How do processes of prenatal development and birth go? - Chapter 4

What to know about prenatal development? 

Ovulation is when a follicle, developed in the ovary, erupts and releases an egg (ovum), supported by the follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Unfertilized, the egg leaves the body as menstruation from the uterus. But after intercourse, sperm can penetrate the egg cell and form a zygote. Infertility is when pregnancy doesn't come up after a year of trying and can have multiple causes, like sexually transmitted infections, problems with ovulation or sperm production, or endemetriosis (when bits of tissue lining the uterus grow outside the uterus). In some cases assisted reproductive technologies (ARTS) are sought, like articifial insemination or in vitro fertilization (IVF). 

Embryologists study early development and dividie prenatal development into three stages: 

• The germinal period which lasts approx. 2 weeks. It comprises the mitosis of the zygote. When the mass has 12-16 cells it's called a morula. During day 4-5 an inner cell mass forms, the entire mass is named the blastocyst. During day 6-7 the blastoycst attaches to the wall of the uturus. And during week 2, the blastocyst becomes fully embedded in the uterus wall, having about 250 cells.
• The embryonic period, from the the 3d to the 8th week. In week 3 the blastocyst is an embryo, and three layers emerge: the ectoderm, mesoderm and endoderm, which will turn into organ systems like the central nervous system, muscles, bones, heart and lungs. In week 5 the brain differentiaties into forebrain, midbrain and hindbrain. In rare cases the neural tube (needed indevelopment of the brain) fails to fully close, and this can at the bottom of the tube lead to spina bifida (when part of the spinal cord is not fully encased in the protective covering of the spinal column. Can lead to neurological problems). At the top of the tube it can lead to anencephaly (when the main portion of the brain above the brain stem does not develop well). Those neural tube defects are most common when a B vitamin called folate is lacking in the mother, e.g. through poor nutrition. In week 7-8 sexual differentiation starts: testes develop through testosterone and a hormone inhibiting female development, or ovaries when these hormones are absent. Every major organ thus takes shape in a process named organogenesis and by week 8 most structures are present. In this period the layers of the blastocyst have turned into structures: the outer layer turns into both the amnion (a membrane that fills with fluid and protects the embryo) and chorion (membrane surrounding the amnion and attaches villi to the uterine lining for gathering nourishment for the embryo). The chorion ultimately becomes the lining of the placenta (a tissue fed by blood vessels from the mom and connected to the embryo by the umbilical cord. Through this cord and the placenta the embyo gets oxygen and nutrients and eliminates carbon dioxide and wastes. The placental barrier allows these to pass through, but prevents the blood cells of embryo and mother from mingling, and protects from harmful substances).
• The fetal period, from the 9th week until birth. This is a critical period for brain development, involving three processes: - proliferation: neurons multiplying very fast, - migration: neurons moving from the center of the brain to particular locations in the brain, to specialize. Some passively (neurons for brain stem and thalamus), being pushed away, and some travel actively (neurons for cerebral cortex), - differentiation: neurons evolve into a certain fuction and communication with other neurons can start. When something goes wrong in those stages, the nervous system will not function well. During the second half of pregnancy neurons also develop an insulating cover named myelin which improves their skills of transmitting signals, and they organize in working groups for vision, memory etc. Moreover in this fetal period, the organs formed will continue to develop and start functioning. Also external sex organs appear and the fetus becomes very active, even yawning, playing and urinating. Actions later evolve into thumb sucking. By the end of the second trimester the sensory organs function. And at about 23 weeks, it is the age of viability and then the fetus has a little chance of surviving well outside the uterus (if developed well), but with just one more week the survival rate gets to 55%. 

What does the prental environment mean for the fetus?

From conception the interactions between person and environment begin and have their influence. And during prenatal period, internal factors like the mothers hormone levels as well as external factors like pollution exposure can alter the expression of genes throughout life (epigenetic effects). This is part of a process named fetal programming, which is about the environmental events/maternal conditions altering the expected genetic unfolding of the fetus. And the offspring of the unborn child can also be affected by this through epigenetic codings. 

A teratogen is any environmental thing (disease, drug e.g.) that can harm a developing fetus, and there is a small percent of fetuses that are significantly affected but it's still a present issue. A few things to know: 

• the effects of teratogens are worst during the critical period or also named sensitive period, when an organ grows quickest (during organogenesis).
• the greater the level/duration of exposure, the bigger chance of damage.
• genetic makeup of the child and the mother influence the susceptibility to harm from teratogens.
• the quality of both prenatal and postnatal environments determine teratogen effects as well.

