Comprehensive Guide to Obstetrics and Maternal-Fetal Medicine

Signs of Pregnancy

Pregnancy can be identified through a combination of positive, probable, and presumptive signs. Positive signs are definitive and include palpation of the fetus by a healthcare provider, visualization of the fetus via ultrasound, and fetal heart tones auscultated with a Doppler or fetoscope. Probable signs suggest pregnancy but are not conclusive; they include Goodell's sign (softening of the cervix), Chadwick's sign (bluish discoloration of the cervix and vagina), Hegar's sign (softening of the lower uterine segment), enlargement of the uterus, and a positive urine or serum HCG test. Presumptive signs are subjective and reported by the woman, such as amenorrhea, nausea, swollen and tender breasts, fatigue, and quickening (fetal movement felt by the mother).

Additional clinical milestones include:

- Fundal height at 12 weeks is above the synthesis pubis, and fetal heart tones can be heard with Doppler at 10-12 weeks.

- By 20 weeks, the fundus reaches the level of the umbilicus, and fetal heart tones are detectable with a fetoscope or stethoscope.

## Physiologic Changes in Pregnancy

Pregnancy induces significant maternal cardiovascular adaptations:

- Increased maternal heart rate and cardiac output to meet the metabolic demands of the fetus.

- Plasma volume expands, which may lead to a physiologic anemia of pregnancy due to dilution.

- Heart sounds become louder; an S3 gallop is common in about 80% of pregnant women, reflecting increased preload.

- A systolic ejection murmur grade 2-4 over the pulmonary and tricuspid areas is frequently heard.

Peripheral edema is considered normal due to increased vascular permeability and fluid retention. Pregnancy is a hypercoagulable state, especially after labor, increasing the risk of thromboembolic events.

## Beta Human Chorionic Gonadotropin (Beta HCG)

Produced by the early placenta (chorion) starting day 8-10 of pregnancy, Beta HCG is a critical marker for pregnancy detection.

- Normal doubling time: HCG levels double every 48 hours during the first 12 weeks, indicating a viable pregnancy.

- Abnormal patterns:

- In ectopic pregnancy, HCG levels are lower than normal, increase slowly, and do not double as expected.

- During inevitable abortion, HCG levels drop rapidly, and cervical dilation is evident on gynecologic exam.

Doubling time is a valuable indicator of early pregnancy viability but loses predictive value after the first trimester.

## Pregnancy Screening Tests

Screening during pregnancy involves multiple laboratory assessments to monitor maternal and fetal health:

### First Trimester (up to 13 weeks)

- Urinalysis (UA) and urine culture and sensitivity (C&S)

- Complete blood count (CBC)

- Infectious disease screening: Hepatitis B, Rubella, Varicella, RPR (syphilis), HIV

- Blood type and Rh factor

- Urinalysis: check for protein (≥1+ may suggest preeclampsia), leukocytes, nitrites, blood, and glucose.

- Urine culture at 11-12 weeks to detect asymptomatic bacteriuria.

### Second Trimester (16-20 weeks)

- Quad screen (16-20 weeks): measures alpha-fetoprotein (AFP), beta HCG, estriol, and inhibin-A (helps identify Down syndrome).

- Anatomy scan (18-20 weeks): detailed fetal structural assessment.

- Gestational diabetes screening at 24-28 weeks with a 1-hour glucose challenge test (non-fasting); if abnormal, proceed to a 3-hour glucose tolerance test.

### Third Trimester (after 28 weeks)

- Group B Streptococcus (GBS) screening between 35-37 weeks.

Additional Tests:

- Chorionic villus sampling (CVS) (11-12 weeks): tests fetal chromosomes/DNA for abnormalities.

- Amniocentesis (15-18 weeks): assesses for genetic disorders and neural tube defects.

## Gestational Diabetes Mellitus (GDM)

GDM is glucose intolerance first recognized during pregnancy, associated with increased risks such as neural tube defects, congenital heart disease, shoulder dystocia, preeclampsia, and neonatal hypoglycemia.

### Screening and Diagnosis

- Screen at first visit if risk factors are present.

- If not high-risk, screen at 24-28 weeks with:

- One-step method: 50g non-fasting glucose; if >140 mg/dL, proceed to a 100g 3-hour oral glucose tolerance test (OGTT).

- OGTT criteria: fasting <95 mg/dL, 1 hr <180 mg/dL, 2 hr <155 mg/dL, 3 hr <140 mg/dL; 2 or more abnormal readings confirm GDM.

### Management

- Lifestyle modifications: dietary control, physical activity (walking, swimming), and blood glucose monitoring 4-6 times daily.

- Medications: insulin is preferred; oral agents are used cautiously.

