The Pregnant Body Book

258 Pages·2011·47.41 MB·English

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THE
PREGNANT
BODY
BOOK

THE
PREGNANT
BODY
BOOK
DR. SARAH BREWER
SHAONI BHATTACHARYA
DR. JUSTINE DAVIES
DR. SHEENA MEREDITH
DR. PENNY PRESTON
Editorial consultant DR. PAUL MORAN
GENETICS 46
THE MOLECULES OF LIFE 48
HOW DNA WORKS 50
PATTERNS OF INHERITANCE 52
GENETIC PROBLEMS AND 54
INVESTIGATIONS
THE SCIENCE OF SEX 56
THE EVOLUTION OF SEX 58
ATTRACTIVENESS 62
S HUMAN PREGNANCY 6
DESIRE AND AROUSAL 64
THE EVOLUTION OF PREGNANCY 8
THE ACT OF SEX 66
T
MEDICAL ADVANCES 10
BIRTH CONTROL 68
IMAGING TECHNIQUES 12
N GOING INSIDE 14
CONCEPTION TO BIRTH 70
TRIMESTER 1 72
ANATOMY 24
E MONTH 1 74
BODY SYSTEMS 26
WEEKS 1–4 74
THE MALE REPRODUCTIVE SYSTEM 28
T MOTHER AND EMBRYO 76
THE PROSTATE GLAND, PENIS, 30
AND TESTES KEY DEVELOPMENTS: MOTHER 78

N MALE PUBERTY 31 CONCEPTION 80
HOW SPERM IS MADE 32 FERTILIZATION TO IMPLANTATION 84
THE FEMALE REPRODUCTIVE SYSTEM 34 EMBRYONIC DEVELOPMENT 86
O
THE OVARIES AND FALLOPIAN TUBES 36 SAFETY IN PREGNANCY 88
THE UTERUS, CERVIX, AND VAGINA 40 DIET AND EXERCISE 90
THE BREASTS 42 MONTH 2 92
C
FEMALE PUBERTY 43 WEEKS 5–8 92
THE FEMALE REPRODUCTIVE CYCLE 44 MOTHER AND EMBRYO 94
london, new york, melbourne, DESIGNERS Riccie Janus, ILLUSTRATORS
munich, and dehli Clare Joyce, Duncan Turner
DESIGN ASSISTANT Fiona Macdonald

SENIOR EDITOR Peter Frances
INDEXER Hilary Bird CREATIVE DIRECTOR Rajeev Doshi
SENIOR ART EDITOR Maxine Pedliham SENIOR 3D ARTISTS Rajeev Doshi, Arran Lewis
PICTURE RESEARCHERS Myriam Mégharbi,
3D ARTIST Gavin Whelan
PROJECT EDITORS Joanna Edwards, Nathan Joyce, Karen VanRoss
Lara Maiklem, Nikki Sims ADDITIONAL ILLUSTRATORS
PRODUCTION CONTROLLER Erika Pepe
Peter Bull Art Studio, Antbits Ltd
EDITORS Salima Hirani, Janine McCaffrey, PRODUCTION EDITOR Tony Phipps
Miezan van Zyl DVD minimum system requirements
MANAGING EDITOR Sarah Larter
PC: Windows XP with service pack 2,
US EDITOR Jill Hamilton MANAGING ART EDITOR Michelle Baxter Windows Vista, or Windows 7: Intel
or AMD processor; soundcard; 24-bit color display;
US CONSULTANT Dr. Susan L. Sterlacci ASSOCIATE PUBLISHER Liz Wheeler screen resolution 1,024 x 768
RESEARCHER Dr. Rebecca Say ART DIRECTOR Phil Ormerod Macintosh: Mac OS X v10.4; G4, G5,
or Intel processor; soundcard; 24-bit color display;
PROJECT ART EDITOR Alison Gardner PUBLISHER Jonathan Metcalf screen resolution 1,024 x 768
KEY DEVELOPMENTS: MOTHER 96 TRIMESTER 3 154 POSTNATAL 204
DEVELOPMENT
KEY DEVELOPMENTS: EMBRYO 98 MONTH 7 156
MONTH 3 106 WEEKS 27–30 156 RECOVERY AND FEEDING 206
WEEKS 9–12 106 MOTHER AND FETUS 158 THE NEWBORN BABY 208
