Drugs in Pregnancy - NEET PG Obstetrics

When it comes to preparing obstetrics for the NEET PG exam, drugs in pregnancy are one of the most important and high-yielding topics. Through this blog, we have tried to cover all the vital details about the topic so that you recall and revise it quickly.

Make your NEET PG exam preparations of obstetrics simpler and more productive through our medical notes blogs. Keep reading.

FDA CATEGORIES - 5 CATEGORIES

FDA has classified the different drugs used in pregnancy into five letter risk categories. Each category represents the potential of that category drug to cause risk during pregnancy. 

Category A 

• Safe in pregnancy
  • Thyroxine 
  • Multi Vitamins 
  • Folic Acid 

Category B 

• Have adverse effects in animals 
• All studies in human are safe
  • Penicillin 
  • Cephalosporins 
  • Didanosine 
  • Metronidazole 
  • Nitrofurantoin 

Category C

• Teratogenic in animals 
• Inadequate human studies, safe in the few studies done 
• Most commonly used drugs in Obstetrics
  • Mebendazole 
  • Albendazole 
  • Acyclovir 
  • Chloroquine 
  • Lamotrigine (Category C Anti-Epileptic drug: DOC for Epilepsy in pregnancy) 

Category D

• Known human teratogens 
• Given when Benefits > Risk
  • Antiepileptics (Phenytoin, Carbamazepine) 
  • Quinine 

Category X 

• Known Teratogens 
• Totally contraindicated (Risk > Benefits)
  • Alcohol 
  • Androgens 
  • Vitamin A 
  • Lithium 
  • Warfarin (in early pregnancy) 
  • Radio Iodine 
  • Cancer Chemotherapeutic Drugs 
  • Tetracyclines 

ALCOHOL IN PREGNANCY 

Alcohol intake during pregnancy can cause the baby to develop serious conditions and increase the risk of miscarriage. Let’s learn about the risks of alcohol in pregnancy.

Alcohol Related Birth Defects 

• Cardiac: ASD or VSD
• Skeletal: Radio ulnar synostosis, joint contractures 
• Renal: Aplastic or hypoplastic kidneys 
• Eyes: Strabismus, Ptosis, Optic nerve hypoplasia 
• Ear: Conductive or Neuro-sensory hearing loss 
• Minor: Hypoplastic nails, Clinodactyly, Pectus carinatum or excavatum, Camptodactyly, Hockey stick Palmar crease, RailRoad Track Ears) 

Fetal Alcohol Syndrome 

• All are required for diagnosis
  • Dysmorphic Facial features (all 3 required)
    • Small palpebral fissures 
    • Thin vermilion border 
    • Smooth Philtrum 
  • Prenatal and / or postnatal growth impairment 
  • CNS abnormalities (1 required)
    • Structural: Head size < 10^th percentile, significant brain abnormality on imaging 
    • Global cognitive or intellectual deficits 

WARFARIN EMBRYOPATHY

• Warfarin is a Vitamin K antagonist & a potent anticoagulant 
• Low molecular weight: Readily cross placenta 
• Causes Embryotoxic & Fetotoxic effects 
• 6-9 weeks exposure: Warfarin Embryopathy 
• Features
  • Stippling of vertebrae & femoral epiphysis 
  • Nasal hypoplasia 
  • Depression of Nasal bridge 

LEFLUNOMIDE 

• A Pyrimidine synthesis inhibitor 
• Used for Rx of Rheumatoid arthritis 
• C/I in pregnancy because it is a/w multiple abnormalities like
  • Hydrocephalus 
  • Eye abnormalities 
  • Skeletal abnormalities 
  • Embryo death 
• Detectable in plasma for upto 2 years following it’s discontinuation 
• Cholestyramine Treatment/Washout
  • Cholestyramine binds with Leflunomide & helps in early excretion of drug 
  • Cholestyramine Rx is F/b verification of serum levels of Leflunomide (Serium levels of Leflunomide should be undetectable on 2 tests performed 14 days apart) 

FETAL HYDANTOIN SYNDROME 

• D/t intake of Antiepileptics like Phenytoin, Carbamazepine 
• Facial features include
  • Upturned nose 
  • Mild mid facial hypoplasia 
  • Long upper lip with thin Vermilion border 
  • Distal digital hypoplasia 

Important Information 

• At least 3 months washout period for phenytoin is required before planning Pregnancy. If woman presents with pregnancy and is already on phenytoin → do not discontinue 

Related Previous Year Questions

Q. A pregnant woman was given indomethacin for treatment of pain. Which of the following can be a likely outcome in the baby? (NEET 2021)

A. Patent ductus arteriosus 

B. Premature Closure of ductus arteriosus 

C. Patent ductus venosus 

D. Premature closure of ductus venosus 

Answer: Premature Closure of ductus arteriosus 

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