Childbirth, also known as labour, parturition and delivery, is the completion of pregnancy where one or more babies exits the internal environment of the mother via vaginal delivery or caesarean section.[7] In 2019, there were about 140.11 million human births globally.[9] In developed countries, most deliveries occur in hospitals,[10][11] while in developing countries most are home births.[12]
The most common childbirth method worldwide is vaginal delivery.[6] 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 cramping or also back pain in the case of back labour,[13] that typically lasts half a minute and occurs every 10 to 30 minutes.[14] Contractions gradually become stronger and closer together.[15] 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.[16] The fourth stage of labour involves the recovery of the mother, delayed clamping of the umbilical cord, and monitoring of the neonate.[17] As of 2014,[update] all major health organisations advise that immediately following a live birth, regardless of the delivery method, that the infant be placed on the mother's chest (termed skin-to-skin contact), and to delay neonate procedures for at least one to two hours or until the baby has had its first breastfeeding.[18][19][20]
Vaginal delivery is generally recommended as a first option. Cesarean section can lead to increased risk of complications and a significantly slower recovery. There are also many natural benefits of a vaginal delivery in both mother and baby. Various methods may help with pain, such as relaxation techniques, opioids, and spinal blocks.[15] It is best practice to limit the amount of interventions that occur during labour and delivery such as an elective cesarean section, however in some cases a scheduled cesarean section must be planned for a successful delivery and recovery of the mother. An emergency cesarean section may be recommended if unexpected complications occur or little to no progression through the birthing canal is observed in a vaginal delivery. Each year, complications from pregnancy and childbirth result in about 500,000 birthing deaths, seven million women have serious long-term problems, and 50 million women giving birth have negative health outcomes following delivery, most of which occur in the developing world.[5] Complications in the mother include obstructed labour, postpartum bleeding, eclampsia, and postpartum infection.[5] Complications in the baby include lack of oxygen at birth (birth asphyxia), birth trauma, and prematurity.[4][21]
The most prominent sign of labour is strong repetitive uterine contractions. Pain in contractions has been described as feeling similar to very strong menstrual cramps. Crowning may be experienced as an intense stretching and burning. The Lamaze method of childbirth teaches that making noises such as moaning, groaning, grunting, repeating words over and over, and any sound that one's body may wish to naturally make may help to relieve pain and help labour to progress. According to Lamaze, "While the media would have you believe that all birthing women scream, in reality, it's not the most common noise." They say that screaming may be a sign that the labouring woman is beginning to panic and the support team should help her back to regulated breathing.[22]
Back labour is a complication that occurs during childbirth when a fetus exhibits posterior presentation (i.e. when the fetus is facing the mother’s navel), instead of the typical anterior presentation.[23] This leads to more intense contractions, and causes pain in the lower back that persists between contractions as the fetus’ occiput exerts pressure on the mother’s sacrum.[24]
Another prominent sign of labour is the rupture of membranes, commonly known as "water breaking". During pregnancy, a baby is surrounded and cushioned by a fluid-filled sac. Usually the sac ruptures at the beginning of or during labour. It may cause a gush of fluid or leak in an intermittent or constant flow of small amounts from a woman's vagina. The fluid is clear or pale yellow. If the amniotic sac has not yet broken during labour the health care provider may break it in a technique called an amniotomy. In an amniotomy a thin plastic hook is used to make a small opening in the sac, causing the water to break.[25] If the sac breaks before labour starts, it's called a prelabour rupture of membranes. Contractions will typically start within 24 hours after the water breaks. If not, the care provider will generally begin labour induction within 24 to 48 hours. If the baby is preterm (less than 37 weeks of pregnancy), the healthcare provider may use a medication to delay delivery.[26]
There is currently no definitive scientific explanation for why labour is painful. According to studies, during pregnancy, the myometrium (the muscle part of the uterus) is greatly denervated.[27] Stretch receptors in the uterus disappear during pregnancy, and stretch receptors in the cervix disappear at the onset of labour.[28] Consequently, the reason for labour pain has only been theorised, not ascertained. One theory is that the pain results from the buildup of chemicals released during physical exertion. The second leading theory is that the pain results from the vasoconstriction of uterine blood vessels in the myometrium; each contraction squeezes the blood vessels, reducing blood flow and causing some hypoxia.
