Human development from conception to birth
Fertilisation
Every human being begins life as a single cell, formed when father's
sperm fertilises mother's egg. Fertilisation normally takes place in
the mother's Fallopian tube, which connects the uterus (womb) with the
ovary. The uterus is the size and shape of a large pear: it is made of
muscle and it stretches to allow the baby's growth throughout the
months of pregnancy.
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
Heredity
The cells of living beings contain DNA (deoxyribonucleic acid), the
substance in the nucleus that enable cells to reproduce and transmit
characteristics from generation to generation. When cells divide, the
DNA takes the form of chromosomes - the units carrying the genes that
pass hereditary features from parents to offspring. Different species
have varying numbers of chromosomes per cell: for example, a mouse has
40 while a cat has 38. Human body cells normally contain 46
distinctively human chromosomes. But an egg and a sperm cell contain
only 23 chromosomes each, to allow for their adding together at
fertilisation: sperm and ovum are termed gametes (from a Greek word for
"marriage partners"). When they "marry" they make one completely new
cell - the human embryo, zygote or conceptus - with 46 chromosomes
carrying a fresh, unique combination of genes. At fertilisation this
human embryo is about 0.1mm in diameter. Since characteristics come
from both parents the zygote is never the same as, or part of, the
mother, but is a genetically distinct individual. The colouring of
hair, skin and eyes, the sex of the new human being, and factors
influencing height and build, are determined at fertilisation by
information on the DNA.
Gender
A baby's sex is determined at fertilisation. A chromosome from the
father's sperm determines whether the child is male or female. If an X
chromosome is present the baby is a girl; if a Y chromosome is carried
by the sperm instead, the baby is a boy.
Twins
Occasionally two eggs are released by the ovary and fertilised.
This results in fraternal twins who are different in appearance and may
be of different sexes because their genes form from two eggs and two
sperm cells.
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
Blueprint, builder and house
The embryo is not simply a set of instructions for making a new human
being, like a blueprint for building a house. A blueprint is inert and
cannot carry out instructions, but the embryo is active and begins work
at once. A house needs builders, carpenters, electricians and plumbers
to complete it; but the embryo has the ability to grow spontaneously,
moving on to other phases of development and constructing the skeleton,
flesh, nerve connections and a waste disposal system of the human body.
After a house is built, a blueprint remains separate; but the embryo -
already an essential human by virtue of the genes - is blueprint,
builder and "house" together.
Implantation
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.
Estimating length of pregnancy
Generally a woman does not know the exact date of her baby's
conception. When she misses a period she may take a pregnancy test; she
should see a doctor promptly to obtain professional care for herself
and her child. The doctor takes the date of the first day of the
mother's last menstrual period as the starting-point for a 40-week
pregnancy. This gives the baby's gestational age. However since
fertilisation only occurs when the ovum is released from the ovary,
some two weeks from the beginning of the last period, the baby's actual
(conceptional) age is also two weeks less. Full-time delivery occurs 38
weeks after fertilisation, but 40 weeks after the mother's last
menstrual period. (In this booklet all developments of the embryo and
foetus are dated from the time of conception, or fertilisation unless
stated otherwise.)
Protection and life support
During and after implantation the embryo develops a protective,
fluid-filled capsule which surrounds and cushions the developing body
to prevent injury. Embryo and fluid are enclosed in two membranes, an
inner amnion and an outer chorion. The chorion is covered in rootlike
tufts, some of which form the early placenta - an organ made by the
baby and the mother which transfers nutrients from the mother's
bloodstream and removes waste products from the child's, though
mother's and baby's circulatory systems remain separate. The placenta
also produces hormones to maintain the pregnancy. In the ninth month it
will alter the mother's hormonal balance and triggers off the birth
process - although we are still unsure what causes labour to begin.
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.
Body development
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
Growing
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).
Hands and feet
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.
Eyes and ears
By six weeks the eyes which appeared in simple form in the first month develop lens and retina; the eyelids start to take shape.
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')
Movements
Spontaneous movements begin at seven weeks:
"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
Brain function
Brain waves have been recorded by EEG (electro- encephalograph) in the human embryo 40 days after fertilisation.
5
Response to touch
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
A British study shows that the baby's movements begin at the same
time as sensory nerves begin to grow into the spinal cord in the second
month of pregnancy; the nerve fibres respond to touches to the skin and
movement of the limbs: at this stage the baby's sensory nerves "appear
to be more sensitive than those of the adult or newborn baby."
7
From embryo to foetus
Around eight weeks the baby's cartilage skeleton begins to turn
into bone. The body is essentially complete. Now the baby can be
referred to as the foetus - a Latin term meaning "young, offspring."
