1. Introduction to the female reproductive system
2. Ovary and ovulation
3. Tuba uterina (uterine tube)
5. External female genitalia
6. Mamma (Mammary gland)
7. Cyclic changes during the menstrual cycle
8. Fertilization and cleavage
9. Pregnancy (gravidity)
Introduction to the female reproductive system
Ovaries, uterine tubes and uterus undergo periodic cyclic changes from puberty to menopause. Menarche is the initiation of menstrual cycle. The average age of menarche is between 9 and 14 years of age. From this moment are cyclic changes periodic. These structural and functional changes are under control of neurohumoral system. The cycle averages about 28 to 30 days in length. Between 45 and 50 years of age these periodic changes become irregular and eventually cease – menopause. Ovaries cease their reproductive (production of oocytes) and endocrine function.
Ovary and ovulation
Ovaries are paired, plum-shaped, whitish organ measuring about 3 cm in length, 1,5 cm in width and 1 cm in thickness. The surface of the ovary is smooth, but in reproductively mature woman is the surface distorted by scarring that follows the release of oocyte from follicle. The ovarian tissue is divisible into two different regions:
1) Medulla – is located in the central portion, it contains loose connective tissue with blood vessels, lymphatic vessels and nerves
2) Cortex – located in the peripheral portion surrounding the medulla. The boundary between medulla and cortex is indistinct. The cortex contains the ovarian follicles embedded in connective tissue. Follicles are present in various developmental stages, but each contains a single oocyte (germ cell).
The surface of the ovary is covered by a single layer of cuboidal epithelial cells – known as the germinal epithelium. This term came down from past when it was incorrectly thought to be the site of germ cell development. In actual fact are the primordial germ cells of extragonadal origin, they migrate into ovarian cortex from the embryonic yolk sac. Tunica albuginea is a layer of dense connective tissue between the germinal epithelium and ovarian cortex. It causes the whitish colouring of ovary.
Major functions of ovaries:
1) Developing and production of gametes – gametogenesis (in women, the production of gamete is called oogenesis, arised germ cell is called oocyte)
2) Steroidogenesis – syntheses of steroid hormones. Steroid hormones produced by ovaries:
a) Estrogens – are indispensable for growth and maturation of sex organs and are responsible for the developing of female sex characteristics. Estrogens also affect the development of mammary gland (stimulation of ductal proliferation and stromal growth + accumulation of adipose tissue)
b) Progesterones – prepare the internal sex organs (mainly the uterus) for pregnancy and also prepare the mammary gland for lactation (alveolar proliferation).
Each follicle contains a single oocyte, which is surrounded by one or more layers of follicle cells. These layer give rise to the membrana granulosa. Follicles undergo maturation in several developmental stages. Most of the follicles degenerate through atresia. Atresia can affect any developmental stage of follicles. By the beginning of reproductive life span remain in ovary about 400,000 oocytes. However only about 450 of them will ovulate during woman’s reproductive years. Histologically, three basic developmental stages of ovarian follicles can be distinguish:
1) Primordial follicles
2) Growing follicles
3) Mature follicles (Graafian follicles)
In the ovary, follicles are found at all developmental stages, but primordial follicles predominate.
Primordial follicles are the earliest stage of development. They first appear in ovary during the third month of intrauterine fetal development. In the mature ovary, primordial follicles are found just beneath the tunica albuginea. It consists of oocyte surrounded by a single layer of flattened follicle cells.
Primordial follicle: 1 – Oocyte of primordial follicle (arrow points to nucleus), 2 – Follicular cells
Growing follicle is further subcategorized into two developmental stages – primary and secondary (antral) follicles. During the maturation of follicle, some changes occur – the oocyte enlarges, flattened follicle cells proliferate and become cuboidal. In this moment is follicle identified as the unilaminar primary follicle. Follicle cells undergo mitotic proliferation and form stratified epithelium, the membrana granulosa. In this stage is follicle called the multilaminar primary follicle. Between oocyte and adjacent follicle cells, the thick extracellular coat is formed – zona pellucida. Stromal cells surrounding the follicle differentiate into sheet of connective tissue – theca folliculi (it is possible to distinguish theca interna and theca externa). During the further development, fluid-filled cavities appear among the granulosa cells – this fluid is called liquor folliculi. These cavities begin to coalesce and form proper cavity called antrum. Follicle in this stage is identified as the secondary (antral) follicle.