Teratogen effects can be from:

• thalidomide, a mild tranquilizer used to relieve morning sickness in earlier years. However it caused deformed babies, different deformations depending on when the drug was taken. 
• tobacco, thus smoking. Effects may include increased risk of miscarriage, growth retardation, central nervous system impairment and later health problems. Also sudden infant death syndrome (SIDS) could occur, when a sleeping baby suddenly dies. These effects are created because smoking restricts blood flow to the fetus, reducing the levels of oxygen and nutrients. 
• alcohol. Prenatal alcohol disrupts neuronal migration, can lead to neuronal death and can impair the function of glial cells (cells needed to support and nourish neurons). The worst outcome is the fetal alcohol syndrome (FAS) resulting in among other things small, light kids, facional abnormalities, irritability, a lower IQ and central nervous system damage. Not all children with FAS also face problems in adulthood, so environment plays its part as well. Children exposed to prenatal alcohol but without FAS have problems labeled fetal alcohol effects or alcohol-related neurodevelopmental disorder. Father's drinking can also affecet the fetus, through either mutations of DNA passed on to the offspring or epigenetic effects. But it might also be a poor parenting style that influences the fetus, so more research is needed.
• cocaine. Can cause miscarriage or fetal strokes, can result in retarded growth and fetal malnourishment. At birth some babies face withdrawal-like symptoms, and deficits in information processing. Some consequences continue through adolescence. For persisting problems, it's unclear if they are caused by the prenatal cocaine or other risk factors that come with substance-abusing parents. 
• antidepressant drugs. Can cause heart malformations, neural tube defects and respiratory distress.
• marijuana. Heavy use has been connected to premature birth, behavioral abnormalities and low weight.

Diseases and infections can also cause problems: 

• rubella (German measles) can cause blindness, deafness, heart and intellectual problems. Now most women are immune to this disease.
• diabetes. In poorly controlled maternal diabetes, premature birth, miscarriage, heart problems and neural tube problems can come about. 
• STI's. Most worrying one is acquired immunodeficiency syndrome (AIDS), caused by the human immunodeficiency virus (HIV). AIDS destroys the immune system. Mothers with HIV can pass on the virus to their babies when the virus gets through the placenta, when at birth blood may be exchanged, or during breast-feeding. Treatment can minimize the risk that the virus is passed on. Another concerning STI is syphilis which can cause miscarriage. With treatment blindness, heart problems and brain damage can be prevented. The difference with rubella is that rubella damages most in the early stage and syphilis in the middle and final stages. Chlamydia can also cause problems but it's easily treatable. And gonorrhea damages the eyes during birth, eyedrops have to be administered. 
• Flu. Heavy flue can cause miscarriage or neural problems that can lead to decreased IQ.

And two environmental conditions can cause damage:

• radiation. After the atomic bomb dropping in 1945 it caused many pregnant women to lose their child or the infant to have intellectual disability and more chance at cancer. Neuron processes are disrupted. Even clinical use of radiation, like X-rays can be dangerous. 
• pollutants (like ozone, carbon monoxide and lead). Can cause prematurity, low birth weight, decreased cognitive abilities and psychomotor development problems. Mercury exposure which can come from eating certain fish can cause bad memory, language problems and attention problems. And pesticides or bisphenol-A (found in plastics) can cause problems. 

Young (probably through poverty and lack of good prenatal care) and old mothers have a bigger chance of stillbirth, the safest time to give birth is from age 20 to age 35. Women over 35 have a bigger chance of getting fraternal twins since they are likely to release more eggs at the same time. Older fathers also have more trouble creating healthy offspring, miscarriage risk increases with father's age as well and offspring can get heart problems, neural tube defects and preterm delivery. Down syndrome probability increases with the parents age increasing as well, however young fathers are at greater risk for offspring with Down too. And a father that has been exposed to environmental hazards can also pass this on through his sperm, and the same goes for smoking.

Lamaze method of prepared childbirth teaches women to associate childbirth with pleasant things and to prepare themselves for it (breathing exercises, relaxation techniques etc.)

When a mother experiences heavy emotional stress over a long time during her pregnancy and it affects daily life, it can be damaging, resulting in e.g. quick heart rate, stunted growth and premature birth, and after birth more crying and more active. Female babies seem to be more sensitive to this. Later in life depression and even schizophrenia are more probable. It seems prenatal exposure to stress hormones (cortisol) can alter the later stress response by fetal programming the nervous system differently. A quick scare can send adrenaline to the fetus, resulting in more motor activity, but is generally not damaging. A final point is that heavy preconception stress is related to higher rates of infant mortality. An emotional state like depression can also affect the baby, in ways of motor delays or preterm birth, by affecting the levels of neurotransmitters in mothers and their fetuses. Untreated depression can affect the baby, but depression medication as well.

