From a fetal perspective, the process of birth is a crisis. In the womb, the fetus was snuggled in a soft, warm, dark, and quiet world. The placenta provided nutrition and oxygen continuously. Suddenly, the contractions of labor and vaginal childbirth forcibly squeeze the fetus through the birth canal, limiting oxygenated blood flow during contractions and shifting the skull bones to accommodate the small space. After birth, the newborn’s system must make drastic adjustments to a world that is colder, brighter, and louder, and where he or she will experience hunger and thirst. The neonatal period (neo- = “new”; -natal = “birth”) spans the first to the thirtieth day of life outside of the uterus.
Although the fetus “practices” breathing by inhaling amniotic fluid in utero, there is no air in the uterus and thus no true opportunity to breathe. (There is also no need to breathe because the placenta supplies the fetus with all the oxygenated blood it needs.) During gestation, the partially collapsed lungs are filled with amniotic fluid and exhibit very little metabolic activity. Several factors stimulate newborns to take their first breath at birth. First, labor contractions temporarily constrict umbilical blood vessels, reducing oxygenated blood flow to the fetus and elevating carbon dioxide levels in the blood. High carbon dioxide levels cause acidosis and stimulate the respiratory center in the brain, triggering the newborn to take a breath.
The first breath typically is taken within 10 seconds of birth, after mucus is aspirated from the infant’s mouth and nose. The first breaths inflate the lungs to nearly full capacity and dramatically decrease lung pressure and resistance to blood flow, causing a major circulatory reconfiguration. Pulmonary alveoli open, and alveolar capillaries fill with blood. Amniotic fluid in the lungs drains or is absorbed, and the lungs immediately take over the task of the placenta, exchanging carbon dioxide for oxygen by the process of respiration.
The process of clamping and cutting the umbilical cord collapses the umbilical blood vessels. In the absence of medical assistance, this occlusion would occur naturally within 20 minutes of birth because the Wharton’s jelly within the umbilical cord would swell in response to the lower temperature outside of the mother’s body, and the blood vessels would constrict. Natural occlusion has occurred when the umbilical cord is no longer pulsating. For the most part, the collapsed vessels atrophy and become fibrotic remnants, existing in the mature circulatory system as ligaments of the abdominal wall and liver. The ductus venosus degenerates to become the ligamentum venosum beneath the liver. Only the proximal sections of the two umbilical arteries remain functional, taking on the role of supplying blood to the upper part of the bladder.
A newborn’s circulatory system reconfigures immediately after birth. The three fetal shunts have been closed permanently, facilitating blood flow to the liver and lungs.
The newborn’s first breath is vital to initiate the transition from the fetal to the neonatal circulatory pattern. Inflation of the lungs decreases blood pressure throughout the pulmonary system, as well as in the right atrium and ventricle. In response to this pressure change, the flow of blood temporarily reverses direction through the foramen ovale, moving from the left to the right atrium, and blocking the shunt with two flaps of tissue. Within 1 year, the tissue flaps usually fuse over the shunt, turning the foramen ovale into the fossa ovalis. The ductus arteriosus constricts as a result of increased oxygen concentration, and becomes the ligamentum arteriosum. Closing of the ductus arteriosus ensures that all blood pumped to the pulmonary circuit will be oxygenated by the newly functional neonatal lungs
The fetus floats in warm amniotic fluid that is maintained at a temperature of approximately 98.6°F with very little fluctuation. Birth exposes newborns to a cooler environment in which they have to regulate their own body temperature. Newborns have a higher ratio of surface area to volume than adults. This means that their body has less volume throughout which to produce heat, and more surface area from which to lose heat. As a result, newborns produce heat more slowly and lose it more quickly. Newborns also have immature musculature that limits their ability to generate heat by shivering. Moreover, their nervous systems are underdeveloped, so they cannot quickly constrict superficial blood vessels in response to cold. They also have little subcutaneous fat for insulation. All these factors make it harder for newborns to maintain their body temperature.