Multilayered primary follicle: 1 – Nucleus of oocyte and forming zona pellucida (arrows), 2 – Layers of follicular cells, 3 – Primordial follicle
Secondary follicle: 1 – Oocyte with nucleus (black arrow) and nucleolus (red arrow), 2 – Zona pellucida, 3 – Granulosa (=follicular) cells (arrows shows appearing cavities), 4 – Theca cells, 6 – Primary unilayered follicle, 7 – Primordial follicles
Mature follicle (Graafian follicle) has a diameter of 2,5 cm and it can be seen with the naked eye as translucent bulge on the surface of the ovary. Granulosa cells which surround the oocyte (have close contact with zona pellucida) are referred to as the corona radiata.
Ovulation is a hormone-mediated process resulting in the release of secondary oocyte from the ruptured Graafian follicle. A combination of hormonal and enzymatic effects is responsible for the release of the secondary oocyte in the middle of the menstrual cycle – on the 14th day of a 28-day cycle. The oocyte surrounded by the corona radiata is released from the ruptured Graafian follicle. Oocyte is caught by fimbriae of the uterine tube and is transported by the ciliated cells into the uterus. After ovulation, the secondary oocyte remains viable only for 24 hours. If fertilization does not occur, the secondary oocyte degenerates as it passes through the uterine tube. Normally, only one follicle completes maturation in each ovulation cycle. Rarely, more matured oocytes can be released in one cycle (that leads to the possibility of multiple pregnancy – dizygotic twins). Increased level of the luteinizing hormone (LH) is necessary for ovulation.
The primary oocyte in the primordial follicle begin the first meiotic division, but the process is arrested at the prophase of the first meiotic division. The first meiotic division is completed just before ovulation. Therefore, the primary oocyte remain arrested in the first meiotic prophase for 12 to 50 years. After the first meiotic division is complete, undergoes secondary oocyte the second meiotic division. This second meiotic division is arrested at the metaphase and completed only if the fertilization occurs.
After the ovulation, the follicular wall (comprised of remaining cells of membrana granulosa and cells of theca interna) collapses and forms the corpus luteum (luteal gland). At first, the bleeding from the capillaries in the theca interna into the follicular lumen appears, which leads to formation of the corpus hemorhagicum with cental clot. Subsequently, granulosa cells and theca interna cells undergo a morphologic changes – they differentiate into granulosa luteal cells and theca luteal cells (This process is called luteinization). Luteal cells are enlarged and filled with lipid droplets. Blood and lymphatic vessels from the theca interna rapidly grow into the membrana granulosa. Finally, the highly vascularized structure located in the cortex of the ovary is established – it is referred to as the corpus luteum. It constitutes a temporary endocrine gland – secretes progesterone and estrogens. These hormones stimulate growth and secretory activity of the lining cells of the uterine endometrium and prepare it for the implantation of fertilized ovum – zygote. If fertilization does not occur, the corpus luteum remains active only for 14 days and then begins to degenerate and undergoes the involution (corpus luteum menstruationis). If the fertilization occurs, the corpus luteum is stimulated by the human chorionic gonadotropin – hCG (is produced by trophoblast and lately by the placenta). In this case, the endocrine function of corpus luteum continues another 6 months and then gradually declines (corpus luteum graviditatis). In both cases, the involuted corpus luteum changes into white scar formed by dense collagenous material- corpus albicans.
Fallopian tube (uterine tube, tuba uterina)
Fallopian tube is paired tube approximately 10 to 12 cm long and 0,5 cm wide. Uterine tube transports the ovum from the ovary to the uterus and provide the necessary environment for fertilization and subsequent cleavage. One end of the tube (infundibulum) is adjacent to the ovary with fringed extensions (fimbriae) and opens into the peritoneal cavity. The other end communicates with the uterine cavity.
