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Antepartum Care: Preconception and Prenatal Care, Genetic Evaluation and Teratology, and Antenatal Fetal Assessment
Clinical Keys for this Chapter
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Preconception counseling is an important component of preventive care for couples that are considering pregnancy. It can identify risks related to family history, maternal medical conditions, and fetal and maternal chromosomal/genetic disorders that may result in congenital abnormalities. A simple screening tool called Before Pregnancy is available electronically at StudentConsult.com to facilitate the process of preconception assessment and counseling.
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Adequate prenatal care, including nutritional counseling, is essential for obtaining the best pregnancy outcomes. Early pregnancy complications, secondary to factors related to the mother, her fetus, or the placenta, occur in some pregnancies. Early recognition and management of these problems is vital for the success of the pregnancy. During follow-up visits, it is important to reassure women that their pregnancy is progressing normally or initiate appropriate testing when necessary.
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Traditionally, women older than 34 years of age have been advised to have prenatal testing because they are at increased age-related risk for having offspring with chromosomal and genetic abnormalities and the risk of the more invasive techniques is less than the risk of finding abnormalities. Recently, microarray comparative genomic hybridization (microarray-CGH) has been introduced into clinical practice. There are many submicroscopic chromosomal abnormalities that can now be detected with microarray-CGH that are not maternal age-related. Current guidelines therefore recommend that prenatal diagnostic testing with amniocentesis or chorionic villus sampling (CVS) be offered to all pregnant women regardless of their age.
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A number of noninvasive tests are available for screening for fetal chromosomal abnormalities. These include second-trimester maternal serum screening (Quad-Screen), which offers a trisomy 21 detection rate of 81%; first-trimester serum screening combined with ultrasonic measurement of nuchal translucency and visualization of nasal bone, which has a Down syndrome detection rate of 93%, and integrated first- and second-trimester screening, which increases the detection rate to 95%. Recently, noninvasive prenatal testing (NIPT) using cell-free fetal DNA from maternal plasma has been introduced. This less invasive type of prenatal testing has been reported to have a detection rate of >99% for trisomy 21 and trisomy 18. False positive rates for these screening tests have been reported and they should not be considered diagnostic. CVS or amniocentesis is required for confirmation (see Chapter 17 ).
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Evaluation of fetal well-being during pregnancy starts with the mother's “kick count.” When <10 fetal movements are detected in 1 hour on two separate occasions, nonstress testing (NST) and ultrasonic assessment should be performed. When the amniotic fluid index (AFI), determined by ultrasonic measurement, is combined with fetal movements, an NST, and evaluation of fetal tone, the assessment is referred to as a biophysical profile. These techniques have largely replaced the contraction stress test for antenatal fetal assessment.
Pregnancy, to many women, is one of the greatest experiences of their lives. Even before conceiving, a woman may contemplate or ask whether her child will be normal at birth and whether pregnancy will be safe for her. Preconception and prenatal counseling by the well-informed health care professional can offer a sense of security to these women and deliver some of the most cost-effective preventive measures in all of health care. The purpose of this chapter is to provide the reader with a basic understanding of the appropriate evaluation and the optimal care that should be provided when a woman is thinking of trying to conceive, or has become pregnant.
Preconception Care
Ideally, “prenatal care” should begin before pregnancy. Organogenesis begins early in pregnancy and placental development starts with implantation, about 7 days after conception. Poor placental development has been linked to preeclampsia, preterm birth, and intrauterine growth restriction (IUGR), all of which are associated with low birth weight (<2500 grams), and may play a role in fetal programming of chronic diseases later in life. This is known as the Barker hypothesis (see Chapter 1 ). In addition, obesity has become a world-wide problem associated with metabolic dysregulation, and must be addressed before pregnancy if outcomes are to be improved.
By the time most pregnant women have their first prenatal visit, it is too late to address the risk of low birth weight and obesity, and to reduce the risk of some birth defects. The growing recognition of the importance of women's health before pregnancy has drawn increasing attention to the need for more effective and timely preconception care. Several models of preconception care have been developed. According to one model, the major components of preconception care include 12 risk assessments and 6 health promotions and these are summarized in Table 7-1 . To cover each of the 18 components would require multiple visits to a health care provider, and this is often not acceptable to young women.
