Essentials of Prenatal care
The first prenatal visit should occur as early as possible after the diagnosis of pregnancy and should include the following: history, physical examination, laboratory tests, advice to patients, and tests and procedures.
Age, ethnic background, occupation. Onset of LMP and its normality, possible conception dates, bleeding after LMP, medical history, all prior pregnancies (duration, outcome, and complications), symptoms of present pregnancy. Use of drugs, alcohol, tobacco, caffeine, nutritional habits (Table 18-1). Family history of congenital anomalies and heritable diseases. History of childhood varicella. Prior STDs or risk factors for HIV infection.
Height, weight, blood pressure, general physical examination. Abdominal and pelvic examination: (1) estimate uterine size or measure fundal height; (2) evaluate bony pelvis for symmetry and adequacy; (3) evaluate cervix for structural anatomy, infection, effacement, dilation; (4) detect fetal heart sounds by Doppler device after 10 weeks or fetoscope after 18 weeks.
Urinalysis, culture of a clean-voided midstream urine sample, complete blood count with red cell indices, serologic test for syphilis, rubella antibody titer, blood group, Rh type, atypical antibody screening, and HBsAg evaluation. Human immunodeficiency virus (HIV) screening should be offered to all pregnant women. Cervical cultures are usually obtained for Neisseria gonorrhoeae and chlamydia, along with a Papanicolaou smear of the cervix. All black women should have sickle cell screening. Women of African, Asian, or Mediterranean ancestry with anemia or low MCV values should have hemoglobin electrophoresis performed to identify abnormal hemoglobins (Hb S, C, F, a-thalassemia, ß-thalassemia). Tuberculosis skin testing is indicated for immigrant and inner city populations. Genetic counseling with the option of chorionic villus sampling or genetic amniocentesis should be offered to all women who will be 35 years of age or older at delivery and those who have had prior offspring with chromosomal abnormalities. Tay-Sachs blood screening is offered to Jewish women with Jewish partners. Screening for cystic fibrosis is offered to all pregnant women. Hepatitis C antibody screening should be offered only to those pregnant women who are at high risk of infection.
Pregnant women who work in medical-dental health care or the police and fire departments and those who are household contacts of a hepatitis B virus carrier or a hemodialysis patient and are HBsAg-negative at prenatal screening are at high risk of acquiring hepatitis B. They should be vaccinated during pregnancy.
Advice to Patients
A. Prenatal Visits
Prenatal care should begin early and maintain a schedule of regular prenatal visits: 0-28 weeks, every 4 weeks; 28-36 weeks, every 2 weeks; 36 weeks on, weekly.
Eat a balanced diet containing the major food groups.
Take prenatal vitamins with iron and folic acid.
Expect to gain 20-40 lb. Do not diet to lose weight during pregnancy.
Decrease caffeine intake to 0-1 cup of coffee, tea, or caffeinated cola daily.
Avoid eating raw or rare meat, and wash hands after handling raw meat.
Eat fresh fruits and vegetables and wash them before eating.
Do not take medications unless prescribed or authorized by your provider.
D. Alcohol and Other Drugs
Abstain from alcohol, tobacco, and all recreational (“street”) drugs. No safe level of alcohol intake has been established for pregnancy. Fetal effects are manifest in the fetal alcohol syndrome, which includes growth restriction, facial abnormalities, and serious central nervous system dysfunction. These effects are thought to result from direct toxicity of ethanol itself as well as of its metabolites such as acetaldehyde. Characteristic findings include shortened palpebral fissures, low-set ears, midfacial hypoplasia, a smooth philtrum, a thin upper lip, microcephaly, mental retardation, and attention deficit disorder. Skeletal and cardiac abnormalities may also be seen.
Cigarette smoking results in fetal exposure to carbon monoxide and nicotine, and this is thought to eventuate in a number of adverse pregnancy outcomes. An increased risk of abruptio placentae, placenta previa, and premature rupture of the membranes is documented among women who smoke. Premature delivery occurs 20% more frequently among smoking pregnant women, and the birth weights of their infants are on average 200 g lower than infants of nonsmokers. Women who smoke should quit smoking or at least reduce the number of cigarettes smoked per day to as few as possible. Pregnant women should also avoid exposure to environmental smoke (“passive smoking”).
Sometimes compounding the above effects on pregnancy outcome are the independent adverse effects of illicit drugs. Cocaine use in pregnancy is associated with an increased risk of premature rupture of membranes, preterm delivery, placental abruption, intrauterine growth restriction, neurobehavioral deficits, and sudden infant death syndrome. Similar adverse pregnancy effects are associated with amphetamine use, perhaps reflecting the vasoconstrictive potential of both amphetamines and cocaine. Adverse effects associated with opioid use include intrauterine growth restriction, prematurity, and fetal death.
E. X-Rays and Noxious Exposures
Avoid x-rays unless essential and approved by a physician. Inform your dentist and your providers that you are pregnant. Avoid chemical or radiation hazards. Avoid excessive heat in hot tubs or saunas. Avoid handling cat feces or cat litter. Wear gloves when gardening.
F. Rest and Activity
Obtain adequate rest each day. Abstain from strenuous physical work or activities, particularly when heavy lifting or weight bearing is required. Exercise regularly at a mild to moderate level. Avoid exhausting or hazardous exercises or new athletic training programs during pregnancy. Heart rate should be kept below 140 beats/min during exercise.