Latin- or Greek-derived names are given to human beings at successive
phases of development, e.g. "zygote" for the newly-conceived, "neonate"
for newborn baby, "adolescent" for growing-up teenager, "geriatric" for
a pensioner. These terms simply identify different stages in the human
lifespan which begins at fertilisation.
Development
By the end of the twelfth week the baby measures almost 90mm and
weighs 45g. The baby's face, at first broad, now becomes narrower; the
eyes are closed for protection from about 10 weeks until the sixth
month. Boyhood or girlhood is now obvious.
Sensitivity
Two British consultants, one caring for pregnant women and the
other for children after birth, describe human development at this
stage:
"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
Feeling pain
The brain and nerve fibres must be functioning for anyone to feel pain
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
Practising for life outside the womb
"At 11 weeks after conception the foetus starts to swallow the
surrounding amniotic fluid and to pass it back in his urine. He can
also produce complex facial expressions and even smile."
12 Swallowing
prepares the baby for taking in milk at birth. Thumb-sucking has also
been recorded in the foetus.
13
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.
Enlargement of baby and uterus
By sixteen weeks the baby measures 140mm from crown to rump, just
over one third of the size he or she will be at full term, and weighs
around 200g. The heart now pumps 30 litres of blood a day. The uterus
expands and changes shape to accommodate the growing baby; pregnancy
begins to show externally. The doctor can tell approximately how
advanced the pregnancy is by locating the fundus (the top part of the
uterus between the Fallopian tubes, which stretches upwards towards the
mother's chest as the uterus expands).
Hearing
There is evidence that from four months the foetus responds to
sound. Doctors testing unborn children for deafness, while monitoring
their reactions to noise with ultrasound (a technique for visualising
the children in utero), have observed eye movements and "blink-startle"
responses in foetuses of 16 to 32 weeks gestation.
15
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
Sensitivity to light
From the sixteenth week the foetus responds to light. If a
blinking light is shone on to the mother's abdomen, the foetal
heartbeat fluctuates.
22 "In late pregnancy, some light
penetrates through the uterine wall and amniotic fluid, and foetal
activity has been shown to increase in response to bright light."
23 The
womb is a more stimulating environment than some people think; its
occupant is alert and responsive.
After 20 weeks the baby is 190mm from crown to rump and weighs 460g.
Head hair, eyebrows. eyelashes and nails are growing. To protect the
baby's skin from prolonged contact with the amniotic fluid, a greasy
substance called vernix covers the body. Between this stage and birth
the baby will gain weight and will develop an insulating layer of fat
beneath the skin. He or she will also receive maternal antibodies
against some infections as a temporary protection until the infant's
own immune system is better developed.
Waking and sleeping
Foetal activity is affected when the mother is tired or under stress.
24
The baby is usually most notably active when the mother is lying down
at night. The mother feels the baby's kicking and may notice sharp
movements when the baby gets hiccups after drinking the amniotic fluid
or practises its breathing movements. In later pregnancy the foetus has
been observed to show "behavioural states" - waking, calm sleeping, and
"rapid eye movement sleep" which is associated with dreaming in adults.
25
The quest for comfort
The baby still has some room to manoeuvre inside the womb and seeks the position which feels most comfortable:
"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
Survival outside the womb
If the baby is born too early, there is still a good chance that
he or she will survive, given special medical care. A document from the
Royal College of Obstetricians and Gynaecologists (the professional
body of doctors who treat pregnant women) states: "In 1984, 72 per cent
of liveborn infants of 22 to 27 weeks' gestation born at the Bristol
Maternity Hospital survived, as did 64 per cent of infants of 500 to
999 grammes birthweight."
27
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)
Labour and delivery
In the last weeks of pregnancy the baby lies head downwards, as
the head is normally the first part to emerge at birth. Occasionally,
if a baby's position of personal comfort is not changed to fit in with
the normal birth process, there may be a "breech" presentation - rear
end first - which needs medical attention.
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 same before and after birth
After delivery babies who have been studied in utero show the same
individual behaviour that was observed while they were in the womb:
"After birth you see many babies sleeping in the odd positions that
they chose to rest in within the uterus prior to birth ... The good
drinkers in utero are the good drinkers in the nursery and the dainty,
tedious swallowers in utero are the tedious ones out of the uterus as
well ... The behaviour traits also bridge the birth."
28 From the
one-celled zygote to the multi-million-celled infant and adult, every
human being is a distinct individual.
Ante-natal care
A doctor caring for a pregnant woman has two patients, the mother
and the baby. As soon as he is aware of the pregnancy, the doctor will
take the needs of both into account.
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.
Post-natal care
Mother and baby will be visited by the midwife for some days after
the birth to check that all is well with both of them. The mother
should return to her doctor six weeks later for her post-natal
examination to be sure that the uterus has regained its former shape
and that she is otherwise in good health.
| 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. |
| fertilisation | 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. |
- J.M. Beazley, "Assessment of life in utero", Nursing Times, 8 May 1980.
