pregnancy

World of the Body: pregnancy

The biological event of pregnancy is established when a fertilized egg successfully implants itself in the lining of the uterus, about a week after conception.

The corpus luteum, which formed in the ovary when it released the egg, secretes hormones that keep the uterine lining in a suitable state for implantation; if fertilization had not occurred, this hormone secretion would have ceased, and the uterine lining would be shed after two weeks. The hormonal ‘message’ from an implanted embryo via the mother's bloodstream to the ovary prevents its own rejection.

Early pregnancy continues to be maintained by the hormones produced by the corpus luteum in the ovary that produced the egg; but later, when the placenta has fully developed (by about 3 months), this takes over the maintenance function through its own hormone production.

Pregnancy produces profound changes in the mother, which may be detected from early stages. There is a marked rise in the output of the heart by 3 months, and it rises further as pregnancy advances, reaching 30-40% above the non-pregnant level by the end. This rise is mainly due to an increase in output with each contraction of the heart muscle (stroke volume), although the heart rate also increases. The volume of blood in the circulation also increases, with a greater increase in plasma volume than in red blood cells, producing the so-called ‘physiological anaemia of pregnancy’. Although these changes in the circulation can produce serious consequences for pregnant women with certain types of heart disease, they are necessary to deal with the demands of the growing fetus, placenta, and uterus, and have no deleterious effects in healthy mothers.

There are changes in the breasts from an early stage of pregnancy; they enlarge, and surface blood vessels become prominent, reflecting preparation for eventual lactation. Hormonal changes cause development of the glandular tissue: the potential milk-secreting cells and the ducts to the nipples. Although the hormones which cause milk production (prolactins) are produced during pregnancy, the actual secretion of milk is suppressed by other hormones until after delivery.

Other changes include a laxity of the joints, which ultimately may assist labour and birth, and increased brown pigmentation of the skin (‘chloasma’ if in the face). Stretch marks are other hallmarks of pregnancy in the skin. The mother has increased blood flow to the kidneys, and therefore increased urine production, and this results in more frequent visits to the toilet — a common symptom of early pregnancy. The placenta produces large amounts of the hormone progesterone, which appropriately prevents the uterine smooth muscle from contracting, but also relaxes smooth muscle throughout the body. This results in many of the so-called minor symptoms of pregnancy, including constipation and heartburn, and it may exacerbate varicose veins.

The mother's appetite usually increases — but the extra energy requirement for the whole pregnancy is not more than about 60 000 Kcal — or 20-24 extra days' worth of food intake. Where there is abundance of food, excessive eating and undue weight gain are not uncommon, although there is in fact a normal physiological tendency to lay down more fat stores in the earlier months. Appetite for particular foods and drinks, or rejection of others, can be capricious. Occasionally the nausea of morning sickness, which is common in early pregnancy, may extend to other times of day, may be more severe than usual, and may be accompanied by vomiting or may be prolonged into later pregnancy.

The uterus enlarges considerably to accommodate the growing fetus. It emerges from the pelvis at around 12 weeks, reaches the navel at around 22 weeks, and the ribs at around 36 weeks.

Pregnancy normally reaches its dramatic conclusion with the onset of labour, between 35 and 39 weeks after conception.

The establishment of antenatal care to detect problems during pregnancy, and to attempt to ensure that women were in good health at the time of delivery, is generally credited to J. W. Ballantyne, an Edinburgh obstetrician, who took the first step towards this at the beginning of the twentieth century. Clinics became established in major centres in the UK, the US, and Australia by the time of the first World War.

— Jim Neilson

Pregnancy: the cultural context

Pregnancy occupies potent symbolic space in cultures around the world. As both the development of a life and a significant transitional event within the woman's lifespan, pregnancy becomes the focus of cultural desires and anxieties around gender, power, selfhood, and even nationhood. Medical technology has increasingly refigured the physiological possibilities of pregnancy, especially through assisted reproduction for the infertile, its extensions to surrogacy and older-age pregnancy, and through genetic testing.

One of the most common cultural mythologies about pregnancy is that it is evidence of full womanhood. Because mothering is so closely tied into cultural gender roles, to be pregnant is to fulfill one's gendered destiny. Although this emphasis on pregnancy emerges from culturally-specific definitions of femininity and womanhood, many people see the urge as instinctive and the process itself as natural, even as industrialized countries increasingly rely on medical technologies to avoid, create, sustain, and complete pregnancies.

Differential worldwide rates of fertility, infant mortality, and maternal mortality have led the World Health Organization to focus attention on women's differential access to services and opportunities with respect to men as well as between different countries and regions. At least partly because of this focus, all three of these rates dropped by about one-third over the twenty years up to 1998, when overall fertility rate was 2.7 births per woman; Europe was lowest at 1.6, while Africa remained highest at 5.4. Infant mortality rate world-wide was 57 deaths per 1000 live births, whereas highly industrialized countries such as the US and the UK had rates as low as 7 deaths per 1000. Maternal mortality rate (expressed as deaths per 100 000 births) in the UK showed a dramatic drop from the 1930s onwards, whereas until then it had been essentially unchanged at around 500 for 100 years; in the 1980s it was below 10. By the end of the twentieth century, according to the World Health Organization, developed nations averaged a rate of 27 deaths per 100 000 live births. This contrasts with 480 on average in developing nations (comparable to Victorian Britain), with some regions as high as 1000. The global average was 430. While these numbers are specific to pregnancy, and associated with disparities in medical services and supplies, they may also reflect the status of girls and women in different cultures, and their relative power in their societies.

