Women who are known to be pregnant should not take COCPs. Postpartum women who are breastfeeding are also advised not to start COCPs until 4 weeks after birth due to increased risk of blood clots. While studies have demonstrated conflicting results about the effects of COCPs on lactation duration and milk volume, there exist concerns about the transient risk of COCPs on breast milk production when breastfeeding is being established early postpartum. Due to the stated risks and additional concerns on lactation, women who are breastfeeding are not advised to start COCPs until at least six weeks postpartum, while women who are not breastfeeding and have no other risks factors for blood clots may start COCPs after 21 days postpartum. Severe hypercholesterolemia and hypertriglyceridemia are also currently contraindications, but the evidence showing that COCP's lead to worse outcomes in this population is weak. Obesity is not considered to be a contraindication to taking COCPs.