OB Drugs

-- Preterm Labor < 34 weeks


  • Indication: Prevention of Rh Sensitization in Rh (-) mother
  • Timing:
    • Uterine bleeding or Trauma
    • Routine scheduled dosing for Rh negative mother
      • Gestational age: ~ 28 wks (12 wks before delivery)
        • If delivery does not occur within 12 wks after dose, a second 300 mcg dose is recommended.
        • If the first dose is prior to 26 wks gestation (in case of abdominal trauma, vaginal bleeding etc.) , administer q12wks to ensure adequate levels of passively acquired anti-D.
        • If delivery occurs within 3 weeks after the last antepartum dose, a postpartum dose may be withheld, but testing for fetal-maternal hemorrhage of > 15 cc should be performed.
      • Postpartum
  • Dose:
    • Uterine Bleeding:
      • RhoGAM dose based  on Kleihauer-Betke
      • Give 300 mcg per 30 ml fetal whole blood or 15 ml pRBC
    • No Uterine Bleeding (Termination of pregnancy - Induced or spontaneous):
      • Gestation < 13 wks: RhoGAM 50 mcg IM
      • Gestation > 13 wks: RhoGAM 300 mcg IM


  • Guidelines for nutritional supplementation:
    • An additional 1 00-300 kcal/day; 500 kcal/day during breastfeeding.
    • Folic acid supplements (-1. neural tube defects for all reproductive-age women) : 0.4 mg/day, or 4 mg/day for women with a history of neural tube defects in prior pregnancies.
    • Iron: Starting at the first visit, 30 mg/day of elemental iron (or 150 mg of iron sulfate).
    • Calcium:
      • 1,300 mg qd for < 19 years of age;
      • 1,000 mg qd for > 19 years of age.
  • Additional guidelines for complete vegetarians:
    • Vitamin D: 400 IU/day.
    • Vitamin B12: 2 mcg/day.


  • Stadol 1mg IM x 1  OR q4h prn
  • Nalbuphine IV 10-20 mg q 3-4 h.
  • Fentanyl 25-100 μg IV/IM q 1-2 h.
  • Phenergan Topical 25mg x1

Pain control During Labor & Delivery

Labor pain is caused primarily by distention of mechanoreceptors in the uterus and cervix during stage I and by stretching and/or tearing of the birth canal and pelvic ligaments during stage II. Fetal malpresentation and nulliparity are physiologic risk factors for ↑ pain, but fear or emotional distress can exacerbate pain as well. A feeling of control over the labor process can greatly improve patients’ experience of labor; thus, early education about the labor process and pain control options, along with encouragement of maternal involvement in the decision-making process, is key. Treatment options are as follows:

  • Pharmacologic options: Vary according to stage.
  • Stage I:
    • Nalbuphine IV 10-20 mg q 3-4 h.
    • Stadol 1mg IM x 1  OR q4h prn
    • Fentanyl 25-100 μg IV/IM q 1-2 h.
    • Epidural anesthesia (continuous drip of local anesthetic and opiate, e.g., bupivacaine and fentanyl). Requires bed rest, urinary catheter
      placement, and continuous fetal monitoring.
    • Spinal anesthesia (opioid injection alone during early labor, or combination opioid/local anesthetic later in labor and/or for C-section).
      Requires bed rest, urinary catheter placement, and continuous fetal monitoring.
  • Stage II:
    • Pudendal block (10 mL 1% lidocaine injected posterior to both ischial spines).
    • Local anesthetic into the perineum, especially if an episiotomy is to be performed.
    • Epidural/spinal anesthesia may be initiated during the second stage (see above) but is less desirable given the prolonged latency of medications and the potential for fetal respiratory depression.

Contraindication to spinal/epidural

  • Blood pressure too low (uncorrected hypovolemia)
  • Koagulopathy (bleeding disorder)
  • Pressure (↑ ICP)
  • Anatomic back problems
  • Infection of the soft tissue overlying the epidural injection site
  • No (the patient refuses)

