Routine Prenatal Care: First Trimester

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Chapter 181 Routine Prenatal Care: First Trimester

THE CHALLENGE

Despite the dramatic and vulnerable changes that the conceptus undergoes in the first 14 weeks of gestation, many patients are unaware of their pregnancy or delay seeking prenatal care. Emerging evidence suggests that it is during this period the foundations of a successful pregnancy and even the future health of the adult individual are set. Although most pregnant women would deliver healthy infants without any prenatal care, obstetric care is designed to promote optimal health throughout the course of normal pregnancy while screening for and managing any complications that may develop.
Scope of the Problem: Roughly one fourth of pregnant women do not receive care during the first trimester.
Objectives of Management: To protect the health and well-being of mother and fetus.

TACTICS

Relevant Pathophysiology: During the first trimester of gestation, the developing embryo implants in the endometrium (except in the case of ectopic pregnancies), the placental attachment to the mother is created, and the major structures and organs of the body are formed. The developing embryo is sensitive to exposures to toxins, medications, and radiation and the effects of maternal conditions that can disrupt this process. Errors in this process may result in major disruptions in structure or function of the fetus or even the complete loss of the pregnancy.
About the 12th week of gestation, the placenta takes over hormonal support for the pregnancy from the corpus luteum. If this transition does not happen smoothly, the pregnancy can be lost.
Strategies: At the first prenatal visit, a comprehensive history should be taken, including previous pregnancy outcome(s), if any, and any medical or surgical conditions that may affect pregnancy. This should include past medical history, information pertinent to genetic screening, and any events in the course of the current pregnancy. Special attention should also be given to diet, tobacco or alcohol use, and any medications or substances used. Routine laboratory studies should be ordered, and the patient should be given instructions concerning routine prenatal care, warning signs of complications, and who to contact with questions or problems. A complete physical examination should be performed, including a Pap test and tests for sexually transmitted diseases.
It is important early in the course of pregnancy to establish an accurate gestational age and estimated date of confinement (EDC, or due date). This information is needed to manage later complications of pregnancy and to determine the timing of evaluations (e.g., neural tube screening, 1-hour glucose challenge testing, Rh prophylaxis). If needed, transvaginal and transabdominal ultrasonographic techniques allow gestational age determination with approximately 7- to 10-day accuracy when performed during the first trimester.
At each visit, the patient should be asked about any problems such as vaginal bleeding, nausea/vomiting, dysuria, or vaginal discharge. Each prenatal visit should include measurements of blood pressure and weight and an assessment for edema. (Blood pressure generally declines at the end of the first trimester, increasing again in the third trimester.) A clean-catch urine sample should be tested (most often by dipstick) for protein and signs of infection. Obstetric assessments should include uterine size by pelvic examination or fundal height measurement and documentation of the presence and rate of fetal heart tones by the use of a fetal Doppler ultrasound device. (The fetal heart may not be routinely detected by a Doppler device until 12 weeks or later.)
Patients at low risk may be followed at 4-week intervals until 28 weeks of gestation.
Patient Education: American College of Obstetricians and Gynecologists Patient Education Booklet AP001 (Nutrition During Pregnancy), AB005 (You and Your Baby: Prenatal Care, Labor and Delivery, and Postpartum Care), AP032 (Especially for Fathers), AP060 (Later Childbearing), AP090 (Early Pregnancy Loss: Miscarriage and Molar Pregnancy), AP0103 (Having a Baby [Especially for Teens]), AP104 (Drugs and Pregnancy), AP119 (Exercise During Pregnancy), AP126 (Morning Sickness), AP133 (Routine Tests in Pregnancy), AP156 (How Your Baby Grows During Pregnancy), AP165 (Screening Tests for Birth Defects), CP001 (Cystic Fibrosis Carrier Testing: The Decision Is Yours).