The wall of the uterine tube is composed of three layers:
1) The serosa (Tunica serosa) – outermost layer, is composed of the mesothelium and a thin layer of the connective tissue (Tela subserosa)
2) The muscle layer (Tunica muscularis) – organized into two layers (inner, thick circular layer and outer, thinner longitudinal layer
3) The mucosa (Tunica mucosa) – forms longitudinal folds projecting into the lumen of the uterine tube. These folds are most numerous and prominent in the ampulla – the most common site of the fertilization. Ampulla is the longest segment of the tube, constituting about two thirds of the total length. The mucosal lining is simple columnar epithelium composed of two kinds of cells – ciliated cells and nonciliated secretory cells, which produce fluid that provides nutrition and protection for the ovum. During the menstrual cycle, the epithelial cells undergo cyclic changes in response to hormonal (mainly estrogenic) influence. Specifically, it means cyclic hypertrophy during the follicular phase and atrophy during the luteal phase
Isthmus of the tube: 1 – Mucosal fold and lamina propria, 2 – Circular muscular layer, 3 – Longitudinal muscular layer, 4 – Tunica serosa with abundant vessels
Ampulla of the tube: 1 – Lamina propria, 2 – Epithelium
The uterine wall is composed of three layers. From the uterine lumen outward they are as follows:
1) The endometrium – the mucosa
2) The myometrium – the thick muscular layer
3) The perimetrium – the upper portion of the uterus is covered by the serosa (mesothelium + thin layer of loose connective tissue) and the lower portion by the adventitia (connective tissue).
Both myometrium and endometrium undergo cyclic changes each month during the menstrual cycle, preparing the uterus for implantation of the fertilized ovum.
Myometrium is thick layer of smooth muscle tissue. It is composed of three indistinctly defined layers:
1) The middle muscle layer – stratum vasculare contains numerous blood and lymphatic vessels, smooth muscle bundles are oriented in a circular pattern
2) The inner and outer layer has smooth muscle bundles oriented predominantly parallel to the long axis of the uterus
During the uterine contraction, all three layers work together as a functional syncytium. In the nonpregnant uterus, the smooth muscle bundle is about 50 μm long. During pregnancy undergoes the myometrium significant changes – hypertrophy (enlargement of existing smooth muscle cells to 500 μm) and hyperplasia (development of new muscle fibers from undifferentiated mesenchymal cells. After parturition, the uterus returns to almost it’s original size.
The endometrium proliferates and degenerates during the menstrual cycle. Changes of the endometrium are correlated with the maturation of the ovarian follicles. The end of each cycle is characterized by the destruction of the endometrium and by the discharge of tissue with menstrual blood. The menstrual cycle begins on the first day of the menstrual bleeding (see below).
The endometrium consists of two layers, which differ in function and structure. They are as follows:
1) The stratum functionale – thick part of the endometrium, which proliferates and degenerates during the menstrual cycle. It is cleared away during menstruation. During the menstrual cycle, the stratum functionale varies from 1 mm to 6 mm in thickness.
2) The stratum basale – this layer is retained during menstrual cycle, it is not sloughed off and subsequently proliferates and creates the new epithelium and lamina propria for the regeneration of the endometrium.
1 – Endometrium, 2 – Myometrium, 3 – Stratum basale, 4 – Stratum spongiosum starti functionalis, 5 – Stratum compactum strati functionalis, 6 – Glandulae uterales
The endometrial surface is lined by simple columnar epithelium composed of two kinds of cells – ciliated cells and nonciliated secretory cells. The epithelium invaginates into the underlying lamina propria (the endometrial stroma) forming the uterine glands – simple tubular glands – glandulae uterinae. Endometrial stroma is rich with fibroblasts.
1 – Lumen of the endometrial gland with secret, 2 – Epithelial cover of the gland, 3 – Lamina propria with stromal cells
The endometrium of the cervix differs from the rest of the uterus. The cervix uteri is the lowest part of the uterus. Mucosa contains branched mucous glands – cervical glands. The composition of mucus secreted by cervical glands vary under the influence of ovarian hormones during menstrual cycle. During the ovulation, the mucus is less viscous and more watery – that facilitates the penetration of sperm. In the luteal phase and during pregnancy, the mucus is more viscous due to the effect of progesterone, and it prevents the spread of microorganisms into the uterine body. The blockage of the openings of the mucosal glands by the stiff mucus causes the formation of dilated cyst called Nabothian cyst. The cervical endometrium lacks spiral arteries. During the menstrual cycle, the cervical endometrium undergoes only insignificant changes, and it is not sloughed off during menstruation. Vaginal portion of the cervix (the ectocervix) is lined by nonkeratinized stratified squamous epithelium.
The female external genitalia consist of the labia majora, labia minora, the clitoris and glands opening into the vestibulum vaginae.