During the later stages of gestation, there is an increase in abundance of oxytocin, a hormone that is known to evoke feelings of contentment, reductions in anxiety, and feelings of calmness and security around the mate.[29] Oxytocin is further released during labour when the fetus stimulates the cervix and vagina, and it is believed that it plays a major role in the bonding of a mother to her infant and in the establishment of maternal behaviour. Studies show that the father of the child also has an increase in oxytocin levels following contact with the infant and parents with higher oxytocin levels showed more responsiveness and synchrony in their interactions with their infant. The act of nursing a child also causes a release of oxytocin to help the baby get milk more easily from the nipple.[30][31]
Station refers to the relationship of the fetal presenting part to the level of the ischial spines. When the presenting part is at the ischial spines the station is 0 (synonymous with engagement). If the presenting fetal part is above the spines, the distance is measured and described as minus stations, which range from −1 to −4 cm. If the presenting part is below the ischial spines, the distance is stated as plus stations ( +1 to +4 cm). At +3 and +4 the presenting part is at the perineum and can be seen.[32]
The fetal head may temporarily change shape (becoming more elongated or cone shaped) as it moves through the birth canal. This change in the shape of the fetal head is called molding and is much more prominent in women having their first vaginal delivery.[33]
Cervical ripening is the physical and chemical changes in the cervix to prepare it for the stretching that will take place as the fetus moves out of the uterus and into the birth canal. A scoring system called a Bishop score can be used to judge the degree of cervical ripening to predict the timing of labour and delivery of the infant or for women at risk for preterm labour. It is also used to judge when a woman will respond to induction of labour for a postdate pregnancy or other medical reasons. There are several methods of inducing cervical ripening which will allow the uterine contractions to effectively dilate the cervix.[34]
Vaginal delivery 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 4th stage of recovery which lasts until two hours after the delivery. The first stage is characterised by abdominal cramping or back pain that typically lasts around half a minute and occurs every 10 to 30 minutes.[14] The contractions (and pain) gradually becomes stronger and closer together.[15] The second stage ends when the infant is fully expelled. In the third stage, the delivery of the placenta.[16] The fourth stage of labour involves recovery, the uterus beginning to contract to pre-pregnancy state, delayed clamping of the umbilical cord, and monitoring of the neonatal tone and vitals.[17] As of 2014,[update] all major health organisations advise that immediately following a live birth, regardless of the delivery method, that the infant be placed on the mother's chest, termed skin-to-skin contact, and delaying routine procedures for at least one to two hours or until the baby has had its first breastfeeding.[18][19][20]
Definitions of the onset of labour include:
Many women are known to experience what has been termed the "nesting instinct". Women report a spurt of energy shortly before going into labour.[38] Common signs that labour is about to begin may include what is known as lightening, which is the process of the baby moving down from the rib cage with the head of the baby engaging deep in the pelvis. The pregnant woman may then find breathing easier, since her lungs have more room for expansion, but pressure on her bladder may cause more frequent need to void (urinate). Lightening may occur a few weeks or a few hours before labour begins, or even not until labour has begun.[38] Some women also experience an increase in vaginal discharge several days before labour begins when the "mucus plug", a thick plug of mucus that blocks the opening to the uterus, is pushed out into the vagina. The mucus plug may become dislodged days before labour begins or not until the start of labour.[38]
While inside the uterus the baby is enclosed in a fluid-filled membrane called the amniotic sac. Shortly before, at the beginning of, or during labour the sac ruptures. Once the sac ruptures, termed "the water breaks", the baby is at risk for infection and the mother's medical team will assess the need to induce labour if it has not started within the time they believe to be safe for the infant.[38]
The first stage of labour is divided into latent and active phases, where the latent phase is sometimes included in the definition of labour,[39] and sometimes not.[40]
The latent phase is generally defined as beginning at the point at which the woman perceives regular uterine contractions.[41] In contrast, Braxton Hicks contractions, which are contractions that may start around 26 weeks gestation and are sometimes called "false labour", are infrequent, irregular, and involve only mild cramping.[42] Braxton Hicks contractions are the uterine muscles preparing to deliver the infant.
Cervical effacement, which is the thinning and stretching of the cervix, and cervical dilation occur during the closing weeks of pregnancy. Effacement is usually complete or near-complete and dilation is about 5 cm by the end of the latent phase.[43] The degree of cervical effacement and dilation may be felt during a vaginal examination.
The active phase of labour has geographically differing definitions. The World Health Organization describes the active first stage as "a period of time characterised by regular painful uterine contractions, a substantial degree of cervical effacement and more rapid cervical dilatation from 5 cm until full dilatation for first and subsequent labours”.[44] In the US, the definition of active labour was changed from 3 to 4 cm, to 5 cm of cervical dilation for multiparous women, mothers who had given birth previously, and at 6 cm for nulliparous women, those who had not given birth before.[45] This was done in an effort to increase the rates of vaginal delivery.[46]
Health care providers may assess the mother's progress in labour by performing a cervical exam to evaluate the cervical dilation, effacement, and station. These factors form the Bishop score. The Bishop score can also be used as a means to predict the success of an induction of labour.
During effacement, the cervix becomes incorporated into the lower segment of the uterus. During a contraction, uterine muscles contract causing shortening of the upper segment and drawing upwards of the lower segment, in a gradual expulsive motion.[47] The presenting fetal part then is permitted to descend. Full dilation is reached when the cervix has widened enough to allow passage of the baby's head, around 10 cm dilation for a term baby.