Pregnancy, in the natural order of things, becomes possible and physiologically appropriate as soon as ovulation is established after the menarche, usually during the teens, or even earlier. But in modern developed societies, the issue of teenage pregnancy is increasingly a concern to both moral leaders and health educators. In the UK the rate has been rising: in 1997, under-16s accounted for over 8% of all known conceptions in the under-20 age group; meanwhile rates declined in other European countries and in the US there has been some reduction since the late 1980s. The spectre of the pregnant young girl is often cited as a wake-up call for issues as diverse as promiscuity, health education, and the viability of the welfare state.

Young women who maintain pregnancies are less likely to finish or continue their education, face greater marital instability, have fewer lifelong assets, and have lower incomes later in life than women who did not become pregnant young. Yet pregnant teenagers have become symbolic more of the decline of social morality than of the lack of resources granted to young women worldwide.

Teenage and unmarried pregnancies have always existed, but the advent of new methods of contraception in the twentieth century has changed the significance and experience of pregnancy for hundreds of millions of women worldwide. Before these methods were widely and legally available, pregnancy often signified the end of a woman's career choices, if not her need to work; closely successive pregnancies, when timing could not be controlled, often led to early death, as it still does in many places worldwide today.

Female-directed methods, such as the modern intrauterine device (IUD) and hormonal control by the Pill or by long-lasting implants, have allowed women to choose not only the occurrence but also the timing of pregnancy. Earlier barrier methods of contraception had allowed women to control their pregnancies somewhat, although they also required them to negotiate with their husbands. Hormonal contraceptives have changed many women's relationship to pregnancy by putting the choice in their own hands. Indeed, world health leaders are calling for this globally as a step towards women's liberation from socially imposed controls.

Relative size of the uterus at the end of (a) the third; (b) the sixth; and (c) the ninth month. Near the end of pregnancy the head usually sinks down into the pelvis (d) ; this is called 'lightening'. Reproduced, with permission, from Youngson (1995), Encyclopedia of family health, Bloomsbury Publishing
Relative size of the uterus at the end of (a) the third; (b) the sixth; and (c) the ninth month. Near the end of pregnancy the head usually sinks down into the pelvis (d) ; this is called 'lightening'. Reproduced, with permission, from Youngson (1995), Encyclopedia of family health, Bloomsbury Publishing



As women have been afforded more control over pregnancy, they have also been granted more responsibility for the outcomes. European societies of the seventeenth and eighteenth centuries often assumed that strong maternal emotions would mark the fetus; disfigured babies were blamed on maternal viewing of disfigured persons or other disturbing events. Modern versions of maternal responsibility relate to the links between birth outcomes and maternal behaviors, such as drinking alcohol, smoking cigarettes, or taking drugs (licit or illicit). Whilst high risks for fetal abnormality are established for some maternal excesses (e.g. alcohol, cocaine), for specific nutritional deficiencies (some vitamins and trace elements), and for certain prescription drugs, prohibitions and exhortations may often be overstated. While women around the world and through time have made sacrifices and personal changes for the good of the fetus, this modern focus on risk and risk management has defined what constitutes ‘the good of the fetus’. The rights of women to bodily integrity and self-determination seem sometimes to be undermined by a society's concern to protect the fetus from any possibility of harm.

In the latter half of the twentieth century also, medical technologies began to address infertility, and to develop methods of assisted reproduction. These have not only benefited childless couples, but have also resulted in extensions of pregnancy in two other contexts. Surrogacy, the creation and carrying of a pregnancy for another woman or couple, has gained both prominence and notoriety in recent years. The practice has spawned high-profile custody cases, the most famous of which is the Mary Beth Whitehead case, as well as more prosaic cases of women carrying babies for their sisters, daughters, and friends — as demonstrated in Sisters, US television drama. While this has created legal disputes about the relative importance of genetic parenthood over physical parenthood, it has also enabled infertile couples, including lesbian couples, to create genetically-connected families.

The medical procedures involved in surrogacy — hormone treatments, ova extraction, in-vitro fertilization (IVF), and gamete intrafallopian tube transfer (GIFT), for example — have also allowed post-menopausal women to bear children. A number of cases have recently occurred in the US, where several women in their 50s and 60s have given birth. These events touched off a national debate about appropriate motherhood and the dual pressures towards a career and a family that modern women often face.

Even routine pregnancies in industrialized countries are increasingly technological, as couples are offered genetic counselling, and ultrasound scans and amniocentesis have become commonplace. While these procedures can sometimes highlight problems that medical technology can successfully address, they may create anxiety through false positives, nebulous results, and the construction of pregnancy as problematic, instead of generally successful. While technology has long been able to transform, and has often usefully assisted the procedure of birth, these diagnostic procedures have only recently allowed the medical profession immediate and even cellular control over the management of pregnancy.

Pregnancy is essentially a personal event, but international attention is currently focusing on pregnancy around the world. While the World Health Organization is focused on lowering rates of fertility, infant mortality, and maternal mortality in order to improve the lives of women and children, national concern for differential pregnancy rates frequently betrays racist undertones; industrialized countries, and well-off populations within them, worry about how ‘they’ will outnumber and overtake ‘us’. Although often categorized as a ‘woman's issue’, pregnancy and the social attitudes towards it thus highlight important cultural issues, such as the relationship between life and technology, the definitions of gender roles in a given society, and the relationship between nations and their citizens.

— Julie Veddoer