G. Birth Classes
Enroll with your partner in a childbirth preparation class well before your due date.
Tests & Procedures
A. Each Visit
Weight, blood pressure, fundal height, fetal heart rate, urine specimen for protein and glucose. Review patient’s concerns about pregnancy, health, and nutrition.
B. 6-12 Weeks
Confirm uterine size and growth by pelvic examination. Document fetal heart tones (audible at 10-12 weeks of gestation by Doppler). Transvaginal chorionic villus sampling (CVS) between 10 and 12 weeks when indicated or screening for trisomy 18, 21, and cardiac defects using nuchal translucency measurement on sonography, hCG, and pregnancy-associated plasma protein-A (PAPP-A).
C. 12-18 Weeks
Genetic counseling for women age 35 years or older at EDC and those with a family history of congenital anomalies or a previous child with a chromosomal abnormality, metabolic disease, or neural tube defect. Amniocentesis is performed as indicated and requested by the patient.
D. 12-24 Weeks
Fetal ultrasound examination to determine pregnancy dating and evaluate fetal anatomy. An earlier examination provides the most accurate dating, and a later examination demonstrates fetal anatomy in greater detail. The best compromise is at 18-20 weeks of gestation.
E. 16-20 Weeks
Maternal serum a-fetoprotein testing is offered to all women to screen for neural tube defects. In some states, such testing is mandatory. Serum a-fetoprotein is usually combined with measurement of estriol and hCG (triple screen) for the detection of fetal Down’s syndrome.
F. 20-24 Weeks
Instruct patient in symptoms and signs of preterm labor and rupture of membranes.
G. 24 Weeks to Delivery
Ultrasound examination is performed as indicated. Typically, fetal size and growth are evaluated when fundal height is 3 cm less than or more than expected for gestational age. In multiple pregnancies, ultrasound should be performed every 4 weeks to evaluate for discordant growth.
H. 26-28 Weeks
Screening for gestational diabetes by a 50-g glucose load (Glucola) and a 1-hour post-Glucola blood glucose determination. Abnormal values should be followed up with a 3-hour glucose tolerance test (Table 18-3).
I. 28 Weeks
If initial antibody screen is negative, repeat antibody testing for Rh-negative patients, but result is not required before Rho(D) immune globulin is administered.
J. 28-32 Weeks
Repeat the complete blood count to evaluate for anemia of pregnancy.
K. 28 Weeks to Delivery
Determination of fetal position and presentation. Question the patient at each visit for symptoms or signs of preterm labor or rupture of membranes. Assess maternal perception of fetal movement at each visit. Antepartum fetal testing is performed as medically indicated.
L. 36 Weeks to Delivery
Repeat syphilis and HIV testing, cervical cultures for N gonorrhoeae, and Chlamydia trachomatis in at-risk patients. Discuss with the patient the indicators of onset of labor, admission to hospital, management of labor and delivery, and options for analgesia and anesthesia. Weekly cervical examinations are not necessary unless indicated to assess a specific clinical situation. Elective delivery (whether by induction or cesarean section) prior to 39 weeks of gestation requires confirmation of fetal lung maturity.
The CDC has recommended universal prenatal culture-based screening for group B streptococcal colonization in pregnancy. A single standard culture of the distal vagina and anorectum is collected at 35-37 weeks. No prophylaxis is needed if the screening culture is negative. Patients whose cultures are positive receive intrapartum penicillin prophylaxis with labor. Patients with risk factors such as a previous infant with invasive group B streptococcal disease, or group B streptococcal bacteriuria during the pregnancy, or delivery at less than 37 weeks of gestation also receive intrapartum prophylaxis. Patients whose cultures at 35-37 weeks were not done or whose results are not known receive prophylaxis only with the risk factors of intrapartum temperature greater than 38 °C or membrane rupture greater than 18 hours.
The routine recommended regimen for prophylaxis is penicillin G, 5 million units intravenously as a loading dose and then 2.5 million units intravenously every 4 hours until delivery. In penicillin-allergic patients not at high risk for anaphylaxis, one should give cefazolin 2 g intravenously as an initial dose and then 1 g intravenously every 8 hours until delivery. In patients at high risk for anaphylaxis, use vancomycin 1 g intravenously every 12 hours until delivery or, after confirmed susceptibility testing of group B streptococcal isolate, clindamycin 900 mg intravenously every 8 hours or erythromycin 500 mg intravenously every 6 hours until delivery.
M. 41 Weeks and Beyond
Examine the cervix to determine the probability of successful induction of labor. Based on this, induction of labor is undertaken if the cervix is favorable (generally, cervix = 2 cm dilated = 50% effaced, vertex at -1 station, soft cervix, and midposition); if unfavorable, antepartum fetal testing is begun.
Schrag S et al: Prevention of perinatal group B streptococcal disease. Revised guidelines from CDC. MMWR Recomm Rep 2002;51(RR-11):1.
Vintzileos AM et al: The impact of prenatal care in the United States on preterm births in the presence and absence of antenatal high-risk conditions, Am J Obstet Gynecol, 2002; 187:1254.
Revision date: July 6, 2011
Last revised: by Jorge P. Ribeiro, MD
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