Newborns, however, do have a special method for generating heat: nonshivering thermogenesis, which involves the breakdown of brown adipose tissue, or brown fat, which is distributed over the back, chest, and shoulders. Brown fat differs from the more familiar white fat in two ways:
- It is highly vascularized. This allows for faster delivery of oxygen, which leads to faster cellular respiration.
- It is packed with a special type of mitochondria that are able to engage in cellular respiration reactions that produce less ATP and more heat than standard cellular respiration reactions.
The breakdown of brown fat occurs automatically upon exposure to cold, so it is an important heat regulator in newborns. During fetal development, the placenta secretes inhibitors that prevent metabolism of brown adipose fat and promote its accumulation in preparation for birth.
Gastrointestinal and Urinary Adjustments
In adults, the gastrointestinal tract harbors bacterial flora—trillions of bacteria that aid in digestion, produce vitamins, and protect from the invasion or replication of pathogens. In stark contrast, the fetal intestine is sterile. The first consumption of breast milk or formula floods the neonatal gastrointestinal tract with beneficial bacteria that begin to establish the bacterial flora.
The fetal kidneys filter blood and produce urine, but the neonatal kidneys are still immature and inefficient at concentrating urine. Therefore, newborns produce very dilute urine, making it particularly important for infants to obtain sufficient fluids from breast milk or formula. (37)
APGAR Score: Newborn Assessment
In the minutes following birth, a newborn must undergo dramatic systemic changes to be able to survive outside the womb. An obstetrician, midwife, or nurse can estimate how well a newborn is doing by obtaining an APGAR score. The Apgar score was introduced in 1952 by anesthesiologist Dr. Virginia Apgar as a method to assess the effects on the newborn of anesthesia given to the laboring mother. Healthcare providers now use it to assess the general wellbeing of the newborn, whether or not analgesics or anesthetics were used.
Five criteria are assessed:
- Skin color
- Heart rate
- Muscle tone
Each criterion is assigned a score of 0, 1, or 2. Scores are taken at 1 minute after birth and again at 5 minutes after birth. Each time that scores are taken, the five scores are added together. High scores (out of a possible 10) indicate the baby has made the transition from the womb well, whereas lower scores indicate that the baby may be in distress. The technique for determining an APGAR score is quick and easy, painless for the newborn, and does not require any instruments except for a stethoscope.
Of the five APGAR criteria, heart rate and respiration are the most critical. Poor scores for either of these measurements may indicate the need for immediate medical attention to resuscitate or stabilize the newborn. In general, any score lower than 7 at the 5-minute mark indicates that medical assistance may be needed. A total score below 5 indicates an emergency situation. Normally, a newborn will get an intermediate score of 1 for some of the APGAR criteria and will progress to a 2 by the 5-minute assessment. Scores of 8 or above are normal.
The first breath a newborn takes at birth inflates the lungs and dramatically alters the circulatory system, closing the three shunts that directed oxygenated blood away from the lungs and liver during fetal life. Clamping and cutting the umbilical cord collapses the three umbilical blood vessels. The proximal umbilical arteries remain a part of the circulatory system, whereas the distal umbilical arteries and the umbilical vein become fibrotic. The newborn keeps warm by breaking down brown adipose tissue in the process of nonshivering thermogenesis. The first consumption of breast milk or formula floods the newborn’s sterile gastrointestinal tract with beneficial bacteria that eventually establish themselves as the bacterial flora, which aid in digestion. (37)
The Postpartum Period
As the saying goes, it takes nine months for the baby to grow, so it is going to take time for a woman’s body to recover after birth. We live in a culture where movie and music stars give birth and show off their flat stomachs within days. This is so unfortunate as it places pressure on all American women to do the same. The information in this section provides realistic information regarding the postpartum period. (1)
The first few days at home after having a baby are a time for rest and recovery — physically and emotionally. A woman needs to focus her energy on herself and on getting to know her new baby. Even though she may be very excited and have requests for lots of visits from family and friends, she should try to limit visitors and get as much rest as possible. Women should not expect to keep their house perfect. New moms often find that all they can do is eat, sleep, and care for their baby. And that is perfectly okay. New moms should try to lie down or nap while the baby naps. They should allow others to help and not be afraid to ask for help with cleaning, laundry, meals, or with caring for the baby.