MOTHER AND FETUS 108 KEY DEVELOPMENTS: MOTHER 160 EARLY RESPONSES AND PROGRESS 210
KEY DEVELOPMENTS: MOTHER 110 KEY DEVELOPMENTS: FETUS 161 THE FIRST TWO YEARS 212
KEY DEVELOPMENTS: FETUS 114 MONTH 8 164
DISORDERS 214
THE SKELETON 118 WEEKS 31–35 166
MOTHER AND FETUS 166 FERTILITY DISORDERS 216
TRIMESTER 2 124 KEY DEVELOPMENTS: MOTHER 168 FEMALE REPRODUCTIVE DISORDERS 218
MONTH 4 126 KEY DEVELOPMENTS: FETUS 169 MALE REPRODUCTIVE DISORDERS 222
SEXUALLY TRANSMITTED 224
WEEKS 13–16 126 MONTH 9 170
DISEASES
MOTHER AND FETUS 128 WEEKS 36–40 170
COMPLICATIONS IN PREGNANCY 226
KEY DEVELOPMENTS: MOTHER 130 MOTHER AND FETUS 172
LABOR AND DELIVERY PROBLEMS 232
KEY DEVELOPMENTS: FETUS 131 KEY DEVELOPMENTS: MOTHER 174
PROBLEMS IN NEWBORNS 234
MONTH 5 134 THE FORMATION OF THE BRAIN 176
PROBLEMS AFFECTING THE 240
WEEKS 17–21 134 KEY DEVELOPMENTS: FETUS 180
MOTHER AFTER DELIVERY
MOTHER AND FETUS 136 THE MOTHER’S CHANGING BODY 182
KEY DEVELOPMENTS: MOTHER 138 THE FETUS’S CHANGING BODY 184
GLOSSARY 244
KEY DEVELOPMENTS: FETUS 139
INDEX 250
LABOR 186
MONTH 6 144
ACKNOWLEDGMENTS 256
WEEKS 18–26 144 PREPARING FOR BIRTH 188
MOTHER AND FETUS 146 THE FIRST STAGE OF LABOR 190
KEY DEVELOPMENTS: MOTHER 148 THE BIRTH 192
KEY DEVELOPMENTS: FETUS 149 ALTERNATIVE BIRTHS 198
THE FORMATION OF THE 152 AFTER THE BIRTH 200
RESPIRATORY SYSTEM ASSISTED BIRTH 202
STATISTICAL SYMBOLS
CROWN–RUMP
HEART RATE LENGTH
CROWN–HEEL
The Pregnant Body Book provides information on a wide range of Published in Great Britain by Dorling Kindersley Ltd. BLOOD PRESSURE LENGTH
medical topics, and every effort has been made to ensure that the
information in this book is accurate. The book is not a substitute
for medical advice, however, and you are advised always to consult A catalog record for this book is available BLOOD VOLUME WEIGHT
from the Library of Congress
a physician or other health professional on personal health matters.

ISBN 978-0-7566-7559-2 BODY SYSTEM SYMBOLS
First American Edition, June 2011–179659
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the above publisher of this book. Discover more at www.dk.com RESPIRATORY SYSTEM
Just one of the millions of human sperm released By seven weeks, most of the structures, organs, and By 14 weeks, the fetus’s facial features can be seen,
will penetrate one egg to create a new life. limbs have already developed in the human fetus. although its head is disproportionately large.
HUMAN PREGNANCY
The growth of a new life inside a woman’s uterus for the nine months of pregnancy is a truly
amazing feat of biology. The creation of life is incredibly complex, and although each pregnancy
is unique, some 130 million women worldwide experience its joys and risks each year.