Maternal malnutrition can cause problems with the spinal cord, less brain cells, stillbirth, difficulties with growth, and neural tube defects. Sometimes cognitive deficits are found in the child. A deficiency of folate/folic acid (B vitamin) can cause neural tube defects. Maternal obesity relates to offspring obesity and diabetes, and even paternal obesity relates.

What about the perinatal environment?

The perintal environment has everything to do with birth and labor. A perinatologist is a maternal-fetal specialist and is recommended for problematic, complicated pregnancies/deliveries, but women have a lot of choices when it comes to who they want around in their labor period, like midwives or physicians. They can also call for a doula (someone trained to provide support throughout childbirth) which has positive effects. Childbirth contains three stages. Firstly, the mom feels contractions of the uterus. This stage ends when the cervix has fully dilated to 10 cm, so the baby's head can come through. Some women take oxytocin, this is a hormone that can initiate and speed up the contractions. The second stage is delivery and starts with the fetus's head going through the cervix into the vagina, and it ends when the baby emerges from the body. In this stage the mom needs to push. And the third stage is the delivery of the placenta. 

What are possible hazards?

• Anoxia or in other words a lack of oxygen. This can result from a tangled umbilical cord, sedatives given to the mom reaching the fetus, or because of breech presentation (when the feet or buttocks are coming first and cesarean section is needed). Anoxia can initially lead to heart rate problems and breathing difficulties, and in the long run severe anoxia can cause memory problems or cerebral palsy (a neurological disability that results in problems with muscle movements and increases risks of intellectual and speech disabilities). 
• Complicated delivery, when assistance is needed, such as vacuum extraction (suction), a procedure in favor of using forceps (instrument that looks like salad tongs), or cesarean sections. Those assistance techniques can bring extra risks or consequences and sometimes they are used too prematurely and a normal delivery would have been possible.
• Medications, such as sedatives for relaxation, analgesics/anesthetics to reduce pain and stimulants to help the contractions. Some drugs can pass the placenta which influences the baby.

What factors influence a mother's experience of labor? Firstly, longer labor times create more negative feelings about giving birth. Psychological aspects of the mother matter as well, like attitude, expectations and sense of control. Moreover, social support has influence on the experience. Culture plays a part in the experience and practice of labor too.

After birth a bit of "baby blues"  can occur, a mild mood of being irritiable, emotional and sad, probably coming from a drop of the level of female hormones. A more serious condition, faced by approx. 15-20 % of new mothers, is named postpartum depression, which is clinical depression lasting 2 or more weeks. This usually happens to women who had emotional problems before or who lack social support. This depression has loads of influence on the child-mother bond and the child itself. 

Fathers can experience symptoms called couvade (they experience the same physiological symptoms as their pregnant partner), like weight gain, insomnia and nausea, possibly through a shift in hormones.

How about the neonatal environment?

The neonatal environment is the month after birth. This has to do with, for instance, breast-feeding, which has many different advantages over bottles, such as featuring substances that protect babies from infections, stronger lung function, cognitive advances during infancy and better immune systems. Again, culture is very influential in many ways in the neonatal environment, for instance through social attitudes on breast-feeding.

Newborns are routinely screened with the Apgar test, providing an assessment of for instance heart rate, reflexes and respiration. This test shows which infants are extra vulnerable and might need extra medical care. Take for instance low birth weight babies (LBW), whose survival and health is of concern and who usually face long-term disabilities if they survive, such as poor academic achievement, blindness, autism and respiratory difficulties (because of lacking a substance named surfactant which aids breathing). Most fragile are micropreemies, babies weighing less than 800 grams at birth. LBW babies can be related to among others the age of the mother, the SES of the mother, race, stress, tobacco or alcohol use, pregnancies with more fetuses and infections. LBW babies can be helped through breast milk, skin-to-skin contact like laying on the chest (referred to sometimes as kangaroo care) and massage therapy. Congenital malformations are other defects that are present at birth, such as herat defects, spina bifida and Down syndrome.

So how can postnatal life make up for harm in the prenatal or perinatal period? What makes it that some children whose mother drank alcohol are eventually not affected by it and others are? Can babies exposed to risks recover from this in later life? It seems that they are quite resilient and can sometimes overcome these things through a good environment. There are 2 protective factors at work then: personal resources  (having qualities like intelligence or sociability that help them create more stimulating environments) and a supportive postnatal environment.