- Jérôme Lejeune, quoted in Professor Jérôme Lejeune and Professor Sir Albert William Liley, The Tiniest Humans, editor Robert Sassone, 1977. Library of Congress No. 77-7681 1, p.69. The Tiniest Humans
is composed from transcripts of testimonies given by Professors Lejeune
and Liley to the Sub-Committee on Constitutional Amendments of the
Committee on the Judiciary, US Senate, 93rd Congress, 2nd Session. 7
May 1974. and the Royal Commission on Contraception, Sterilisation and
Abortion, New Zealand, 1977.
- Sir William Liley, quoted in The Tiniest Humans, as above, p. 16.
- Sir William Liley, quoted in The Tiniest Humans, as above. p.16.
- H. Hamlin, Life or Death by EEG, Journal of the American Medical Association, 12 October 1964.
- T. Humphrey, "Some correlations between the appearance of human fetal reflexes and the development of the nervous system", Progress on Brain Research (1964). 4. 93-135.
- "Earliest feelings help to develop the senses", New Scientist, 7 May 1987. reviewing the research of Maria Fitzgerald published in Nature. 9 April 1987. vol. 326, p. 603.
- H.B. Valman and J.F. Pearson. "What the foetus feels", British Medical Journal, 26 January 1980.
- I.D. Hogg, "Sensory nerves and associated structures in the
skin of human foetuses of 8 to 14 weeks of menstrual age correlated
with functional capability". Journal of Comparative Neurology (1941), 75. 371-410.
- Peter McCullagh, The Fetus as Transplant Donor--Scientific, Social and Ethical Perspectives, John Wiley & Sons 1987. p. 132.
- ibid.
- H.B. Valman and J.F. Pearson, op.cit.
- Sir William Liley. quoted in The Tiniest Humans, as above, p.31.
- J.M. Beazley. op.cit.
- J.C. Birnholz et al. "The development of human fetal hearing", Science (1983), 222. 516-518.
- M. Furuhjelm et al. A Child is Born, Delacorte Press/Seymour Lawrence 1977. p. 116.
- H.B. Valman and J.F. Pearson, op.cit.
- Thomas Verny with John Kelly, The Secret Life of the Unborn Child, Sphere Books. 1987. pp. 7-8. 26.
- A.J. DeCasper & W.P. Fifer, "Of Human Bonding: Newborns Prefer their Mothers' Voices". Science, 208. 1174-1176.1980.
- A.J. DeCasper & M.J. Spence, "Prenatal maternal speech influences newborns' perception of speech sound", Infant Behaviour and Development, 9, 133-150, 1986.
- P.G. Hepper,, "Fetal 'Soap' Addiction", The Lancet, p.1347. 11 June 1988.
- Sir William Liley, "The Fetus as a Personality", The Australian and New Zealand Journal of Psychiatry (1972), 6, 99-105.
- H.B. Valman and J.F. Pearson, op.cit.
- ibid.
- J.O. Drife, "Can the foetus listen and learn?", British Journal of Obstetrics and Gynaecology (1985), 92, 777-779.
- Sir William Liley, quoted in The Tiniest Humans, as above, p.23.
- Royal College of Obstetricians and Gynaecologists, Preterm Labour and its Consequences, 1985, p. 295.
- Sir William Liley, quoted in The Tiniest Humans, as above.
- F. Manning, "Meeting of Royal College of Physicians and Surgeons", Family Practice News, 15 March 1976.
- J.W. Hanson et al. "The effects of moderate alcohol consumption during pregnancy on fetal growth and morphogenesis". Pediatrics (1978), 92, 3, 4574W.
- Professor Hubert Campbell, Emeritus Professor of Medical Statistics, University of Wales
- Professor Sir John Dewhurst, former President of the Royal College of Obstetricians and Gynaecologists
- Professor Peter Gray, Emeritus Professor of Child Health, College of Medicine, University of Wales
- Dr Michael Jarmulowicz, Lecturer in Histopathology, Royal Free Hospital School of Medicine
- Miss Mary Langdon-Stokes, Honorary Consultant Obstetrician and Gynaecologist
- Dr Elliott Larson, Scientific Staff, Clinical Research Centre, Consultant Physician, Northwick Park Hospital
- Professor John Marshall, Emeritus Professor of Clinical Neurology University of London
- Dr John McLean, Senior Lecturer in Embryology and Anatomy, University of Manchester
- Professor David Morrell, Professor of General Practice, Guy's Hospital & St Thomas' Hospital
- Professor David Short, Emeritus Professor of Clinical Medicine, University of Aberdeen
- Professor Ronald Taylor, Department of Obstetrics and Gynaecology St Thomas' Hospital
- Dr Margaret White, General Practitioner
See also
Specialisation of cells (22kB PDF file)