The labia minora are composed of the loose connective tissue with elastic fibers and contains a lot of adipose tissue. The surface is lined by stratified squamous epithelium with the thin layer of keratinized cells. Large sebaceous and sweat glands are present.
The labia majora are also composed of loose collagenous connective tissue with a thin layer of smooth muscle cells. The surface is covered by skin. The outer surface is thicker and contains pubic hair, sebaceous glands and sweat glands (eccrine and apocrine). The inner surface is thinner and also contains sebaceous and sweat glands.
The clitoris is covered by stratified squamous keratinized epithelium. It is composed of two small erectile bodies (corpora cavernosa).
Greater vestibular glands – Bartholin’s glands (glandulae vestibulares majores)
Bartholin’s glands are ovoid-shaped tuboalveolar glands with mucosal cells. They are homologous to the male bulbourethral glands. Another glands are lesser vestibular glands – Skene’s glands (glandulae vestibulares minores), which open into the vestibulum around the urethra.
Mammary gland (glandula mammaria)
Histological structure and visual aspect of breast naturally vary according to the age and functional state of the gland.
This is micrograph of an HE-stained inactive mammary gland. Try to compare it with the following slide, which shows an active mammary gland during lactation, also stained by HE.
The mammary gland is composed of 20 tubuloalveolar glandular lobes separated by dense collagenous connective tissue and adipose tissue. In the axis of each glandular lobe is the lactiferous duct (ductus lactifer) which is about 2 cm to 4 cm long and opens into the nipple. The lactiferous duct is lined by two layers of cuboidal or columnar epithelium with myoepithelial cells. Into these lactiferous ducts open the interlobular ducts lined by simple cuboidal epithelium. In the inactive gland before puberty consists the mammary gland chiefly of the lactiferous duct elements and few lobular branches. During the puberty the ductal system undergoes branching and terminal ductules and secretory lobules appear. It is exactly the presence of secretory lobules, which defines the structure of mature mammary gland. Lobules are surrounded by loose connective tissue with lymphocytes and plasma cells. Morphological growth is caused by accumulation of adipose tissue and collagen connective tissue due to the increased level of estrogens during puberty. If the pregnancy occurs, the elongation and branching of the terminal ductules appear. From the growing ends of the terminal ductules differentiate alveoli surrounded by 4 to 6 myoepithelial cells. The lining epithelial cells of alveoli differentiate into active secretory cells with prominent rough endoplasmic reticulum, Golgi apparatus and numerous mitochondria. The growth during pregnancy is affected by many factors, in the first place by hormones – estrogens, progesterones, prolactin, human chorionic gonadotropin – hCG.
The breast milk is produced by epithelial alveolar secretory cells. It is stored in lumen of alveoli and in lumen of lactiferous ducts. In the cytoplasm of secretory cells are prominent secretory granules containing proteins, chiefly lactalbumin and casein, released by merocrine secretion. The plasma cells produce the secretory IgA, that provide the newborn his first passive immune defence. Just after the end of lactation, most of alveolar cells degenerate and they are phagocytosed by macrophages. The myoepithelial cells are not degraded and they are used in the case of the next pregnancy.
After menopause, the mammary gland involutes and individual parts atrophy.
The nipple is covered by the stratified squamous keratinized epithelium. This epithelium contains melanocytes, which store the melanin (especially during pregnancy). The stroma is composed of smooth muscle tissue, which is in the deeper layers oriented in the circular pattern around the lactiferous ducts. In the superficial layers is smooth muscle oriented more parallel around the ducts.
Cyclic changes during the menstrual cycle
The female reproductive systém undergoes cyclic changes, which are caused by the coaction of the hypothalamus (gonadotropin-releasing hormone – GnRH, affects the production of hormones in adenohypophysis), adenohypophysis (FSH – Follicle-stimulating hormone, LH – Luteinizing hormone) and reproductive organs (Estrogens, Progesterone). Depending on the site, where these cyclic changes occur, can we distinguish several kinds of cycle – ovarian (ovulation), uterine (menstrual), cervical, vaginal.
Changes of the ovary – Ovarian cycle
One ovarian cycle lasts about 28 days in length (But it could average about 24 to 36 days). The ovarian cycle is divided into three phases:
First phase – Follicular
It lasts between 12 to 14 days from the first day of the last menstrual bleeding. FSH produced from adenohypophysis stimulates one of the follicles to enlarge, mature and develop into the Graafian follicle. This mature follicle bulges above the ovarian surface. In this phase, the follicle cells produce estrogens and a low level of progesterone.