TABLE 7-1
Elements of Preconception Counseling and Care
| Major Components of Preconception Care | Risk Assessment |
|---|---|
| Reproductive life plan | Ask your patient if she plans to have any (more) children, and how long she plans to wait until she (next) becomes pregnant. Help her develop a plan to achieve those goals. |
| Past reproductive history | Review prior adverse pregnancy outcomes, such as fetal loss, birth defects, low birthweight, and preterm birth, and assess ongoing biobehavioral risks that could lead to recurrence in a subsequent pregnancy. |
| Past medical history | Ask about past medical history, such as rheumatic heart disease, thromboembolism, or autoimmune diseases that could affect future pregnancy. Screen for ongoing chronic conditions such as hypertension and diabetes. |
| Medications | Review current medication use. Avoid category X drugs and most category D drugs unless potential maternal benefits outweigh fetal risks (see Box 7-3 ). Review use of over-the-counter medications, herbs and supplements. |
| Infections and immunizations | Screen for periodontal, urogenital, and sexually transmitted infections as indicated. Discuss TORCH (toxoplasmosis, other, rubella, cytomegalovirus, and herpes) infections and update immunization for hepatitis B, rubella, varicella, Tdap (combined tetanus, diphtheria and pertussis), human papillomavirus, and influenza vaccines as needed. |
| Genetic screening and family history | Assess risk of chromosomal or genetic disorders based on family history, ethnic background, and age. Offer cystic fibrosis screening. Discuss management of known genetic disorders (e.g., phenylketonuria, thrombophilia) before and during pregnancy. |
| Nutritional assessment | Assess anthropometric (body mass index), biochemical (e.g., anemia), clinical, and dietary risks. |
| Substance abuse | Ask about smoking, alcohol, drug use. Use T-ACE (tolerance, annoyed, cut down, eye opener) or CAGE (cut-down, annoyed, guilty, eye-opener) questions to screen for alcohol and substance abuse. |
| Toxins and teratogens | Review exposures at home, neighborhood, and work. Review Material Safety Data Sheet and consult local Teratogen Information Service as needed. |
| Psychosocial concerns | Screen for depression, anxiety, intimate-partner violence, and major psychosocial stressors. |
| Physical examination | Focus on periodontal, thyroid, heart, breasts, and pelvic examination. |
| Laboratory tests | Check complete blood count, urinalysis, blood type and antibody screen, rubella, syphilis, hepatitis B, HIV, cervical cytology; screen for gonorrhea, chlamydia, and diabetes in selected populations. Consider thyroid-stimulating hormone. |
| Major Components of Preconception Care | Health Promotion |
| Family planning | Promote family planning based on a woman's reproductive life plan. For women who are not planning on getting pregnant, promote effective contraceptive use and discuss emergency contraception. |
| Healthy weight and nutrition | Promote healthy prepregnancy weight through exercise and nutrition. Discuss macro- and micronutrients including 5-a-day and daily intake of multivitamin containing folic acid (see www.fns.usda.gov/5day ). |
| Health behaviors | Promote such health behaviors as nutrition, exercise, safe sex, effective use of contraception, dental flossing, and use of preventive health services. Discourage risk behaviors such as douching, nonseatbelt use, smoking, alcohol and substance abuse. |
| Stress resilience | Promote healthy nutrition, exercise, sleep, and relaxation techniques; address ongoing stressors such as intimate partner violence; identify resources to help your patient develop problem-solving and conflict resolution skills, positive mental health, and relational resilience. |
| Healthy environments | Discuss household, neighborhood, and occupational exposures to metals, organic solvents, pesticides, endocrine disruptors, and allergens. Give practical tips such as how to reduce exposures during commuting or picking up dry cleaning. |
| Interconception care | Promote breastfeeding, back-to-sleep, positive parenting behaviors, and reduce ongoing biobehavioral risks. |
The major problem associated with the implementation of preconception care is a lack of consensus on the necessary components of the care. For some, preconception care means a single prepregnancy check-up a few months before couples attempt to conceive. A single visit, however, may be inadequate to address some problems such as smoking cessation or attaining and maintaining a healthy weight.
