A woman ordinarily has two tubes and two ovaries, one at each side
of her uterus. Every month one of the ovaries in turn releases an egg
(ovum) which passes slowly along the tube towards the womb cavity
If
the egg is not fertilised within 12 hours or so of being released, it
dies; it cannot develop further.
But if the woman has sexual intercourse during the days of her monthly
cycle just before or at the time when an egg has been released from the
ovary, then many sperm cells released by her partner may travel up to
the Fallopian tube and one may fertilise the egg. When fertilisation is
completed and the nuclei of egg and sperm have combined, a new being
comes into existence and is capable of further development. Because the
parents are human - belonging to the species Homo sapiens - the new
being is also human. Fertilisation (by which we mean conception) marks
the beginning of the human lifespan.
A consultant specialising in the care of pregnant women writes: "Life does not begin with birth. When born, we are already nine months old... we have a responsibility to learn how to study the life in utero, and how to care for it"1
Rarely, one embryo splits into two and both cells develop separately, as identical twins, similar in appearance.
"They have the same genetic make-up and apparently the whole genetic message is the same in both of them. Nevertheless, they are obviously different human beings."2
After
fertilisation the single cell splits into two, then the two cells
double to four, four to eight, eight to sixteen and so on. Because the
cell cluster looks superficially like a berry it is called the morula
(Latin for "mulberry"), but the new life is always biologically human
(species Homo sapiens).
The journey along the Fallopian tube continues slowly for about
four days. Growth increases. By the time the womb cavity is reached,
the cell cluster becomes hollow and fluid-filled, and is referred to as
the blastocyst. However,
this is not an inert clump of cells but a busily developing human
individual: differentiation (organisation into different parts and
functions) is already taking place. Meanwhile the uterus is forming a
spongy lining within which the embryo will implant. To achieve this the
embryo burrows into the wall of the womb and is covered over by the
lining of the womb. This begins 6 days after fertilisation and is
completed within the next 7 days.
If fertilisation has not taken place, the lining of the uterus comes away at the end of the monthly cycle as the woman's menstrual period. But once implantation occurs, the embryo sends out a hormonal signal which prevents the mother's period. This is usually her first indication of pregnancy.
The baby is connected to the placenta by the umbilical cord, the lifeline channelling nourishment in and taking wastes out, which will be cut close to the baby's abdomen at birth and will leave the mark of the navel. During pregnancy the baby obtains oxygen from the mother's blood via cord and placenta, so does not drown in the surrounding fluid.
By 25 days from fertilisation the body is developing. Head and
trunk appear and tiny arm buds begin to form, followed by leg buds. The
early embryo seems to have a
"tail", but this is really a protective covering for the spinal cord.
Because the central nervous system (brain. spine and spinal cord) is so
important, governing sensory and motor functions, the embryo's body is
designed for rapid growth of head and back.By 21 to 25 days the baby's heart is beating. Other internal organs
are present in simple form and functioning as they grow. Early facial
features appear. The doctor who performed the first-ever blood
transfusion to an unborn baby has described the embryo at the end of
the first month from fertilisation:

"By 30 days, just two weeks past mother's first missed
period, the baby - one quarter of an inch long - has a brain of
unmistakable human proportions, eyes, ears, mouth, kidneys, liver, an
umbilical cord and a heart pumping blood he has made himself."3
The embryo increases in size from 5mm at four weeks to 4Omm by the end of the eighth week. The baby in the womb is usually measured from the top of the head to the bottom of the spine (crown-rump lengths).
By the sixth week from fertilisation tiny fingers appear, followed
within days by the toes. By the seventh week the baby has individual
fingerprints; no two sets of fingerprints are ever the same. Even in
utero the baby has unique characteristics.The ears continue to develop: by seven weeks the outer ear is present, and the inner ear, with its hearing and balancing mechanisms, is well established (see page 15 'Hearing')
"By 45 days, about the time of the mother's second missed period, the baby's skeleton is complete in cartilage, not bone, at first; ... he makes the first movements of his body and new-grown limbs, although it will be another 12 weeks before his movements are strong enough to be transmitted through the insensitive uterus to be detected by the mother's sensitive abdominal wall."4
Human embryos of five weeks gestational age have
been seen to move away from an object touching the mouth area. The
sensitive area extends to include the rest of the face in the sixth and
seventh weeks and the palms of the hands and soles of the feet in the
eighth and ninth weeks respectively.6 "Nine weeks after conception the baby is well enough formed to bend his fingers round an object in the palm of his hand. In response to a touch on the sole of his foot he will curl his toes or bend his hips and knees to move away from the touching object. At 12 weeks he can close his fingers and thumb and he will open his mouth in response to pressure applied at the base of his thumb."8
From a simple, generalised response to stimulation at 6 weeks gestational age, the foetus develops an almost complete range of responses to touches on the skin by 12 weeks.9
Brain cells which are essential for consciousness in the adult are
known to be present in the foetus by 10 weeks. Nerve fibres which
transmit pain impulses are known to be present before fibres inhibiting
pain are completed.