## Hypertension in Pregnancy

Classified based on severity:

- Mild: SBP 140-149 or DBP 90-99

- Moderate: SBP 150-159 or DBP 100-109

- Severe: SBP ≥160 or DBP ≥110

### Treatment Principles

- Severe hypertension requires urgent IV therapy with labetalol, hydralazine, or nifedipine.

- Target blood pressure: 130-150 systolic and 80-100 diastolic.

- Avoid teratogenic drugs like ACE inhibitors, angiotensin II receptor blockers, and direct renin inhibitors.

### Postpartum Hypertension

- BP peaks 3-6 days postpartum.

- Managed with oral antihypertensives, with modifications if breastfeeding (e.g., furosemide).

- Blood pressure should be rechecked within 72 hours if severe, or 7-10 days if non-severe.

### Preconception Management

- Stabilize blood pressure with safe medications: labetalol, nifedipine, hydralazine, methyldopa.

- Avoid ACE inhibitors, ARBs, and thiazide diuretics.

## Preeclampsia and Eclampsia

Most cases occur after 20 weeks gestation, typically in the late third trimester, but can occur up to 4 weeks postpartum.

### Diagnostic Criteria

- Hypertension: SBP >140 mm Hg or DBP >90 mm Hg.

- Proteinuria: >0.3 grams in 24-hour urine or 1+ dipstick.

- Edema: facial, periorbital, or extremity swelling.

- Rapid weight gain: 2-5 pounds/week.

### Clinical Features

- Preeclampsia: hypertension with proteinuria and edema.

- Eclampsia: preeclampsia with seizures.

### Management

- Delivery is the definitive cure.

- Monitoring and managing blood pressure, preventing seizures with magnesium sulfate, and fetal surveillance are essential.

## Urinary Tract Infections in Pregnancy

UTIs are common and increase risks for preterm birth and low birth weight.

- Acute cystitis presents with dysuria, frequency, urgency, and nocturia.

- Asymptomatic bacteriuria requires treatment to prevent pyelonephritis.

### Diagnosis

- Based on urinalysis and urine culture.

- Positive dipstick (white blood cells, nitrites) warrants culture.

### Treatment

- Safe antibiotics include amoxicillin, cephalosporins (ceftriaxone, cefuroxime, cefazolin), erythromycin, and azithromycin.

- Nitrofurantoin is safe in early and mid-pregnancy but contraindicated late in pregnancy.

- Sulfa drugs are avoided in late pregnancy due to hemolytic risk.

- Monurol (fosfomycin) is a one-dose option safe in all trimesters.

- Pyelonephritis requires immediate ER referral.

## Placenta Previa and Placental Abruption

### Placenta Previa

- The placenta partially or completely covers the cervix.

- Presents as painless vaginal bleeding after 20 weeks, often triggered by intercourse.

- Ultrasound confirms diagnosis.

### Placental Abruption

- Premature detachment of the placenta from the uterine wall, usually in the 2nd or 3rd trimester.

- Symptoms include severe abdominal pain, vaginal bleeding, and contractions.

- Ultrasound is diagnostic.

## Vaccines During Pregnancy

- Tdap: recommended between 27-36 weeks each pregnancy to protect against pertussis.

- Influenza: safe after first trimester; vaccination during flu season is advised.

- Hepatitis B and A: given if not previously vaccinated or traveling to endemic areas.

- RSV (Abrysvo): administered 32-36 weeks during RSV season if the baby is expected to be born 2 weeks after vaccination.

### Contraindicated Vaccines

- Live vaccines such as MMR, varicella, smallpox, and BCG are contraindicated during pregnancy due to teratogenic risks.

## Prescribing and Medications in Pregnancy

### Safe Medications

- Acetaminophen: safe for pain and fever.

- Levothyroxine: safe for hypothyroidism.

- Insulin: preferred for diabetes management.

- Prenatal vitamins and folic acid: essential for fetal development.

- Antacids (Tums, Maalox): safe for reflux.

- Colace: safe laxative.

### Cautiously Used or Avoided Drugs

- NSAIDs: limited to specific indications; avoid in late pregnancy due to risk of premature closure of fetal ductus arteriosus.

- Decongestants: intranasal oxymetazoline preferred; pseudoephedrine avoided in first trimester.

- Antihistamines: chlorpheniramine and diphenhydramine are safest; newer agents are reassuring but less established.

### Antibiotics

- Penicillins (amoxicillin), cephalosporins, and macrolides (erythromycin, azithromycin) are safe, clarithomycin is the only macrolide that needs to be avoided in pregnancy.

- Nitrofurantoin: safe 1st and 2nd trimester; avoid in 3rd trimester

- Sulfa drugs: avoid pregnancy.

- Fluoroquinolones and tetracyclines: contraindicated due to fetal risks.

### Absolute Contraindications

- Accutane, Proscar, Paxil, Prozac, Aminoglycosides, and Lithium are contraindicated because of high teratogenic or fetal risks.