For others, preconception care should become an important part of comprehensive well-woman care, universally implemented from prepubescence to menopause. In practice, however, asking providers to squeeze more into their already hurried visits may not be practical, and some components (e.g., genetic screening or laboratory testing) may not be indicated for every woman. Absence of any preconception care will miss all of those pregnancies that are unintended at the time of conception (50% in the United States) but are continued despite a lack of planning.
In order to address these issues, Before Pregnancy is available electronically at StudentConsult.com and may be used to evaluate women who are planning a pregnancy. This type of preconception care should be started, especially in high-risk women (e.g., women with obesity, diabetes, or hypertension), 6 months to 1 year before conception is attempted. A more ambitious goal is for all women to participate, because not all “at risk” women will be identified by obvious existing comorbidities.
Prenatal Care
The three basic components of prenatal care are (1) early and continuing risk assessment, (2) health promotion, and (3) medical and psychosocial interventions and follow-up. Risk assessment includes a complete history, a physical examination, laboratory tests, and assessment of gestational age and well-being of the mother and her fetus(es). Health promotion consists of providing information on proposed care, enhancing general knowledge of pregnancy and parenting, and promoting and supporting healthful behaviors. Interventions include the management and treatment of any existing illness, provision of social and financial resources if required, and referral to and consultation with other specialized providers.
The First Prenatal Visit
The first prenatal visit provides an opportunity to review medical, reproductive, family, genetic, nutritional, and psychosocial histories. Women whose health may be seriously jeopardized by the pregnancy, such as those with Eisenmenger syndrome or a history of peripartum cardiomyopathy, should be counseled about the option of terminating the pregnancy. Reproductive histories that include preterm birth, low birth weight, preeclampsia, stillbirth, congenital anomalies, and gestational diabetes are important to record because of the substantial risk of recurrence. Women with prior cesarean delivery should be asked about the circumstances of the delivery, and discussion about options for the mode of delivery for the current pregnancy should be initiated. Additionally, the importance of screening women for domestic violence cannot be overemphasized. As many as 8-10% of pregnant women are physically abused during pregnancy, making domestic violence more common than preeclampsia, diabetes, IUGR, and preterm birth.
Standardized forms have been developed to facilitate overall prenatal risk assessment, and this technology has been incorporated into electronic health records at some institutions. A complete physical examination should be performed including assessment of the patient's body mass index (BMI). A woman's BMI can increase between pregnancies by 20-30% because of excessive weight gain in the first pregnancy. Clinicians should be familiar with physical findings associated with normal pregnancy, such as systolic murmurs, exaggerated splitting and S 3 during cardiac auscultation, or spider angiomata, palmar erythema, linea nigra, and striae gravidarum on inspection of the skin. During the breast examination, clinicians should initiate discussion about breastfeeding. A pelvic examination should be performed, and the appearance and length of the cervix and the status of the last Papanicolaou (Pap) smear should be documented, or a new Pap smear obtained.
Prenatal laboratory testing should be undertaken as outlined in Table 7-1 if not done during preconception care. Screening for, and treatment of asymptomatic bacteriuria significantly reduces the risk of pyelonephritis and preterm delivery.
Women who are Rh negative should receive Rh O (D) immune globulin (Rh O -GAM) at 28 weeks' gestation and postpartum, and at any point of care when sensitization may occur (e.g., threatened abortion or invasive procedures such as amniocentesis and chorionic villus sampling [CVS]). Rubella vaccination is contraindicated during pregnancy, and pregnant women who are found to be seronegative should be vaccinated immediately postpartum. Testing for syphilis is mandated by law in virtually all states. Early diagnosis and treatment of syphilis can reduce perinatal morbidity. Women who test negative for hepatitis B surface antigen and are at high risk for hepatitis B infection (e.g., health care workers) are candidates for vaccination before and during pregnancy. Infants born to women who test positive for hepatitis B surface antigen should receive both hepatitis B immune globulins (HBIG) and hepatitis B vaccine within 12 hours of birth, followed by two more injections of hepatitis B vaccine in the first 6 months of life. With the increasing incidence of whooping cough (pertussis) and serious complications in young children, secondary vaccination with Tdap (tetanus, diphtheria and acellular pertussis) vaccine should be given, ideally between 27 and 36 weeks of pregnancy.