According to a scholarly study of the available evidence, this
"implies that the first trimester foetus may be more susceptible to
pain than slightly older subjects."10. The first trimester of pregnancy is the first three months.
In other words, if the baby can experience pain before the
body's mechanisms to suppress pain have developed, this means that the
baby may be able to feel pain at a much earlier stage than was
previously thought, and perhaps even more keenly in the first three
months of pregnancy than later.
The same study concludes that there is a likelihood that the
"foetus has started to acquire a sentient capacity perhaps as early as six weeks, certainly by nine to ten weeks of gestation. Anatomical examination of such foetuses indicates the probability that differentiation sufficient for reception, transmission and perception of primitive pain sensation has already occurred."11
Foetal breathing movements have been detected as early as 11 weeks 14. Although the baby does not breathe air inside the fluid-filled
amnion, these movements help develop the respiratory organs.
The authors of a textbook on the unborn which is used in medical
schools world-wide explain why the foetus can hear while immersed in
fluid:
"The ears of the foetus function as early as the fourth month, and there is evidence that it hears a good deal. One might object that if a person dives under water and someone else talks to him he hears only a muffled sound. This is true. The sound is muffled by the cushion of air remaining in the auditory canal outside the ear drum. But the foetus living in the amniotic fluid has no muffling air cushions around its ear drum - and water conducts sound better than air does. The silent world of the foetus (or, below the surface of the ocean) is a fantasy, unfounded in reality."16
The baby hears sounds from the outside world as well as from the mothers heart and digestive system: "In fact the inner ear of the foetus is completely developed by mid-pregnancy, and the foetus responds to a wide variety of sounds. He is surrounded by a constant very loud noise in the uterus - the rhythmical sound of the uterine blood supply punctuated by the noises of air passing through the mother's intestine. Loud noises from outside the uterus such as the slamming of a door or loud music reach the foetus and he reacts to them."17 Tests using different types of music indicate that the baby even appears to have preferences: "A four- or five-month-old foetus definitely responds to sound and melody - and responds in very discriminating ways. Put Vivaldi on the record player and even the most agitated baby relaxes ... In a film made at the City of London Maternity Hospital, Yehudi Menuhin demonstrated that it was possible to contact the unborn via music."18 Babies learn to recognise their mothers' voices whilst in the womb 19 and even to recognise stories which are read to them in the womb.20 Newborn babies whose mothers watched Neighbours during pregnancy have been seen to stop crying and become alert when they hear the theme tune after birth.21
"It is very easy to demonstrate now with ultrasound that the babies make the most of all the space and room available to them ... We know that foetal comfort determines foetal position, that changes in maternal position provoke baby to seek a new position of comfort."26
These percentages had increased from previous years. With advances in technology and in understanding of human foetal development, premature babies' chances of survival are improving.
These figures refer to the length of the pregnancy from the
time of the mother's last menstrual period. and not to the age of the
baby from fertilisation. which would usually be two weeks less. (see
'Estimating length of pregnancy', section 1, above)
The mother's labour begins as (following hormonal signals including
that from the placenta) the muscular uterus contracts to expel the
baby. The cervix (neck of the womb) gradually opens to allow the baby
to pass into the vagina (birth canal). The amnion tears and releases
its fluid (this is often referred to as "the waters breaking").
Contractions become more frequent as the baby is pushed through the
cervix and vagina. If the mother has attended ante-natal classes she
will have learned what to expect and how to control her breathing and
pushing process. A midwife and/or a doctor supervises the mother and
baby during labour. The baby's father may wish to be present to lend
support and encouragement and to see his baby from the moment of birth.
After labour, which varies in length but usually lasts some
hours, the baby is born. A gasp and a cry start the lungs working. The
umbilical cord is cut and the baby is examined and weighed. Normal
birthweight is approximately 3,400 grammes or about 7½ lb, but
considerable variations sometimes occur because of genetic factors,
health problems and outside influences such as the mother's smoking
during pregnancy.
Finally the membranes and placenta are expelled. The baby no longer needs a direct life support system as he or she can now breathe air and take milk.
The doctor should know about a pregnancy as early as possible so
that any medicines he prescribes are safe for both his patients. This
is particularly important as the pregnancy may, of itself, cause
symptoms such as headaches and fatigue for which the mother may seek
medical treatment. If the mother has "morning sickness", caused by
normal hormonal responses to pregnancy, a harmless antacid can be
given. Tablets of iron and folic acid (a B vitamin) are routinely
prescribed to prevent anaemia: it is safe and important to take these.
Pregnancy can also lead to an increased sense of well-being and
contentment. Many women find that their complexions improve and they
feel more relaxed as a result of the hormonal changes in their bodies.
During pregnancy the mother should attend her doctor's
ante-natal clinic for regular checks on her weight and blood pressure,
and on her baby's heartbeat, growth and position in the uterus.
Arrangements will be made for the baby's birth at home or (more likely)
in hospital. Mother and perhaps father may also attend parentcraft
classes: there they will learn how the baby develops, how to care for
mother and child before and after birth, and how to cope with the
process of birth itself.
