Vitamin K is a fat-soluble vitamin group that includes phylloquinone (K1) and a series of menaquinones (K2), which are compounds with a similar chemical structure. The body needs vitamin K for various physiological functions, including blood clotting and bone metabolism. It is naturally present in some foods and available as a dietary supplement.
Vitamin K’s Role in Pregnancy
Vitamin K helps maintain normal blood clotting for expectant mothers, reducing the risk of maternal bleeding during labor and postpartum recovery. It helps the body produce proteins necessary for blood clot formation. Beyond blood clotting, vitamin K, especially K2, contributes to bone metabolism and regulates blood calcium levels for the mother.
For the developing fetus, adequate vitamin K levels are important for healthy skeletal development. Low levels can pose a risk to both mother and fetus, potentially leading to bleeding complications. However, vitamin K transfer from the mother to the fetus through the placenta is limited, meaning the fetus may still have low levels even with sufficient maternal intake.
Obtaining Vitamin K
Vitamin K comes in two main natural forms: K1 (phylloquinone) and K2 (menaquinones), each found in different food sources. Vitamin K1 is predominantly found in plant-based foods, such as green leafy vegetables like kale, spinach, broccoli, and Brussels sprouts, as well as plant oils like canola, soybean, and olive oil. Vitamin K2 is present in some animal-based foods and fermented products, including cheese, full-fat dairy, meat (pork, chicken), egg yolk, and natto. Gut bacteria can also produce menaquinones (K2) in the human body.
For adults, the recommended adequate intake for vitamin K is 1 microgram per day per kilogram of body weight, or about 90 micrograms daily for women, including those who are pregnant or lactating. Most individuals can meet their vitamin K needs through a varied and balanced diet. Supplemental vitamin K is not routinely recommended for pregnant women, but it may be advisable in specific circumstances, such as with malabsorption disorders or certain medications that affect vitamin K metabolism. Always consult a healthcare provider before taking any supplements during pregnancy.
Vitamin K for Newborns
Newborn babies are born with naturally low levels of vitamin K, putting them at risk for a bleeding disorder called Vitamin K Deficiency Bleeding (VKDB). This deficiency occurs because vitamin K does not easily cross the placenta from mother to baby during pregnancy. Additionally, a newborn’s intestines do not yet have enough bacteria to produce sufficient vitamin K. Breast milk also contains low levels of vitamin K, which is often not enough to protect a baby from VKDB.
To prevent VKDB, a single vitamin K injection is routinely given to newborns, usually within six hours of birth, into the thigh muscle. This injection increases the baby’s low vitamin K levels and helps their blood clot normally. VKDB can cause severe bleeding, including in the brain, which can lead to brain damage or be fatal. While some European countries offer an oral form of vitamin K, it is less effective than the injection, especially in preventing bleeding in the brain. Maternal vitamin K intake or supplementation during pregnancy does not negate the need for the newborn injection.