Voluntary and confidential human immunodeficiency virus (HIV) counseling and testing should be offered and documented in the medical record. Diagnosis and treatment significantly reduce the risk of vertical transmission. Other tests such as screening for sexually transmitted infections (STIs) like gonorrhea and chlamydia are generally considered routine. All pregnant women at high risk for tuberculosis (TB) should be screened with a purified protein derivative (PPD) skin test when they begin prenatal care. For women who have received BCG (bacillus Calmette-Guérin) immunization (which can cause a positive test in the absence of TB), a blood test is available called the Interferon Gamma Release Assay (IGRA). A positive test implies that the person has been infected with TB bacteria. HIV and other perinatal (TORCH) infections are also discussed in Chapter 22 .
Additionally, the clinician should use the first prenatal visit to confirm pregnancy and determine viability, estimate gestational age and due date, diagnose and deal with early pregnancy loss, provide genetic counseling and information about teratology, and provide advice on alleviating unpleasant symptoms during pregnancy. Information about nutrition, behavioral changes to expect, and the benefits of breastfeeding should be provided as prenatal care progresses. Clinical pelvimetry should be performed sometime before labor begins (see Chapter 8 ).
Confirming Pregnancy and Determining Viability
About 30-40% of all pregnant women will have some bleeding during early pregnancy (e.g., implantation bleeding ), which may be mistaken for a period. Therefore, a pregnancy test should be performed in all women of reproductive age who present with abnormal vaginal bleeding.
The pregnancy test detects human chorionic gonadotropin (hCG) in the serum or the urine. The most widely used standard is the First International Reference Preparation (1st IRP). The hCG molecule is first detectable in serum 6 to 8 days after ovulation. A titer of less than 5 IU/L is considered negative, and a level above 25 IU/L is a positive result. Values between 6 and 24 IU/L are considered equivocal, and the test should be repeated in 2 days. A concentration of about 100 IU/L is reached about the date of expected menses. Most qualitative urine pregnancy tests can detect hCG above 25 IU/L.
It is important to differentiate a normal pregnancy from a nonviable or ectopic gestation. In the first 30 days of a normal gestation, the level of hCG doubles every 2.2 days. In patients whose pregnancies are destined to abort, the level of hCG rises more slowly, plateaus, or declines.
The use of transvaginal ultrasonography has improved the accuracy of predicting viability in early pregnancies. Using transvaginal ultrasonography, the gestational sac should be seen at 5 weeks' gestation or a mean hCG level of about 1500 IU/L (1st IRP). The fetal pole should be seen at 6 weeks or a mean hCG level of about 5200 IU/L. Fetal cardiac motion should be seen between 6 and 7 weeks or a mean hCG level of about 17,500 IU/L. The presence of a gestational sac of 8 mm (mean sac diameter) without a demonstrable yolk sac, 16 mm without a demonstrable embryo, or the absence of fetal cardiac motion in an embryo with a crown-rump length of greater than 5 mm indicates probable embryonic demise. When there is any doubt about these measurements, it is best to repeat the evaluation in 1 week before terminating the pregnancy. Using pulse wave Doppler of the heart to determine heart rate is not recommended.
Incidence of Early Pregnancy Loss
Because the incidence of conception is unknown, the incidence of spontaneous abortion (miscarriage) cannot be determined with certainty. Spontaneous abortion occurs in 10-15% of clinically recognizable pregnancies. The term biochemical pregnancy refers to the presence of hCG in the blood of a woman 7 to 10 days after ovulation but in whom menstruation occurs when expected. In other words, conception has occurred, but spontaneous loss of the gestation takes place without prolongation of the menstrual cycle. When both clinical and biochemical pregnancies are considered, evidence would suggest that more than 50% of all conceptions are lost, the majority in the 14 days following conception.
Real-time ultrasonography has been used extensively to monitor the intrauterine events of the first trimester of pregnancy. If a live, appropriately growing fetus is present at 8 weeks' gestation, the fetal loss rate over the next 20 weeks (up to 28 weeks) is in the order of 3%.
Types of Spontaneous Abortion
The terms and definitions in the remainder of this chapter refer only to clinically recognizable pregnancies.