Second phase – Ovulation (14th day of the cycle)
The Graafian follicle ruptures and the ovum is released into the peritoneal cavity, where is caught by fimbriae of uterine tube.
Third phase – Luteal (15th to 28th day of the cycle)
After the release of the ovum, the remains of follicle convert into the corpus luteum which produces progesterone and prepares the reproductive organs for pregnancy. If there is no fertilization, the corpus luteum degenerates on 24th day of the cycle and on it’s place remains tiny scar.
Endometrial changes – menstrual cycle
The menstrual cycle is the complex of cyclic endometrial changes. It repeats periodically each 28 days. During this cycle, the endometrium undergoes significant morphologic and functional changes. These changes are caused by effect of ovarian hormones (estrogens and progesterone) which are controlled by adenohypophysis. The beginning of the menstrual cycle is defined as the first day of the menstrual bleeding. The menstrual cycle is divided into four phases:
It lasts the first four days of the cycle. If fertilization does not occur, the corpus luteum ceases to produce progesterone after 14 days. The blood level of progesterone rapidly decreases. It causes the involution of the endometrium. The stratum functionale of endometrium is sloughed with 35 – 50 ml of menstrual blood.
Proliferative phase (5th to 14th day of the cycle)
This phase is caused by effect of estrogens. It continues simultaneously with the follicle maturing (the follicular phase of the ovarian cycle). After the menstrual phase, the endometrium is reduced to the thin (about 1 mm) stipe of connective tissue (lamina propria) containing the basal portions of uterine glands and the lower parts of spiral arteries. The stratum functionale of endometrium regenerates, epithelial cells and cells of the connective tissue stroma proliferate and produce the collagen. Spiral arteries lengthen – are slightly coiled and they reach only into the basal two thirds of the endometrium. At the end of this phase, the endometrium is about 3 mm thick, the glands are straight and they have prominent lumen.
Secretory phase (15th to 27th day of the cycle)
The secretory phase is induced by progesterone produced by the corpus luteum. Progesterone stimulates glands to produce glycoproteins. The glands changes, become coiled and their lumen is widened due to the accumulated secretion.The epithelial cell begin to store glycogen. In this phase, the endometrium is about 5 mm to 6 mm thick. Mitosis are rare. The coiled arteries lengthen and they pervade to the surface of endometrium. Now is the uterus prepared for implantation of fertilized ovum.
Ischemic phase (28th day of the cycle)
This phase lasts only few hours. If there is no fertilization, corpus luteum degenerates and the production of progesterone ceases. The contraction of mucosal arteries due to the decreased level of progesterone causes ischemia of endometrial cells and afterward, these cells degenerate.
The secretion of sex hormones is under control of hypothalamic-pituitary axis. Gonadotropin-releasing hormone (GnRH) produced by hypothalamus stimulates hormonal secretion from adenohypophysis. Depending on hypothalamic stimulation, the adenohypophysis secrete two hormones:
1) Luteinizing hormone (LH) – due to it’s effect are ovaries stimulated to produce estrogens, release the mature ovum (ovulation) and create the corpus luteum.
2) Follicle-stimulating hormone (FSH) – it affects the development and maturation of follicles.
1) Estrogens – produced by the follicle cells in ovaries. These hormones are important for development of the reproductive organs and induce the proliferative phase of the menstrual cycle.
2) Progesterone – produced by the corpus luteum, during pregnancy also by placenta. It is responsible for the secretory phase of the menstrual cycle, decreases the uterine contractility during pregnancy, stimulates the growth of alveoli in mammary gland and increases the basal temperature.
Fertilization and cleavage
Just before we focus on the processes in the ovum, it is important to explain capacitation. It is the activation process of spermatozoa within the female reproductive system. Capacitation involves biochemical structural and functional changes to the sperm that result in the increased ability to penetrate the zona pellucida and fertilize the ovum.