The human body is capable of many astonishing things. But one of increases by 20 percent by the third trimester—an extra 15 beats
its most intricate, complex, and profound achievements is the ability per minute. Even parts of her immune system will be suppressed
to conceive, carry for nine months, and give birth to our helpless yet so her body does not reject the fetus as “foreign.”
incredibly formed babies. As well as holding the promise of new life,
Making babies
pregnancy involves so many radical changes that it is little wonder
that we marvel at and cherish the birth of children. Despite modern There is more than one way to have a baby. And all living organisms,
concerns about fertility, humans are remarkably fecund. By 2050 we including humans, have evolved to follow one of two strategies. One
will have reached a global population of 11 billion if we continue way to is to reproduce in great numbers, and have lots of offspring
having children at the present rate. at the same time—this is called “big bang” reproduction. Having lots
A pregnant woman’s body adapts in many amazing ways to of babies is extremely energy consuming, and organisms that follow
accommodate and nurture the new life growing inside her. Her this strategy may breed just once and then die, such as Pacific
ligaments relax and stretch to allow space for her womb to grow, salmon, some butterflies, and some spiders. Many of their offspring
and her pelvic joints soften for birth. Her uterus expands from the may perish, but because of their huge numbers, others will survive.
size of a small pear to that of a watermelon by the end of pregnancy. The second, less spectacular strategy, is to have only a few babies
She produces about 50 percent more blood so there is enough to over a lifetime, but to invest more in each one so each individual is
pump around to the uterus and supply the growing fetus with a more likely to survive. This is the strategy that humans follow. It
continuous supply of oxygen and nutrients, and her heart rate allows us to bear high-quality babies that thrive with parental care.
A male Emperor penguin incubates his egg and The marginated tortoise produces up to three A newborn Lemon shark emerges from its mother
fasts while caring for his unborn offspring. clutches of between four and seven eggs a year. while remora fish break and eat the umbilical cord.
At 20 weeks, the baby is now growing rapidly. Eyebrows, By 29 weeks, the baby’s face is starting to fill out A healthy baby girl cries moments after being born. Her
eyelashes, and hair will have grown by this stage. with fat as its rapid growth and weight gain continue. skin is covered in vernix, which protects against infection.
How other animals reproduce
the young are ready to hatch, the animal will “give birth” to a clutch
As humans we may take pregnancy for granted, but there are many of eggs, which will immediately spawn. Some fish and reptiles, such
weird and wonderful ways in which to produce the next generation. as sharks and anacondas, employ this strategy of ovivipary.
Some animals simply lay eggs, others carry eggs inside their bodies
Parental duties
until they are ready to hatch, and many, like humans, go through
pregnancy and bear live young. Although we might think that only As soon as an embryo is conceived, the division of labor between
birds and lower orders of animals lay eggs, there are even a few mother and father begins. In many species the mother bears the
quirky mammals, such as the Duck-billed Platypus, that do so. burden of laying and guarding eggs, or pregnancy and birth, and
Animals that lay eggs follow ovipary; oviparous animals include even raising the offspring. But males can have a crucial role. In some
all birds, most reptiles, and most fish. The egg comprises yolk, which species, the male becomes “pregnant.” Male seahorses and pipefish
contains all the embryo’s nourishment, and its protective shell and nurture fertilized eggs in brood pouches. The female deposits her
layers keep the embryo safe inside. Often a parent has to keep eggs eggs in the male’s pouch, where they are fertilized by sperm. And the
warm and protect them; many species incubate eggs until they hatch. male later “gives birth.” Male Emperor penguins also make devoted
At the other end of the reproductive spectrum are those animals fathers, painstakingly incubating a single egg on their feet for nine
that house, protect, warm, and nourish developing embryos inside weeks in freezing temperatures, allowing their mates to go and feed
their own bodies. Humans, most other mammals, and a few rare after egg-laying. They, like many bird species, raise offspring together.
reptiles, fish, amphibians, and scorpions, do this. This is known as Human children also thrive with both mother’s and father’s care, or
vivipary. Humans and many other mammals are able to nurture other family support networks, because humans need a long, intense
young inside the uterus thanks to a special organ that develops period of parenting.
during pregnancy: the placenta. Not all viviparous animals have Some animals, such as kangaroos, can stop their pregnancies by
this, and the placenta may have been pivotal in human evolution. stalling the embryo from implanting in the womb. The pregnancy
But there are some animals that fall between egg-layers and can then be started weeks, or even a year, later. These animals have
live-bearing animals—those whose embryos develop in eggs that evolved a way of bearing offspring when they can survive. Evolution
remain within the animal’s body, somewhat like a pregnancy. When has honed pregnancy to give offspring the best chances possible.