Threatened Abortion
The term threatened abortion is used when a pregnancy is complicated by vaginal bleeding before the 20th week. Pain may not be a prominent feature of threatened abortion, although a lower abdominal dull ache sometimes accompanies the bleeding. Vaginal examination at this stage usually reveals a closed cervix. Approximately one-third of pregnant women have some degree of vaginal bleeding during the first trimester, and 25-50% of threatened abortions eventually result in loss of the pregnancy. Current research suggests that there is a continuum of risk between threatened abortion and preterm birth. Thus, the use of ultrasound to assess the location of the placenta and the length of the cervix may provide a baseline to help assess changes after 20 weeks, and may help formulate a plan of management to prevent early preterm birth (see Chapter 12 ).
Inevitable Abortion
In the case of inevitable abortion, a clinical pregnancy is complicated by both vaginal bleeding and cramp-like lower abdominal pain. The cervix is frequently partially dilated, contributing to the inevitability of the process.
Incomplete Abortion
In addition to vaginal bleeding, cramp-like pain, and cervical dilation, an incomplete abortion involves the passage of some of the products of conception, often described by the woman as looking like pieces of skin or liver.
Complete Abortion
In complete abortion, after passage of all the products of conception, the uterine contractions and bleeding abate, the cervix closes, and the uterus is smaller than the period of amenorrhea would suggest. Ultrasound can be used to assess the presence of retained placental tissue if excessive bleeding continues. In addition, the symptoms of pregnancy are no longer present, and the pregnancy test becomes negative.
Missed Abortion
The term missed abortion is used when the fetus has died but is retained in the uterus, usually for more than 6 weeks. Because coagulation problems may develop, fibrinogen levels should be checked weekly until the fetus and placenta are expelled (spontaneously) or removed surgically.
Recurrent Abortion
Three successive spontaneous abortions usually occur before a patient is considered to be a recurrent aborter. Many clinicians feel that two successive first-trimester losses or a single second-trimester spontaneous abortion is justification for an evaluation of a couple for the cause(s) of the pregnancy losses (see genetic evaluation section that follows).
Etiology of Recurrent Abortion
Although many factors may result in the loss of a single pregnancy, relatively few factors are present consistently in couples who abort recurrently. Cause and effect relationships in individual patients are frequently difficult to determine.
General Maternal Factors
Infection
Mycoplasma, Listeria, or Toxoplasma should be specifically sought in women with recurrent abortions because despite being found infrequently, they are all treatable with antibiotics (see Chapter 22 ).
Smoking and Alcohol
Maternal smoking and alcohol consumption are associated with an increased incidence of chromosomally abnormal abortions. Women who smoke 20 or more cigarettes daily and consume more than seven standard alcoholic drinks per week have a fourfold increase in their risk of spontaneous abortion. There is a doubling of the risk of spontaneous abortion with as little as two drinks a week.
Psychosocial Stress
Domestic violence and other forms of stress are associated with a greater risk of pregnancy complications such as spontaneous abortion, preterm birth, and low birth weight.
Medical Disorders
Diabetes mellitus, hypothyroidism, and systemic lupus erythematosus (SLE) are associated with recurrent pregnancy loss. The evidence linking diabetes mellitus with spontaneous abortion is not conclusive, and severe hypothyroidism is more often associated with disordered ovulation than spontaneous abortion. Up to 40% of clinical pregnancies are lost in women with SLE, and such patients have an increased risk of pregnancy loss before developing the clinical stigmata of the disease (see Chapter 16 ).
Maternal Age
If a live fetus is demonstrated by ultrasonography at 8 weeks' gestational age, fewer than 2% of these pregnancies will abort spontaneously when the mother is younger than 30 years of age. If, however, she is older than 40 years, the risk exceeds 10%, and it may be as high as 50% at age 45 years. The probable explanation is the increased incidence of chromosomally abnormal fetuses in older women.
Local Maternal Factors
Uterine abnormalities, including cervical incompetence, congenital abnormalities of the uterine fundus (as may result from gestational exposure to diethylstilbestrol) and acquired abnormalities of the uterine fundus, are known to be associated with pregnancy loss.
Cervical incompetence occurs under a number of circumstances but is usually the result of trauma. This occurs most frequently from mechanical dilation of the cervix at the time of termination of pregnancy, but it may also occur at the time of diagnostic curettage. The diagnosis of cervical incompetence is usually made when a mid-trimester pregnancy is lost with a clinical picture of sudden unexpected rupture of the membranes, followed by painless expulsion of the products of conception.
