Is vitamin K safe during pregnancy?

What does the evidence say about vitamin K during pregnancy?

1. The adequate intake for vitamin K in pregnancy is 75 mcg a day for pregnant people ages 14 to 18 and 90 mcg a day for ages 19 and up, and most people get enough from a normal diet. 1
2. No side effects have been reported in the general population from vitamin K intake above the adequate intake level, though pregnant people should still discuss any supplement with their healthcare provider before starting it. 1
3. Newborns are nearly all physiologically low in vitamin K at birth because the vitamin doesn't cross the placenta efficiently, breast milk contains relatively low amounts, and a newborn's gut hasn't yet developed the bacteria that help produce vitamin K, which is why a vitamin K shot (1 mg, given within 6 hours of birth for a term infant) is standard newborn care. 2
4. A meta-analysis of antenatal vitamin K supplementation found it raised cord-blood and breast-milk vitamin K levels but wasn't shown to significantly reduce neonatal bleeding overall, and noted that vitamin K deficiency can worsen with certain medications like heparin or carbamazepine. 3
5. One study found nearly 39% of pregnant women had low vitamin K2 levels in late pregnancy, and since a newborn's vitamin K2 level tracks closely with the mother's, researchers pointed to maternal vitamin K2 status as relevant to a baby's early bone development. 4

Is vitamin K safe in each trimester?

• First trimester. Vitamin K needs don't change specifically for the first trimester; the adequate intake stays the same across pregnancy. Most prenatal vitamins include some vitamin K, though not always a large amount, so a normal varied diet is what actually covers most of the requirement.
• Second trimester. Green leafy vegetables, vegetable oils, and some fortified foods are the main dietary sources of vitamin K, and continuing to eat these regularly through the second trimester is generally enough to meet the 90 mcg a day target.
• Third trimester. Vitamin K needs stay level into the third trimester, but this is a good time to know that your newborn will get their own vitamin K dose, a shot of 1 mg for a term baby, shortly after birth, separate from anything you take, because babies are born with very low vitamin K stores of their own.

Vitamin K reference amounts