9 in) is then typically made through the mother's lower abdomen. The uterus is then opened with a second incision and the baby delivered. The incisions are then stitched closed. A woman can typically begin breastfeeding as soon as she is out of the operating room and awake. Often, several days are required in the hospital to recover sufficiently to return home.

In mammals and other animals, the vagina (pl.: vaginas or vaginae) is the elastic, muscular reproductive organ of the female genital tract. In humans, it extends from the vulval vestibule to the cervix (neck of the uterus). The vaginal introitus is normally partly covered by a thin layer of mucosal tissue called the hymen. The vagina allows for copulation and birth. It also channels menstrual flow, which occurs in humans and closely related primates as part of the menstrual cycle.

To accommodate smoother penetration of the vagina during sexual intercourse or other sexual activity, vaginal moisture increases during sexual arousal in human females and other female mammals. This increase in moisture provides vaginal lubrication, which reduces friction. The texture of the vaginal walls creates friction for the penis during sexual intercourse and stimulates it toward ejaculation, enabling fertilization. Along with pleasure and bonding, women's sexual behavior with other people can result in sexually transmitted infections (STIs), the risk of which can be reduced by recommended safe sex practices. Other health issues may also affect the human vagina.