There continues to be controversy surrounding cervical incompetence, with some experts suggesting that cervical incompetence is, in most instances, a variant of preterm delivery, occurring at a time when there is an associated finding of asymptomatic ascending infection. The question today in terms of the etiology is what comes first. Is it infection that causes the problem or is it some form of metabolic dysregulation that can be identified early and treated to prevent these changes? Chapter 12 covers newer concepts of the cause(s) of early pregnancy loss and preterm birth.
When cervical incompetence is suspected during pregnancy (e.g., history of cervical incompetence in a previous pregnancy or of cone biopsy of the cervix), sequential ultrasonography of the cervix indicating funneling or shortness of the cervix or widening of the lower uterine segment may identify the problem before a pregnancy loss occurs.
A congenitally abnormal uterus may be associated with pregnancy loss in both the first and the second trimesters. Surgical correction of the abnormality, particularly with a history of second trimester loss, is frequently successful. Complete evaluation of the congenitally abnormal uterus usually requires laparoscopic, hysteroscopic, and hysterographic examination before any management plan can be made.
The most commonly acquired abnormalities of the uterus with the potential to affect fecundity are submucous fibroids. Although these tend to occur more frequently in women in their late 30s, they should be considered when investigating pregnancy loss in all women. Removal of submucous fibroids and intramural fibroids larger than 6 cm are associated with improved fecundity, especially when there is distortion of the endometrial cavity. Subserous fibroids do not appear to affect fecundity.
Intrauterine adhesions result from trauma to the basal layer of the endometrium from previous surgery or infection. When most of the uterine cavity has been obliterated (Asherman syndrome), amenorrhea results. More frequently, fewer intrauterine adhesions (synechiae) are present, menses are reasonably normal, and the lesions are not even suspected until a pregnancy is attempted and lost. Surgical correction of these intrauterine adhesions is recommended to improve fecundity.
Fetal Factors
The most common cause of spontaneous abortion is a significant genetic abnormality of the conceptus. In spontaneous first-trimester abortions, approximately two-thirds of fetuses have significant chromosomal anomalies, with approximately half of these being autosomal trisomies and the majority of the remainder being triploid, tetraploid, or 45,X monosomies. Fortunately, the majority of these are not inherited from either mother or father and are single nonrecurring events. When seen on ultrasonography before spontaneous abortion, many such pregnancies appear to consist of an empty gestational sac. When a fetus is present in many late first-trimester and early second-trimester abortions, it is often significantly abnormal, either genetically or morphologically. It seems that nature has a way of identifying some of its major mistakes and causing them to abort.
Placental Factors
The fetus and placenta interact in terms of genetic and neuroendocrine differences. For example, the placental genetic structure is composed of genes from the mother, the father, and even imprinted genes from the parents of both the mother and father. How these interact and support normal development and specific diseases is the subject of intense investigation. For example the placenta expresses an enzyme 11β-hydroxylase that converts cortisol to inactive corticosterone, which protects the fetus from excessive cortisol when the mother is stressed. This enzyme is not turned on until 22 to 24 weeks, thus leaving the fetus at risk from maternal stress before this gestational age. In addition, genetic polymorphisms have been identified that limit the amount of this enzyme produced, thus rendering the fetus at risk after 22 to 24 weeks.
Women with obesity during pregnancy have a greater risk of developing leptin (a placental peptide) resistance that leads to a greater risk of fetal IUGR, which in turn programs the fetus for obesity during childhood. Thus, it is important for the student to develop a sound understanding of the role of the placenta in fetal and maternal health.
Chromosomal Factors
Occasionally, fetal chromosomal abnormalities occur as a result of a chromosomal rearrangement (balanced translocation or inversion) in either or both parents. Therefore, karyotyping is important for evaluation of couples suffering from recurrent abortion.
Immunologic Factors
A successful pregnancy depends on a number of immunologic factors that allow the host (mother) to retain a genetically foreign product (fetus) without rejection taking place (see Chapter 6 ). The precise mechanism of this immunologic anomaly is not fully understood, but the immunologic functioning of some women as explained in more detail in Chapter 6 , particularly those who abort recurrently or those who deliver prematurely, is different from that of women who carry pregnancies to term. Briefly the innate immune system is activated in early pregnancy with the production of specific cytokines that prevent early rejection of the fetus. Subsequently during the second half of pregnancy the adaptive portion of the immune system is activated to downregulate the innate immune system to support the developing fetus.
