Medical management of normal pregnancy

Medical management of normal pregnancy

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Essentials

Reducing the number of maternal deaths is one of the United Nation’s eight Millennium Development Goals, yet despite this initiative maternal deaths are increasing in some parts of Africa, usually from readily preventable causes that would not occur in the presence of a skilled birth attendant.

Diagnosis of pregnancy—this can be achieved within a day of missing a menstrual bleed by identifying a rise in concentration of urinary human chorionic gonadotropin.

Antenatal checks—at the first antenatal visit a medical and obstetric history is combined with:

  • cardiovascular examination;
  • urinalysis—proteinuria, bacteriuria; and
  • laboratory tests—HIV, hepatitis B, and syphilis; screening for sickle cell disease, thalassaemias, and rhesus antibodies.

Further antenatal checks (obstetric, blood pressure, urinalysis) are usually performed around 16, 25, 28, 31, 34, 36, 38 and 40 weeks, then weekly until delivery.

Clinical features of pregnancy—aside from those obviously related to a growing fetus in the abdomen, symptoms of a healthy pregnancy include fatigue, palpitations, dizziness, syncope, dyspnoea, nausea, vomiting, headaches, and oedema, and signs include full and bounding arterial pulses and an ejection systolic flow murmur.

General management—pregnant women may require nutritional advice (see: Nutrition in pregnancy) and should be advised to take regular exercise, stop smoking, and avoid heavy alcohol consumption (but there is no evidence that 1 to 2 units of alcohol once or twice a week is harmful to the fetus).

Clinical priorities—when managing medical disorders in pregnancy, the clinician’s priority is to treat the maternal condition, sometimes at the risk of fetal well-being.

Introduction

Until recently Homo sapiens thrived with nothing but the most primitive antenatal care, and the first introductions of hospital-based childbirth in the United Kingdom and elsewhere were disasters. In the mid 19th century it became clear to some that unhygienic medical practice was responsible for puerperal sepsis and a high maternal mortality rate, but not until the 1930s did the maternal mortality rate in the United Kingdom fall from more than 1 in 100 deliveries in the worst maternity hospitals to less than 1 in 7000 deliveries today. Lessons learnt over the last century in the developed world are still not being implemented around the world, and globally there are over 500 000 pregnancy-related maternal deaths each year, mostly in sub-Saharan Africa and Asia.

Reducing the number of maternal deaths is one of the United Nations Millennium Development Goals, yet despite this initiative maternal deaths are increasing in some parts of Africa. Women in Sierra Leone have a 1:6 chance of death during their reproductive lifetime. The tragedy is that these are usually deaths from readily preventable causes that would not occur in the presence of a skilled birth attendant. Added problems such as HIV/AIDS and health systems disrupted by war exacerbate the problem. Furthermore, for every maternal death there are at least 20 additional women who suffer serious pregnancy-related conditions that cause lifelong disabilities.

In the developed world, the dramatic reduction in the number of maternal deaths from obstetric complications has not been matched by a similar fall in deaths associated with pre-existing maternal disease. This is partly due to the success of modern medicine in helping more women with congenital or chronic disease to survive until reproductive age, and partly due to the inability of physicians to manage otherwise familiar medical conditions during pregnancy.

Misplaced concern about fetal welfare often denies the mother life-saving investigations and treatment, hence substandard care is responsible for many maternal deaths. By contrast, the general physician must be aware of the symptoms and signs of normal pregnancy and familiar with advice on how women should prepare for and maintain a healthy pregnancy, or else clinical anxiety may lead to meddlesome and sometimes harmful intervention when a doctor is presented with a healthy but symptomatic pregnant woman.

Maternal factors that influence pregnancy outcome

Maternal age

There is a trend among women in the developed world to delay childbearing. In Sweden, the mean maternal age at the birth of the first child increased between 1974 and 2001 from 24.4 years to 28.5 years. The number of women delaying pregnancy until after the age of 40 years has also increased, yet women over 35 years have an increased risk of pregnancy-induced hypertension, gestational diabetes, thrombosis, and adverse pregnancy outcome.

The risk of fetal aneuploidy, most notably trisomy 21 (Down’s syndrome), also increases with maternal age: at 25 years of age it is 1:1250, at 35 years 1:385, and at 45 years 1:30. These risks can be refined between 11 weeks 0 days and 13 weeks 6 days of gestation by the ‘combined test’ (nuchal translucency, which is an ultrasound measurement of skin-fold thickness at the back of the fetal neck, combined with a maternal serum measure of β-human chorionic gonadotropin, and pregnancy-associated plasma protein A). For women who book for antenatal care the most clinically and cost-effective serum screening test is the triple or quadruple test that should be offered between 15 and 20 weeks gestation. Women found to be at high risk of a chromosomal abnormality can be offered diagnostic testing with amniocentesis, which carries a 0.5 to 1.0% risk of miscarriage.

Maternal weight

Maternal health is threatened by a high prepregnancy weight, as measured by the body mass index (BMI): pre-eclampsia, gestational diabetes mellitus, and late fetal death are all more common in overweight (BMI 25–30 kg/m2) and obese women (BMI > 30 kg/m2), and it is of concern that nearly half of all women of childbearing age in the developed world are now either overweight or obese. Conversely, underweight women (BMI <19 kg/m2) are more prone to have babies with lower birth weights.

Weight gain during healthy pregnancy varies between 10 and 16 kg in Western societies, i.e. about 20% of prepregnancy weight. Lean, nulliparous, healthy, pregnant women who eat to appetite gain 0.65 kg to 1.1 kg during the first 10 weeks of pregnancy, about 0.45 kg/week during the second trimester, and about 0.36 kg/week during the last trimester. Maternal weight gain correlates poorly with fetal growth. Unless the mother is underweight before pregnancy (BMI <19) or has hyperemesis gravidarum, conditions that often coexist, regular antenatal measurements of maternal weight are not helpful and fetal growth is most accurately assessed by serial ultrasound measurements.