Here is a list of common physical changes and experiences that occur after birth:
- There is a vaginal discharge called lochia. It is the tissue and blood that lined the uterus during pregnancy.
- It is heavy and bright red at first, becoming lighter in flow and color until it goes aware after a few weeks.
- There may be swelling in the legs and feet.
- Constipation may be experienced.
- Menstrual-like cramping is common, especially if the woman is breastfeeding. The breast milk comes in within three to six days after delivery.
The woman’s doctor checks a woman’s recovery at a postpartum visit, about six weeks after birth. Some women develop thyroid problems in the first year after giving birth. This is called postpartum thyroiditis. It often begins with overactive thyroid, which lasts two to four months. Most women then develop symptoms of an underactive thyroid, which can last up to a year. Thyroid problems are easy to overlook, as many symptoms, such as fatigue, sleep problems, low energy, and changes in weight, are common after having a baby. In most cases, thyroid function returns to normal as the thyroid heals. But some women develop permanent underactive thyroid disease, called Hashimoto’s disease, and need lifelong treatment.
Regaining a Healthy Weight
Both pregnancy and labor can affect a woman’s body. After giving birth, women lose about 10 pounds right away and a little more as body fluid levels decrease. Women should not expect or try to lose additional pregnancy weight right away. Gradual weight loss over several months is the safest way, especially if breastfeeding. Nursing mothers can safely lose a moderate amount of weight without affecting their milk supply or their babies’ growth.
Baby Blues and Postpartum Depression
After childbirth, women may feel sad, weepy, and overwhelmed for a few days. Many new mothers have the “baby blues” after giving birth. Changing hormones, anxiety about caring for the baby, and lack of sleep, all affect emotions. These feelings are normal and usually go away quickly. But if sadness lasts more than two weeks, the new mother should see her doctor. She may have a serious but treatable condition called postpartum depression. Postpartum depression can happen any time within the first year after birth.
Signs of postpartum depression include:
- Feeling restless or irritable
- Feeling sad, depressed, or crying a lot
- Having no energy
- Having headaches, chest pains, heart palpitations (the heart being fast and feeling like it is skipping beats) numbness, or hyperventilation (fast and shallow breathing)
- Not being able to sleep, being very tired, or both
- Not being able to eat and weight loss
- Overeating and weight gain
- Trouble focusing, remembering, or making decisions
- Being overly worried about the baby
- Not having any interest in the baby
- Feeling worthless and guilty
- Having no interest or getting no pleasure from activities like sex and socializing
- Thoughts of harming your baby or yourself
Some women don’t tell anyone about their symptoms because they feel embarrassed or guilty about having these feelings at a time when they think they should be happy. Postpartum depression can make it hard to take care of the baby. Infants with mothers with postpartum depression can have delays in learning how to talk. They can have problems with emotional bonding. Therapy and/or medicine can treat postpartum depression.
Emerging research suggests that 1 in 10 new fathers may experience depression during or after pregnancy. Although more research is needed, having depression may make it harder to be a good father and perhaps affect the baby’s development. Having depression may also be related to a mother’s depression. New fathers with emotional problems or symptoms of depression should talk to their doctors. Depression is a treatable illness. (38)
In this module, we learned about the amazing journey from conception to birth. Genetics lays the foundation for this journey. We inherit half of our genes from our mother and half from our father, except for the DNA in our mitochondria. That DNA comes only from our mother. Our genes interact with our environment to shape our development throughout our entire life. We learned that both prenatal development and birth occur in three stages. We also examined the physical adjustments that both baby and mother face after birth. In the next module, we will learn about physical development from birth through adolescence. (1)