Usually, only a few hundred (of about 200 to 300 millions sperm in an ejaculate) of spermatozoa reach the site of fertilization, typically the ampulla of the uterine tube. Sperm cells must penetrate the corona radiata and zona pellucida. Only one sperm cell penetrates the ovum. Before sperm cell can fertilize the ovum, it must undergo the process of capacitation. In this process, the sperm cells acquire the ability to bind to zona pellucida receptors. Binding to these receptors on the zona pellucida triggers the acrosome reaction in which enzymes are released from the acrosome and enable sperm cell to penetrate the zona pellucida. At the same time, the the cortical reaction (zona reaction) is initiated. The releasing of cortical granules (containing proteases) causes inactivation of zona pellucida receptors. That prevents the fusion of multiple sperms with on ovum (polyspermy). The impregnation of the oocyte induce termination of the second meiotic division.
The result of fertilization is restoration of a diploid complement of 46 chromosomes, embryonal sex determination (sperm cell with the Y chromosome determines male and the X chromosome determines female), and the beginning of cleavage.
During the fertilization (the fusion of gametes), the zygote is formed. Zygote contains a diploid complement of chromosomes. As it passes through the uterine tube into the uterine cavity, the zygote undergoes cleavage – blastogenesis. It comprises of series of mitotic divisions without cell growth, resulting in a rapid increase in the cell number. These individual cells – blastomeres – become smaller while their number increases. The human embryo formed by 12 to 15 blastomeres is called a morula. The morula arises during the third day after fertilization and it enters into the uterus. If the uterus is prepared, the morula is caught and embedded in the uterine mucosa – implantation.
During 4th day after fertilization, the fluid-filled cavity is formed in the centre of the morula. This cavity (blastocyst cavity) defines the beginning of the blastocyst. Blastocyst cavity begins enlarge and divides the cell mass into two parts:
1) The outer cell mass – trophoblast gives rise to the extraembryonic structures and the fetal portion of placenta
2) The inner cell mass – embryoblast gives rise to the human embryo
At the end of the first week is the blastocyst superficially embedded in the endometrium. The most common site of implantation is the cranial third of anterior or posterior wall of the uterine body.
Human pregnancy lasts about 280 days (it averages between 266 and 294 days). It is counted from the first day of the last menstrual cycle. The gravidity is divided into three trimesters. The term birth (partus maturus) is defined as delivery of a baby between 38 and 42 weeks of gestation. Partus praematurus (preterm birth) is birth of a baby of less than 37 weeks of gestation. The first sign of pregnancy is often the amenorrhea – the absence of menstrual period. But gravidity can also be accompanied by minor periodic bleeding. The certain sign is a positive test result for human chorionic gonadotropin (hCG). It is a glycoprotein produced by syncytiotrophoblast. The pregnancy tests are based on hCG detection in the maternal blood or urine and they can recognize the concentration of hCG from 7th or 8th day after fertilization. The identification of embryo by using vaginal ultrasonography is possible in about 4th week of pregnancy. From the 6th week can be also by using USG recognized the embryonic heart action. The gestational (also called menstrual) age of pregnancy means that the the initiation of pregnancy is the first day of the last normal menstrual period (LMP). Nevertheless, the fertilization occurs about two weeks later (after ovulation). The fetal age (also called embryonal) is the actual biological age of embryo counting from the time of fertilization and it is used especially by embryologists. In the gynaecological terminology is preferred the gestational age counted in weeks. The relation between fetal (embryonal) and gestational age:
Fetal (embryonal) age = gestational (menstrual) age – two weeks
The example from gynaecological documentation record: pregnancy lasting 5 + 3 means that it is 5 weeks and 3 days from the first day of the last menstrual period and now is the pregnancy in ongoing 6th week. The calculation of the birth term:
The date of the first day of the last menstrual period – 3 months + 7 days
For example: the first day of the last menstrual period was 3. 4. 2013, the birth term is than 10. 1. 2014.
Changes during pregnancy
1) The average gain in weight during pregnancy is 11 kg. (approximately 3 kg by growing fetus, 2 kg placenta and liquor amnii, 2 kg enlarging uterus and breasts, 2 kg fat accumulation and 2 kg extracellular fluid retention). The most noticeable gain in weight is during the third trimester. The retained fluid is eliminated with urine in the first days after delivery.
