During the first trimester, in week 3, the first missed period will occur, the brain and nervous system start to form, and the placenta acts as some vital organs (liver, lungs, kidneys) for the embryo, and is connected to the embryo by the umbilical cord. Soon after this, the embryo is approximately 6.4mm long, and the neural tube closes. In week 5, the heartbeat can be detected, and the embryo is the size of a small seed.
By the eighth week of pregnancy, the embryo contains 10,000 cells, and is 2.5cm long, and the startle reflex is developed. In week 12, the embryo reaches the foetal stage, all body parts are then present, though need development. The foetus is able to somersault, swallow, and suck at this stage, soft downy hair is forming on the foetus, the organs function, and the foetus is approximately 7.5cm long – this completes the development in the first trimester.
During the second trimester (weeks 14-27), the foetus continues to develop, during weeks 15 and 16 the baby starts to hear it’s first sounds, the genitals form, and a wax like substance called vernix covers the baby. By week 20, the baby weighs approximately 460g, it starts to use reflexes, and the bones harden. The baby also feels emotions at this stage, and dreams occur in it’s sleep. The baby is able to survive outside the womb at 24 weeks - despite the fact that the lungs are not fully formed - and it can also open it’s eyes for the first time. Towards the end of the second trimester, the baby weighs around 0.5kg, and is approximately 33cm long, and is very active, especially kicking.
The third and final trimester is the period of 28-40 weeks, this is when the foetus starts to grow very quickly, during the seventh month of pregnancy the baby weighs 1800g and is 40cm long, and becomes less active due to the fact that it is filling the space in the uterus so there is consequently less space for movement, such as somersaults. The baby’s developing brain can recognise the mother’s voice, and is able to process information and respond more quickly. A sleeping and waking pattern is starting to be developed at this stage.
During the eighth month of pregnancy, the baby continues it’s growth, by week 35 it weighs 2800g, and gains around 280g per week from this time. The head grows more than the rest of the body to allow for rapid brain growth, and the fine downy hair starts to disappear from the body. The baby now also swallows, urinates, and can make breathing movements. Glycogen forms in the baby’s liver which the baby uses, along with it’s fat reserves, during birth as a source of energy – it also helps while the baby is establishing a feeding pattern. The head usually engages in the pelvis at this time.
The final month of pregnancy (weeks 37-40) provides the final preparations and changes to both mother and baby’s bodies, the amniotic fluid reduces while the baby is growing to fill the space in the amniotic sac, and at 37 weeks, the baby weighs about 3kg, and is lying head down – birth will occur any time between weeks 38-42.
Developmental Influences
The lifestyle choices that a woman makes while trying to become pregnant is incredibly important for both her and the baby’s development, for instance, diet is a huge factor. In the first two months of pregnancy, consuming too much Vitamin A can increase the risk of the baby having a birth defect, and an all round balanced nutritional diet is essential to the baby’s development, supplements containing folic acid and Vitamin B are advised, as these help prevent neural tube defects, and lower the possibility of congenital abnormalities.
The amount of exercise undertaken before and during pregnancy is also a factor, as if the woman was not very active before pregnancy, suddenly taking up strenuous activity will exhaust her. Exercises that are recommended by the NHS include pelvic tilt exercises, abdominal strengthening exercises, and swimming. Contact sports aren’t recommended, as there is a chance of being hit, and horse riding is among one of the sports that is dangerous because of the risk of falling. Risks to the foetus include Hypoxemia, which can restrict blood supply to the foetus, Heart rate changes, Hyperthermia, and Extremes in Barometric pressure, which can again cause harmful increases in the foetal heart rate.
The age of the woman who is pregnant can make direct changes to how the baby will grow – if the mother is under 15 years old, there is an increased risk of an underweight baby, but if the mother is older than 35, there is a higher chance of diabetes, a miscarriage, a stillbirth, or a baby with chromosomal abnormalities. Both of these age groups also carry a higher risk of developing high blood pressure and pre-eclampsia, which occurs only during pregnancy and affects both mother and baby in 5-8% of pregnancies. It its main symptoms are high blood pressure and protein in the urine. Pre-eclampsia occurs after approximately 20 weeks of pregnancy, and these types of disorders during pregnancy result in 76,000 mother, and 500,000 infant deaths per year.
The risks associated with a woman over the age of 35 are similar to those experienced by a smoker – Nicotine constricts blood vessels reducing the blood flow and nutritional supply to the placenta, which runs the high risks of a low birth weight, a miscarriage, a stillbirth, or a premature baby.
Substance abuse also affects the development of the baby – recreational drugs can cause a low birth weight, congenital abnormalities, or premature birth. Babies can be born ‘addicted’ to drugs, all round development can be affected, and epilepsy is a possible result. Certain types of medication, such as chemotherapy can also cause congenital abnormalities, though even medicines such as Ibuprofen can stop blood clotting, increasing the risk of uncontrolled bleeding for both mother and child. Some drugs administered at birth can cause problems, for example, Pethidin makes the baby sleepy and slow to feed.
Alcohol consumption while pregnant causes the baby to be smaller, with a much smaller brain, and heavy drinkers face the increased risk of their baby being born with Foetal Alcohol Syndrome (FAS), which can cause facial and skeletal abnormalities, such as a very small head, and can cause the heart to malfunction. It has lasting effects, which can affect development and learning rates.
Foods that should be avoided throughout pregnancy
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o Soft and blue cheeses, such as camembert, brie and stilton
o All types of pate
o Potato salad and coleslaw
o Ready meals or reheated food
These are due to the high levels of listeria bacteria that are occasionally found in these foods – this can cause listeriosis, which is a flu-like illness that can cause stillbirth, miscarriages, or severe illness in babies.
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o Raw meat and poultry
o Unpasteurised milk
o Untreated water
o Raw eggs and raw egg products
These should be avoided due to the risk of campylobacter and salmonella, which can cause food poisoning, that may lead to a miscarriage.
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o Unwashed raw fruit and vegetables
o Raw/Undercooked meat
o Cured meats
o Unpasteurised goats’ milk or cheese
These can cause toxoplasmosis, which is an infection caused by a parasite that is found in cat faeces, raw meat, and vegetables with soil on them.
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o Liver
o Liver products, e.g. Pate
Too much Vitamin A can harm an unborn baby; no high dose multivitamins should be taken throughout pregnancy.
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o Shark, swordfish, and marlin – high mercury level can damage nervous system of unborn baby, and avoid shellfish, to reduce risk of food poisoning.
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It is important that a woman should avoid consuming more than 200mg of caffeine per day while pregnant, as the body absorbs iron differently when caffeine is an influence. High levels of caffeine can result in a baby with a low birth weight or a miscarriage. This means women should not consume more than two mugs of tea or five cans of cola or four chocolate bars. Flu and cold remedies also contain caffeine.