The common Japanese male seahorse becomes Common Brushtail Possums, unlike most mammals, are not This four-day-old Japanese macaque reaches for its
pregnant. The tiny seahorses are independent once born. nourished by a placenta but entirely on their mother’s milk. mother’s nipple, and it may nurse for up to 18 months.
This color-enhanced MRI scan reveals the size This colored electron micrograph shows fetal tissues
and some of the anatomical features of the brain (villi) that protrude into the placenta, allowing for the
(shown in green) of a 36-week-old fetus. exchange of vital gasses, nutrients, and wastes.
THE EVOLUTION OF PREGNANCY
Pregnancy evolved in humans to allow for extended care of the growing fetus and enable
us to have large-brained babies with astonishing learning capabilities. The female body
has evolved to cope with and adapt to the challenges of carrying a fetus for nine months.
Pregnancy may be an amazing condition, but it is not without perils. period of care and level of nourishment; and the longer this period
Why would humans evolve such a complex and risky way of lasts, the stronger the offspring are. Although a placenta is not
reproducing when there are simpler methods available? The answer, essential for pregnancy (marsupials have a much simpler equivalent
quite simply, is that pregnancy’s benefits outweigh the negatives. organ), it helps considerably in giving human babies a head start.
Carrying a fetus in the uterus for nine months ensures each aspect Crucially, a long pregnancy allows humans to bear large-brained
of its environment is controlled: it is kept warm, safe, nourished, and babies. Large, complex brains, plus the ability to walk upright, makes
supplied with oxygen. If we had evolved to lay eggs instead, as a humans special. Human brain volume is a massive 67–104 cubic
handful of mammals do, the fetus would be limited to the supply of inches (1,100–1,700 cubic cm) compared with the 18–31 cubic inches
nutrients contained in the yolk. Pregnancy allows us to extend the (300-500 cubic cm) of our closest living relative, the chimpanzee.
PREGNANCY FACTFILE
Pregnancy, birth, and newborns vary incredibly within the animal world. Human do not have a complex placenta, but then make up the difference with extended
newborns are vulnerable compared with those of other mammals—wildebeest maternal care. Human babies require much parental care. In terms of motor,
calves can run from predators within hours of birth, while bat babies can fly chemical, and brain development, a human baby displays the same levels at
within two to four weeks of birth. Marsupials have short pregnancies because they about nine months as those displayed by its primate cousins at birth.
HUMAN BLUE WILDEBEEST ELEPHANT RED KANGAROO MOUSE BAT
Gestation period 40 weeks 8 months 22 months 32–34 days 18–21 days 40 days to 8 months
Litter size 1 or 2 (very rarely more) 1 1 (rarely twins) 1 8–12 1 or 2 (3 or 4 in
some species)
Average weight 6–9 lb (2.7–4.1 kg) 49 lb (22 kg) 198–265 lb (90–120 kg) 1⁄33 oz (0.75 g) 1⁄50–1⁄19 oz (0.5–1.5 g) 0–30 percent of
mother’s body weight
Ability at birth Helpless: cannot hold up Can stand within Long period of Climbs into mother’s Helpless; no pigment Completely dependent
own head; can focus eyes 15 minutes; can eat grass maternal care and pouch unaided within or hair; closed eyes and on mother for food and
to see only 171⁄2 in (45 cm) within 10 days; weaned learning; weaned 3 minutes; leaves the ears. By 3 weeks, have protection, but mature
ahead. Very long period of at nine months at 4–5 years pouch at 240 days but adult hair, open eyes, quickly and fly within
parental care required to suckles for another ears, and teeth and 2–4 weeks; weaned
reach adulthood 3–4 months can be weaned shortly after
Time until next Can be within months, 1 year 4–6 years, Can get pregnant 1 day Can conceive within Generally breed once
pregnancy although many depending on after birth but the hours of birth, but can a year but has various
increase spacing female’s age pregnancy is paused delay pregnancy by up strategies to delay
until a suckling joey to 10 days if still nursing pregnancy
is 200 days old by halting implantation
8