Question

Which one of the following statements is NOT correct?

• A. Unfractionated Heparin does not cross the placenta.
• B. Low molecular weight Heparins can cross the placenta.
• C. Warfarin crosses the placenta.
• D. Breast feeding is safe for the infant of a mother taking Warfarin.

Hint:

Both forms of heparin are too large and charged to cross the placenta, only warfarin does.

Answer 1

The Correct Option is B

The question tests which fact about heparin, warfarin, and the placenta is false. The rule to remember is that big charged drug molecules stay out of the fetal side, while small ones pass through freely.

1. Unfractionated Heparin does not cross the placenta: True. Its large size and strong negative charge block it from crossing, which is why it is a first choice anticoagulant during pregnancy.
2. Low molecular weight Heparins can cross the placenta: False. Even though these are shorter chains than unfractionated heparin, they remain large charged molecules and do not cross the placenta in practice.
3. Warfarin crosses the placenta: True. It is small and fat soluble, so it passes freely into the fetal circulation and can harm the developing fetus, especially in the first trimester.
4. Breast feeding is safe for the infant of a mother taking Warfarin: True. Warfarin sticks tightly to proteins in the mother's plasma, so very little reaches the breast milk, making breastfeeding safe.

Since three of the statements are medically accurate and only the claim about low molecular weight heparin crossing the placenta is wrong, that is the incorrect statement asked for.

Let's summarize:

• Both unfractionated and low molecular weight heparin are placenta safe.
• Warfarin crosses the placenta but is still safe during breastfeeding.

So the statement that is not correct is that low molecular weight heparins can cross the placenta.