The mother does not need to "eat for two" in the sense of
increasing her food intake. Adequate amounts of protein, vegetables,
fruit and milk should be taken (particularly milk, since the mother
needs to replace the calcium taken from her system to make the baby's
bones). The doctor will advise on any special dietary needs. During
pregnancy a mother can expect to gain around 12kg (allowing for baby.
placenta, fluid and her own physical changes), but weight gain should
not be excessive and too much carbohydrate should be avoided.
Foetal breathing movements are substantially decreased if the
mother smokes cigarettes during pregnancy. There is evidence that
prematurity, stillbirth and slower development may be related to this
practice.29 It is important not to smoke during pregnancy or when near a pregnant woman.
Even moderate amounts of alcohol taken in early pregnancy may affect the child's growth and development (including that of the brain); heavy drinking carries a still higher risk.30 During the first three months of pregnancy the developing baby may be harmed by certain infections and drugs. For example, rubella (German measles) may damage the baby's heart, eyes or ears if the mother contracts it in early pregnancy. Such harm can be prevented by receiving immunisation against rubella as a small child or as a schoolgirl, long before pregnancy occurs. However, by the end of the third month the baby is less likely to develop a disability because the body is well developed.
| amnion | the fluid-filled membrane enclosing the baby in the womb. |
| ante-natal | before birth. |
| blastocyst (Greek, "sprout pouch') | the hollow, fluid-filled ball of cells which is the developing embryo at one week after fertilisation. |
| cervix | neck of the womb. |
| chorion | the outer capsule containing amnion, fluid and baby within the womb. |
| chromosome | part of a cell nucleus, made of DNA, carrying the genes; each species of animal and plant has a characteristic number of chromosomes per cell, except in reproductive cells which have only half that number to allow for their combination at fertilisation. |
| differentiation | development of cells to perform specialised functions (making nerves, bones, organs etc.). |
| DNA (deoxyribonucleic acid) | threadlike molecule in the nucleus of a living cell which can reproduce itself and transmit hereditary characteristics. |
| EEG (electroencephalograph) | an instrument which detects and records brain activity. |
| embryo (Greek, "to teem within") | stage of human development during the first eight weeks after fertilisation. |
| fallopian tubes | two tubes, one on each side of the womb, connecting it with the ovaries; fertilisation normally takes place in one of the Fallopian tubes. |
| the joining of sperm with ovum, completed when their nuclei are combined, to make a genetically new individual. | |
| foetus (Latin, 'young, offspring') | the developing human from eight weeks after fertilisation up to birth. |
| fraternal twins | twins who do not look alike because they develop from two different eggs and sperm cells. |
| full-time delivery | birth of a baby after a completed nine-month pregnancy (i.e. not a premature birth). |
| fundus | the top part of the womb, lying between the Fallopian tubes, which expands upwards as pregnancy advances and enables the doctor to assess the length of pregnancy. |
| gamete (Greek, "marriage partner") | reproductive cell; egg or sperm. |
| gene | a factor controlling inheritance of one particular characteristic (e.g. brown eyes). |
| gestational age | the baby's age calculated by estimating pregnancy as starting from the first day of the mother's last menstrual period. |
| hormone | substance produced by an organ or a gland which influences other organs or the whole body. |
| homo sapiens (Latin, "thinking man") | the human species. |
| identical twins | twins who look alike because they result from one egg and sperm when the zygote splits into two separately developing cells. |
| labour | the process of expelling baby, membranes and placenta from the womb. |
| morula (Latin, "mulberry") | the earliest stage of human embryo development; the first four days of life when the growing cell cluster looks like (but is not) a berry. |
| ovary | the egg-producing organ; normally a woman has two ovaries which take turns to release one egg per month. |
| ovum | egg (plural ova). |
| placenta | a temporary organ within the uterus which transfers nourishment and oxygen from the mother, removes waste products from the baby, and makes hormones to maintain and end pregnancy. Expelled after the baby is born, it is then also known as the "afterbirth". |
| post-natal | after birth. |
| prematurity | the baby is born before 37 completed weeks since the mothers last period and needs special care. |
| sentient capacity | the ability to feel sensations such as pain. |
| stillbirth | the baby is born dead. |
| trimester | a three month period of pregnancy. The first trimester covers the first to the third months; the second trimester the fourth to the sixth months; and the third trimester the seventh to the ninth months. |
| ultrasound | a technique for viewing the unborn child: high-frequency sound waves directed through the mothers abdomen send back signals which are converted to images on a screen. |
| umbilical cord | a temporary lifeline connecting the unborn child with the placenta, channelling nourishment from the mother and removing wastes from the baby. |
| uterus | the womb; in utero (Latin) in the womb. |
| vagina | the birth canal. |
| vernix | a greasy coating protecting the unborn baby's skin from prolonged contact with the fluid in the amnion. |
| zygote (Greek, 'joining') | the new, one-celled being formed when sperm fertilises egg; the zygote of the species Homo sapiens is a human being at the earliest stage of life. |