Management
Threatened Abortion
A threatened abortion is best managed by an ultrasonic examination to determine the viability of the fetus. Of those in whom a live fetus is present, 94% will produce a live baby, although the incidence of preterm delivery in these cases may be somewhat higher than in those who do not bleed in the first trimester. Once a live fetus has been demonstrated to the couple on ultrasonography, management consists essentially of reassurance; however they should be encouraged to undergo first-trimester screening for chromosomal abnormalities such as trisomy 13, 18, or 21. There is no need for admission to hospital, nor is there any evidence that bed rest improves the prognosis; however, psychosocial support is important. Recently, there has been evidence that women with vitamin D deficiency are at increased risk of spontaneous abortion, preterm birth and stillbirth. The mechanism is thought to be related to abnormal uterine muscle function (see Chapter 11 ).
Incomplete Abortion
Until bleeding has stopped or is minimal, it is best to insert an intravenous line and take blood for grouping and cross-matching, as shock may occur from hemorrhage or sepsis. Once the patient's condition is stable, the remaining products of conception should be evacuated from the uterus using appropriate pain control. These tissues should be sent for pathologic evaluation. An incomplete abortion that is infected must be managed vigorously. Delay in treatment may result in overwhelming sepsis that may lead to excessive hemorrhage, renal and hepatic failure, disseminated intravascular coagulation (DIC), and rarely, death.
Missed Abortion
Suspected missed abortion should be confirmed by ultrasound to minimize the risk of sepsis and DIC, and to reduce the extent of hemorrhage and the degree of pain that accompanies the spontaneous expulsive process. In some studies vitamin D deficiency has been associated with early pregnancy loss. A proposed mechanism is that women with vitamin D deficiency have an altered immune system. Macrophages do not make the antibacterial peptide cathelicidin, which is important in reducing the risk of infection, as well as contributing to abnormal muscular function.
General Management Considerations
When the patient is Rh negative and does not have Rh (anti-D) antibodies, prophylactic Rh O -GAM should be administered (see Chapter 15 ). All couples that have had a pregnancy loss should be seen and counseled some weeks after the event. At that time, questions that the couple may have can be answered, the findings of any pathologic studies discussed, and reassurance given about their chances of reproductive success in the future.
Recurrent Abortion
As far as the mother is concerned, it is appropriate to rule out the presence of systemic disorders such as diabetes mellitus, SLE, and thyroid disease, and it is also necessary to test for the presence of a lupus anticoagulant. Paternal and maternal chromosomes should be evaluated, and hysteroscopy or hysterography should be performed to evaluate the uterine cavity.
Over half of couples with recurrent losses will have normal findings during the standard evaluation. With the information now available on the role of vitamin D in the health of women, it is recommended that women also be assessed for vitamin D deficiency.
When a specific etiologic factor is found, appropriate management often leads to reproductive success. Many of the congenital abnormalities of the uterus can now be diagnosed using pelvic ultrasonography and may no longer require laparotomy for repair. Cervical incompetence is managed by the placement of a cervical suture (cerclage) at the level of the internal os; this suture is best placed in the first trimester, once a live fetus has been demonstrated on ultrasonography. The effectiveness of prophylactic cervical cerclage in preventing recurrent loss from cervical incompetence has not been conclusively established (see Chapter 17 ).
Estimating Gestational Age and Date of Confinement
Gestational age should be determined during the first prenatal visit. Accurate determination of gestational age may become important later in pregnancy for the management of obstetric conditions such as preterm labor, IUGR, and postdate pregnancy. Clinical assessment to determine gestational age is usually appropriate for the woman with regular menstrual cycles and a known last menstrual period that was confirmed by an early examination. Estimated date of confinement (EDC) or “due date” may be determined by adding 9 months and 7 days to the first day of the last menstrual period.
Ultrasonography may also be used to estimate gestational age. Measurement of fetal crown-rump length between 6 and 11 weeks' gestation can define gestational age to within 7 days. At 12 to 20 weeks, gestational age can be determined within 10 days by the average of multiple measurements (e.g., biparietal diameter, femur length, abdominal and head circumferences). Thereafter, measurements become less reliable with advancing gestation (±3 weeks in the third trimester).
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