IMPLEMENTATION

Special Considerations: Between 4% and 8% of pregnant women are victims of “battering” and will benefit from counseling or help finding shelters and other social supports. (In the United States, suicide, homicide, and trauma associated with auto accidents where seat belts were not used account for three fourths of maternal mortality. These are all areas in which proactive counseling and assistance can have a positive impact on reducing morbidity or mortality.)

Commonly Ordered Initial Laboratory and Other Tests

• Complete blood count
• Urinalysis and urine culture and sensitivity
• Blood group, Rh, antibody screen
• Serologic test for syphilis (rapid plasma reagin [RPR], Venereal Disease Research Laboratory [VDRL])
• Human immunodeficiency virus (HIV) titer by enzyme-linked immunosorbent assay (ELISA); Western blot if HIV+ by ELISA
• Hepatitis B surface antigen
• Rubella titer
• Cervical cytology (Pap test)
• Cervical culture for Neisseria gonorrhoeae
• Hemoglobin electrophoresis (selected patients)
• Maternal serum screening for open neural tube defects (triple or quad screen) at 15 to 20 weeks (maternal serum alpha-fetoprotein plus other markers)

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If a genetic evaluation of the fetus is indicated, chorionic villus sampling may be performed between the 10th and 12th week of gestation. Screening for cystic fibrosis should be offered to all patients during either the first or second trimester.

REFERENCES

Level III

American Academy of Pediatrics, American College of Obstetricians and Gynecologists. Guidelines for perinatal care, 5th ed. Elk Grove Village, IL: AAP, 2002. Washington, DC, ACOG

American College of Obstetricians and Gynecologists. Prevention of Rh D alloimmunization. ACOG Practice Bulletin 4. Washington, DC: ACOG, 1999.

American College of Obstetricians and Gynecologists. Air travel during pregnancy. ACOG Committee Opinion 264. Obstet Gynecol. 2001;98:1187.

American College of Obstetricians and Gynecologists. Exercise during pregnancy and the postpartum period. ACOG Committee Opinion 267. Obstet Gynecol. 2002;99:171.

American College of Obstetricians and Gynecologists. Guidelines for women’s health care, 2nd ed. Washington, DC: ACOG, 2002.

American College of Obstetricians and Gynecologists. Thyroid disease in pregnancy. ACOG Practice Bulletin 37. Obstet Gynecol. 2002;100:387.

American College of Obstetricians and Gynecologists. Neural tube defects. ACOG Practice Bulletin 44. Obstet Gynecol. 2003;102:203.

American College of Obstetricians and Gynecologists. Guidelines for diagnostic imaging during pregnancy. ACOG Committee Opinion 299. Obstet Gynecol. 2004;104:647.

American College of Obstetricians and Gynecologists. Nausea and vomiting of pregnancy. ACOG Practice Bulletin 52. Obstet Gynecol. 2004;103:803.

American College of Obstetricians and Gynecologists. Ultrasonography in pregnancy. ACOG Practice Bulletin 58. Obstet Gynecol. 2004;104:1449.

American College of Obstetricians and Gynecologists. Management of alloimmunization during pregnancy. ACOG Practice Bulletin 75. Obstet Gynecol. 2006;108:457.

American College of Obstetricians and Gynecologists. Screening for fetal chromosomal abnormalities. ACOG Practice Bulletin 77. Obstet Gynecol. 2007;109:217.

Kogan MD, Martin JA, Alexander GR, et al. The changing pattern of prenatal care utilization in the United States, 1981–1995, using different prenatal care indices. JAMA. 1998;279:1623.

Mustard CA, Roos NP. The relationship of prenatal care and pregnancy complications to birthweight in Winnipeg, Canada. Am J Public Health. 1994;84:1450.

Prevention of neural tube defects. Results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group. Lancet. 1991;338:131.

Yu SM, Alexander GR, Schwalberg R, Kogan MD. Prenatal care use among selected Asian American groups. Am J Public Health. 2001;91:1865.

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