In a woman's body, there are four hormones that share the role of initiating and supporting the process of labour and birth. These hormones are oxytocin, endorphins, adrenaline and prolactin. The labouring mother's mental and physical condition, as well as her environment, can affect the release and effectiveness of these hormones in assisting, or in some cases disrupting, the birth process. Endorphins are "endogenous opioids secreted by the pituitary gland that act on the central and peripheral nervous system to reduce pain," (Lowdermilk & Perry, 2007). Levels of endorphins increase during labor and birth to "help women tolerate acute pain and reduce irritability and anxiety," (Lowdermilk & Perry, 2007). Prolactin is produced by the anterior pituitary and is responsible for initial lactation. Adrenaline is also released during labor, although the adrenal gland remains relatively unchanged throughout pregnancy. However it is oxytocin that plays one of the largest and most important roles in the birthing process. Because it is involved during love making, birthing, breastfeeding, and bonding, oxytocin is often referred to as "The Love Hormone."
Oxytocin is produced in the reproduction organs of mammals (ovaries in females and testes in male and in the posterior pituitary gland. Serum oxytocin begins to increase amounts as the fetus matures. This hormone can stimulate uterine contraction during pregnancy, but high levels of progesterone can prevent contractions until near term.
At the end of gestation, the uterus must contract vigorously and for a prolonged period of time in order to deliver the fetus. During the later stages of gestation, there is an increase in abundance of oxytocin receptors on uterine smooth muscle cells, which is associated with increased "irritability" of the uterus (and sometimes the mother as well). Oxytocin is released during labor when the fetus stimulates the cervix and vagina, and it enhances contraction of uterine smooth muscle to facilitate parturition or birth (Bowen, 2007). Oxytocin is a potent stimulator of contractions, which help to dilate the cervix, move the baby down and out of her body, give birth to her placenta, and limit bleeding at the site of the placenta. During labor and birth, the pressure of the baby against the cervix and then against tissues in the pelvic floor stimulates oxytocin and contractions (childbirthconnection.com, 2007).
Many factors can hinder oxytocin release, among them stress, for example during frightfulness (i.e. transfer from home to hospital, shift change, moving to theatre, etc). These low levels of oxytocin during labour can cause contraction to slow down or stop altogether, PPH, leading to caregivers recommending unnecessary medical intervention. Interestingly, although the rise in adrenaline, which is a catecholamine, can negatively affect the release of oxytocin during the first stage labour, these catecholamines play a very important part in the second stage of labour, giving the mother the energy she needs to birth her baby. However, their levels drop quickly in the immediate postnatal period and keeping them low allows oxytocin to encourage bonding and prevent excessive bleeding.
In such cases, oxytocin can be used to induce birth or to augment a labor that is progressing slowly because of inadequate uterine contractions. The decision to induce has recently been on the rise for convenience or to accommodate busy schedules. However, according to the American College of Obstetricians and Gynecologists (ACOG), labor should be induced only when it is more risky for the baby to remain inside the mother's uterus than to be born. Induction of labor has increased from 9% to 18% of all U.S. deliveries in recent years and there are several useful oxytocin induction protocols are available (Stubbs, 2000). Higher-dose protocols tend to result in fewer cesarean deliveries for dystocia but more "fetal distress." Oxytocin's greatest weakness is that some patients will not respond well to it, especially with marked cervical unfavorability. However, given an individual patient whose uterus will respond adequately to this drug, oxytocin augmentation has the advantage of short half-life and the option for prompt cessation if desired. Oxytocics may be administered to stimulate uterine contraction thereby helping prevent hemorrhage.
The management of stimulation of labor with oxytocics has potential dangers in the prenatal and intrapartal periods. Oxytocin can present hazards to the mother and fetus which are primarily dose related, with most problems caused by high doses that are given rapidly. It is the primary health care provider who must write the order for the induction or augmentation of labor with oxytocin.
Without the introduction of inhibiting factors, oxytocin creates a positive feedback loop during labour and birth. As oxytocin is produced in the hypothalamus, released into the body via the pituitary gland, it stimulates uterine contractions, which, in turn, transmits a signal back to the hypothalamus to produce more oxytocin, and this process continues until the baby is born. Afterwards, the physical stimulation of the mother's nipples broadcast a signal to the hypothalamus in less than a second, causing neurons to release even more oxytocin, aiding the separation and birth of the placenta. Although putting the baby to the breast may be the easiest way to increase oxytocin levels in the immediate postnatal period, it is also important to enjoy skin-to-skin contact and eye gazing between mother and baby which also encourage the release of oxytocin. Hormonally speaking, labour and birth is a continual dialogue between the mother and her baby or babies.
As well as a rise in the levels of the hormone oxytocin in labour, the number of actual oxytocin receptors increases gradually as well - gradually throughout pregnancy, then sharply during labour as a result from increasing level of estrogen throughout the body. The rise of receptor concentration ensures that oxytocin can have the effect to help birth the baby at the very end of pregnancy. Oxytocin release peaks once again with the delivery of the placenta, assisted by the infant lactating and stimulating the nipples. Maternal oxytocin levels then dwindle over the next hour or so whereas newborn levels peak approximately half an hour after birth and remain elevated for at least four days. This period of time where both the mother and infant are under the influence of hormones, namely oxytocin, is known as "The Babymoon".
Because oxytocin is released during labor to stimulate uterine contractions, a woman in labor can also experience milk-ejection during labor since nursing is also stimulated by this hormone. This readies the breast for immediate feeding by the infant after birth. Oxytocin stimulates the let-down or milk-ejection reflex after birth in response to the infant sucking at the mother's breast. It is an essential hormone to lactation. As the nipple is stimulated by the suckling infant, the posterior pituitary is prompted by the hypothalamus to produce oxytocin (Lowdermilk & Perry, 2007). This hormone is responsible for the milk-ejection reflex. In a nursing mother, "the myoepithelial cells surrounding the alveoli respond to oxytocin by contracting and sending milk forward through the ducts to the nipple," (Lowdermilk & Perry, 2007). Milk-ejection reflex can be triggered by thoughts, sights, sounds or odours that the mother associates with her baby such as hearing her baby cry. Many women say they experience a "pins and needles" sensation in the breasts although milk-ejection can also occur during sexual activity because oxytocin is released during orgasm.
Oxytocin also has the important function of contracting the mother's uterus after birth to control postpartum bleeding and promote uterine involution (Lowdermilk & Perry, 2007). Thus mothers who breastfeed are at decreased risk for postpartum hemorrage. These uterine contractions or "afterpains" that occur with breastfeeding can be painful during and after feeding for the first 3 to 5 days.
Throughout the birthing process, oxytocin plays a central role in ensuring that reproduction occurs smoothly. From its release during sexual orgasm in both men and women to its aid in stimulation lactation, oxytocin is necessary for the reproduction cycle to continue. Upon its initial release during sexual activity which allows for bonding between a male and female to its release during breastfeeding which helps the mother feel close to the infant, this "hormone of love" helps in building relationships and emotional bonds. Physiologically it helps to contract the uterus which helps in the labor process and in preventing a slow labor which could be dangerous and even fatal to the fetus. After the infant has been born, it continues to contract the uterus which prevents hemorrhage and promotes uterine involution, safeguarding the mother from the potentially dangerous side effects of labor. Oxytocin is crucial in lactation and stimulating the nipples to contract. In every moment of the birthing process, the role of oxytocin can not be ignored. It is an important part of pregnancy and the path to mothering an infant.
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