Available Methods of
Anesthesia and Analgesia

  • Uterine contractions and cervical dilation result in visceral pain (T10-L1).
  • Descent of the fetal head and pressure on the vagina and perineum result in somatic pain (pudendal nerve, S2-S4).
  • In the absence of a medical contraindication, maternal request is a sufficient medical indication for pain relief during labor.
  • Absolute contraindications to regional anesthesia (epidural,
    spinal, or combination) include the following :
    • Refractory maternal hypotension
    • Maternal coagulopathy
    • Maternal use of a once-daily dose of low-molecular-weight heparin (LMWH) within 12 hours.
    • Untreated maternal bacteremia
    • Skin infection over the site of needle placement.
    • ↑ ICP caused by a mass lesion
Parenteral (opioid agonists & agonist-antagonists) Produces a limited analgesic effect in labor (primarily acts through sedation);
Increases the risk of neonatal naloxone administration and five-minute Apgar scores < 7 (due to significant transplacental passage of these drugs);
Decreases FHR variability.
Provides an adequate level of pain relief for some women without the risks associated with regional anesthesia.
Epidural - Can result in pruritus, fever, hypotension, and transient FHR deceleration.
- Increase risk of of vacuum- or forceps-assisted delivery
Provides the most effective form of pain relief;
Can also be used for cesarean delivery or postpartum tubal ligation.
Spinal Acts for a limited duration;
Puts patients at risk for hypotension, postdural puncture headache, and transient neurologic symptoms.
Rapid-onset analgesia that provides excellent pain relief for procedures of limited duration (30-250 minutes).
Combined spinal epidural Carries the risks of both procedures;
May increase the risk of bradycardia and emergent cesarean delivery over epidural analgesia alone.
Offers the rapid onset of spinal analgesia combined with the ability to prolong the duration of analgesia with continuous epidural infusion.
General Requires airway control;
Carries a significant risk of maternal aspiration and neonatal depression (inhaled anesthetic agents readily cross the placenta);
Associated with higher maternal morbidity rates than epidural anesthesia.
Used in emergent cesarean delivery and indicated in some cases of FHR abnormality;
Can be useful in cases where regional anesthesia is absolutely contraindicated.
Local (e.g., lidocaine, 2-chloroprocaine) In rare circumstances, can cause seizures, hypotension, and cardiac arrhythmias. Provides anesthesia (20- to 40-minute duration) before episiotomy and during repair of lacerations; can be used to perform a pudendal block.

Source: FA Step 2CK


Antihypertensive Therapy:
Antihypertensive medications should not be administered unless BPs are persistently > 160/110.)
Hydralazine  5-10mg IV q20min (max: 20mg)
Methyldopa 250mg PO bid, max: 4g/day
Labetalol  20mg, 40mg, 80mg IV q10min (220mg)
                100mg PO bid, max: 2400 mg/day
                1 mg/kg infusion (maximum 220 mg)
Nifedipine 10 mg po and repeat in 30 minutes, if necessary; [oral nifedipine lowers BP more quickly than did IV labetaolol. ]
Sodium nitroprusside 0.25 ug/kg/min to a maximum of 5 ug/kg/min


  • Cytotec 50mcg PO, then 25mcg 4 hours later IF no cervical change.
  • Pitocin start @ 2 ml/min, increase by 2 ml/min, q 15 min, (max 20 ml/min)


  • Brethine (terbutaline, β-agonist) 0.25mg SQ q20min x 3 then q3h
  • Procardia (nifedipine) 10-20mg po q4-6h (consider in pt. w/ elevated BP
  • Mg Sulfate 4-6g IV loading dose, then 2g/hr, adjust by 0.5g/hr if needed OR 2 g amp IM x 2
  • Contraindications:
    • > 4cm dilated
    • Chorioamnionitis
    • Abruptio Placenta
    • Non-reassuring FHT


< 34 weeks with contractions
  • Celestone (betamethasone) 12mg IM q24h x 2
  • Decadron (dexamethasone) 6mg IM q12h x 4

NOTE: IF plan to discharge, Discharge pt. ONLY after completion of steroid dose. DO NOT leave the remaining doses to be given as outpt. in clinic.


GBS Proph:
Pen G - 5 million U IV, then 2.5 million U q4h

If allergic - what is allergy?
  • Low Risk (rash w/o urticaria)
    • Cefazolin 2g IV, then 1g q8h x48hr, then Keflex 500mg PO QID x5d
  • High Risk (anaphylaxis)
    • Vancomycin 1g IV q12h

PPROM: ( 7 days )

  • Cover GBS: Ampicillin 2g IV q6h x48 hr, then Amoxicillin 875mg PO bid x5 days.
    Cover Mycoplasma: Azithromycin 1g on admission.
  •  Penicillin Allergy:
    Low Risk (rash w/o urticaria) High Risk (anaphylaxis)
    Cefazolin 2g IV, then 1g q8h x48hr, then Keflex 500mg PO QID x5d
    Azithromycin 1g on admission
    Vancomycin 1g IV q12h
    Clindamycin 900mg IV q8h
    Gentamicin 7mg/kg ideal body weight q24h x 2 doses,
    Clindamycin 300mg PO q8h x5d
    Azithromycin 1g x1


ITE 2013, Q61
A 30-year-old female at 36 weeks gestation has a positive culture for group B Streptococcus. Her past medical history is significant for the development of a nonurticarial rash in response to penicillin.
Which one of the following is most appropriate for intrapartum antibiotic prophylaxis in this patient?
A) Azithromycin (Zithromax)
B) Clindamycin (Cleocin)
C) Vancomycin (Vancocin)
D) Ampicillin
E) Cefazolin

Postpartum Hemorrhage

Loss of > 500 ml of blood following VAGINAL delivery,
1000 ml of blood following CESAREAN section
  • Tone (Uterine Atony)
    • Massage uterus
    • Pitocin 10ml/min
    • Methergine 2mg IM q2h
    • Hemabate (PGF2) 25mg IM q15min
  • Tissue (retained placenta)
    • Inspect
    • Consider conscious sedation
    • Manually examine uterus
  • Trauma
    • Vaginal wall, Cervix
  • Thrombophilia (Bleeding Disorders)
    • vonWillebrand dz Most Common.