2) The 15% increase of basal metabolism (due to the increased secretion of thyroxine and and adrenocortical hormones)
3) The increase of cardiac output by 30 – 40 % and increase in heart rate by 10 to 15 per minute
4) The 30% increase in the blood volume (due to the increased secretion of aldosterone and estrogens during pregnancy – aldosterone and estrogens cause the retention of ions and water in the kidneys)
5) The increased erythrocyte sedimentation rate
6) The increased respiraory minute volume (the minute ventilation)
7) The increased kidney blood flow and glomerular filtration
Before the actual delivery, the lie, presentation and holding of the fetus are defined. Even today in the age of ultrasounds, every obstetrician should be able to describe this using an external palpation of pregnant woman. Lie of the fetus is the relationship between long axis of the fetus and the longitudinal (“long”) axis of the uterus. There are 3 types of fetal lies – longitudinal (long axis of the fetus is parallel to the long axis of the uterus), transverse and oblique. However, only longitudinal lie can be spontaneously delivered. The others are delivered surgically (or manually turning the fetus into the longitudinal lie). The longitudinal lie is in 95 % cephalic (fetal head is faced down) and in remaining cases, we are talking about the longitudinal lie breech presentation.
The labour itself is divided into four phases or periods of delivery (in some literature, only three phases are distinguished – the last phase is not separated).
The first phase of labor – Opening
During the first phase of labour, the cervix is shorten and dilated. This phase is the longest period of labour. It takes about 12 to 14 hours in nulliparous woman (women giving birth for the first time) and 6-8 hours in women who have already given birth. In the end of pregnancy, the cervix becomes soft and pliable, allowing the dilatation during contractions. In this phase of delivery, most frequently occurs the rupture of fetal membranes (rupture of membranes may occur long before the onset of contractions, or on the other hand, does not occur even after dilatation of the cervix – in this case, the rupture of the fetal membranes must be performed by obstetrician).
The second stage of labor – Expulsion
At this stage of labor, the actual delivery of the fetus comes about. This phase begins with complete dilatation of the cervix and ends with the expulsion of the fetus from the mother’s body. The entire phase lasts a few minutes. The second period of delivery significantly facilitated by the episiotomy. Except the speed-up of the second stage of labour is also performed to prevent tearing of the perineum. Episiotomy can be distinguished into lateral (oblique cutting line) or median (cutting line toward the rectum). Median episiotomy is not performed anymore because of increased risk of rectal injury. Episiotomy must be performed during contraction. Decision whether to proceed episiotomy or not depends on consideration of the obstetrician with consideration of the birth process and monitored status of the fetus (see below).
The physiological movements of the fetus during pass through the small pelvis are: progression of head, flexion of head, internal rotation, deflection, external rotation, followed by delivery of arms.
The third stage of labor – Delivery of placenta
After the birth of the fetus, the uterus contract further, resulting in the separation and delivery of the placenta. It is necessary to control the integrity of the placenta to exclude any part of its retention within the uterus. Also is important to control the umbilical cord, which should contain 2 small arteries and 1 large vein. (In the case of only one artery and one vein presented in umbilical cord is an increased risk of congenital heart defects of fetus)
The fourth stage – Postpartum
The fourth period takes about two hours. During this time, the woman is still observed in the delivery room to prevent late complications.
Uterine contractions during labour originate in the fundus and spreads through the body caudally to the uterine cervix. Latent and active phases of labour are distinguished. The latent stage of labor refers to that when cervical dilation does not exceed 4 cm. Cervical dilation progresses very slowly. There can be present contraction, which may or may not be painful (this phase can be recognized even by the fact that the mother during contractions can talk and laugh). The latent stage of labor can last for several days. If no rupture of membranes occurs, there is no reason for admit to the hospital. The active stage of labour should be immediately admitted to the hospital. The contractions become regular and painful. The woman is not able to speak during contraction anymore. Dilation of the cervix is now 1.2 to 1.5 cm / hr.
During contraction, blood flow to the placenta is reduced. It is very important to monitor the fetus during the delivery using cardiotocography that monitors heart activity of the fetus depending on the uterine contraction. Each entry has clinical importance, which is immediately interpretable. Physiological fetal heart rate is 120-160. Decrease below this limit is a sign of threatening fetal hypoxia.
Immediately after birth, the newborn is scored. This method is called APGAR score, which assesses: skin color, pulse, reaction to irritation, muscle tension and breath rate of the newborn. The maximum number of points is 10 – 2 for each property. APGAR is evaluated immediately after delivery, then after 5 minutes and after 10 minutes.
Subchapter Authors: Lucie Nováková and Bětka Blanková