A standard duration of the latent first stage has not been established and can vary widely from one woman to another. However, the duration of active first stage (from 5 cm until full cervical dilatation) usually does not extend beyond 12 hours in the first labour("primiparae"), and usually does not extend beyond 10 hours in subsequent labours ("multiparae").[48]
Dystocia of labour, also called "dysfunctional labour" or "failure to progress", is difficult labour or abnormally slow progress of labour, involving progressive cervical dilatation or lack of descent of the fetus. Friedman's Curve, developed in 1955, was for many years used to determine labour dystocia. However, more recent medical research suggests that the Friedman curve may not be currently[when?] applicable.[49][50]
The expulsion stage begins when the cervix is fully dilated, and ends when the baby is born. As pressure on the cervix increases, a sensation of pelvic pressure is experienced, and, with it, an urge to begin pushing. At the beginning of the normal second stage, the head is fully engaged in the pelvis; the widest diameter of the head has passed below the level of the pelvic inlet. The fetal head then continues descent into the pelvis, below the pubic arch and out through the vaginal opening. This is assisted by the additional maternal efforts of pushing, or bearing down, similar to defecation. The appearance of the fetal head at the vaginal opening is termed crowning. At this point, the mother will feel an intense burning or stinging sensation.
When the amniotic sac has not ruptured during labour or pushing, the infant can be born with the membranes intact. This is referred to as "delivery en caul".
Complete expulsion of the baby signals the successful completion of the second stage of labour. Some babies, especially preterm infants, are born covered with a waxy or cheese-like white substance called vernix. It is thought to have some protective roles during fetal development and for a few hours after birth.
The second stage varies from one woman to another. In first labours, birth is usually completed within three hours whereas in subsequent labours, birth is usually completed within two hours.[51] Second-stage labours longer than three hours are associated with declining rates of spontaneous vaginal delivery and increasing rates of infection, perineal tears, and obstetric haemorrhage, as well as the need for intensive care of the neonate.[52]
The period from just after the fetus is expelled until just after the placenta is expelled is called the third stage of labour or the involution stage. Placental expulsion begins as a physiological separation from the wall of the uterus. The average time from delivery of the baby until complete expulsion of the placenta is estimated to be 10–12 minutes dependent on whether active or expectant management is employed.[53] In as many as 3% of all vaginal deliveries, the duration of the third stage is longer than 30 minutes and raises concern for retained placenta.[54]
Placental expulsion can be managed actively or it can be managed expectantly, allowing the placenta to be expelled without medical assistance. Active management is the administration of a uterotonic drug within one minute of fetal delivery, controlled traction of the umbilical cord and fundal massage after delivery of the placenta, followed by performance of uterine massage every 15 minutes for two hours.[55] In a joint statement, World Health Organization, the International Federation of Gynaecology and Obstetrics and the International Confederation of Midwives recommend active management of the third stage of labour in all vaginal deliveries to help to prevent postpartum haemorrhage.[56][57][58]
Delaying the clamping of the umbilical cord for at least one minute or until it ceases to pulsate, which may take several minutes, improves outcomes as long as there is the ability to treat jaundice if it occurs. For many years it was believed that late cord cutting led to a mother's risk of experiencing significant bleeding after giving birth, called postpartum bleeding. However a recent review found that delayed cord cutting in healthy full-term infants resulted in early haemoglobin concentration and higher birthweight and increased iron reserves up to six months after birth with no change in the rate of postpartum bleeding.[59][60]
The fourth stage of labour is the period beginning immediately after childbirth, and extends for about six weeks. The terms postpartum and postnatal are often used for this period.[61] The woman's body, including hormone levels and uterus size, return to a non-pregnant state and the newborn adjusts to life outside the mother's body. The World Health Organization (WHO) describes the postnatal period as the most critical and yet the most neglected phase in the lives of mothers and babies; most deaths occur during the postnatal period.[62]
Following the birth, if the mother had an episiotomy or a tearing of the perineum, it is stitched. This is also an optimal time for uptake of long-acting reversible contraception (LARC), such as the contraceptive implant or intrauterine device (IUD), both of which can be inserted immediately after delivery while the woman is still in the delivery room.[63][64] The mother has regular assessments for uterine contraction and fundal height,[65] vaginal bleeding, heart rate and blood pressure, and temperature, for the first 24 hours after birth. Some women may experience an uncontrolled episode of shivering or postpartum chills following the birth. The first passing of urine should be documented within six hours.[62] Afterpains (pains similar to menstrual cramps), contractions of the uterus to prevent excessive blood flow, continue for several days. Vaginal discharge, termed "lochia", can be expected to continue for several weeks; initially bright red, it gradually becomes pink, changing to brown, and finally to yellow or white.[66]
At one time babies born in hospitals were removed from their mothers shortly after birth and brought to the mother only at feeding times.[67] Mothers were told that their newborns would be safer in the nursery and that the separation would offer the mothers more time to rest. As attitudes began to change, some hospitals offered a "rooming in" option wherein after a period of routine hospital procedures and observation, the infant could be allowed to share the mother's room. As of 2020, rooming-in has increasingly become standard practice in maternity wards.[68]
Skin-to-skin contact (SSC), sometimes also called kangaroo care, is a technique of newborn care where babies are kept chest-to-chest and skin-to-skin with a parent, typically their mother or possibly the father. This means without the shirt or undergarments on the chest of both the baby and parent. A 2011 medical review found that early skin-to-skin contact resulted in a decrease in infant crying, improved cardio-respiratory stability and blood glucose levels, and improved breastfeeding duration.[6