Past medical history

Pregnancy is a medical stress test for the woman, which is particularly evident in those with chronic medical disorders. A diseased maternal organ system may transiently lose residual function in attempting to accommodate the physiological demands of pregnancy. For example, women with classic risk factors for hypertension are more likely to develop pre-eclampsia, and women with subclinical insulin resistance are at increased risk of gestational diabetes. Similarly, women with inherited thrombophilias may develop thrombosis only in combination with the hypercoagulable environment of healthy pregnancy. These gestational syndromes are likely to be associated with an adverse fetal outcome, but the physiological changes of pregnancy are not always damaging: some conditions improve, while others deteriorate (Bullet list 1).

Bullet list 1 Effect of pregnancy on pre-existing conditions

Conditions that tend to improve during pregnancy

  • Mitral and aortic regurgitation
  • Raynaud’s phenomenon
  • Mild hypertension (worsens towards term)
  • Hyperthyroidism (may transiently worsen in first trimester)
  • Sarcoid
  • Rheumatoid arthritis
  • Multiple sclerosis (may relapse postpartum)
  • Peptic ulceration

Conditions that are unpredictable during pregnancy

  • Asthma
  • Systemic lupus erythematosus (may relapse postpartum)

Conditions that tend to deteriorate during pregnancy

Cardiovascular system

  • Mitral and aortic stenosis
  • Pulmonary hypertension (40% risk of maternal mortality)
  • Congenital cyanotic heart disease
  • Supraventricular arrhythmias (in third trimester)
  • Vascular aneurysms 
  • Haemolytic–uraemic syndrome/thrombotic thrombocytopenic purpura
  • Epistaxis
  • Varicose veins and haemorrhoids
  • Venous thrombosis
  • Antiphospholipid syndrome (deep vein thrombosis and recurrent miscarriage)

Respiratory system

  • Viral pneumonia
  • Pulmonary embolus

Gastrointestinal system

  • Gastro-oesophageal reflux (especially in third trimester)
  • Cholestatic liver disease (in third trimester)
  • Inflammatory bowel disease, in some women
  • Constipation

Genitourinary system

  • Upper urinary tract infections (pyelonephritis)
  • Reflux nephropathy
  • Renal impairment (glomerular filtration rate <30 ml/min)

Musculoskeletal system

  • Osteoporosis
  • Osteoarthritis
  • Back pain

Endocrine system

  • Diabetes mellitus
  • Diabetes insipidus
  • Hypothyroidism
  • Hyperlipidaemia
  • Pituitary macroadenoma

Neurological system

  • Epilepsy
  • Cerebrovascular accidents, especially postpartum
  • Depression (postnatal)
  • Headache, in first and second trimester
  • Carpal tunnel syndrome, third trimester

Haematological system

  • Anaemia and thrombocytopenia
  • Sickle cell disease
  • Thrombophilias Infections
  • Intracellular pathogens (e.g. malaria, leprosy, listeria)

Family history

Gestational conditions tend to run in families. Pre-eclampsia, gestational diabetes mellitus, obstetric cholestasis, and probably both hyperemesis gravidarum and postnatal depression have genetic components. Inherited thrombophilias also have a direct impact on pregnancy outcome.

Infertility and multiple pregnancies

In 1978 the first baby was born by in vitro fertilization (IVF), and she herself has now given birth to a healthy child following natural conception. Over the last 30 years well over 1 million babies have been born worldwide using IVF technology. One-quarter of these pregnancies have resulted in multiple births, compared with 11 per 1000 pregnancies following natural conception. In the United Kingdom this has led to a 66% increase in twin births, which itself has increased the frequency of maternal complications in often older mothers. The cause of infertility may also lead to problems in pregnancy, e.g. women with polycystic ovary syndrome are at increased risk of pregnancy-induced hypertension and gestational diabetes.

Ovarian hyperstimulation syndrome

To increase the yield of eggs, women receiving IVF undergo ovarian stimulation with gonadotropins, following which up to 10% develop an ovarian hyperstimulation syndrome that is severe in 1% of cases. This occurs when multiple follicles each develop into a corpus luteum, producing excessive amounts of progesterone and resulting in massive ovarian enlargement and increased vascular permeability. Protein-rich fluid shifts into serous cavities, causing ascites and (in more severe cases) pleural and pericardial effusions. Haemoconcentration and hypotension result, increasing the risk of thrombosis and reducing renal perfusion. Most cases are mild, but death has followed acute respiratory distress, hepatorenal failure, thromboembolism, and rupture of grossly enlarged ovaries. Management is mainly supportive, including careful fluid balance, thromboprophylaxis, analgesia, and adjustment of luteal stimulation under the guidance of a specialist in assisted conception. In some cases paracentesis can be used to transiently relieve abdominal pressure symptoms.

Diagnosis of pregnancy

Pregnancy can be diagnosed within a day of missing a menstrual bleed by identifying a rise in concentration of urinary human chorionic gonadotropin (hCG). At this time the embryo is 2 weeks old, but obstetric convention dictates that the gestation of pregnancy is calculated from the first day of the last menstrual period, i.e. 2 weeks earlier than embryonic age. Teratogenic drugs interfere with organ development in the 2 to 8 weeks postconception (embryonic period). After 9 weeks and until delivery, the conceptus is known as a fetus, but it is still vulnerable to the effects of drugs given to the mother.

Read more:

Screening of maternal health during pregnancy

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