N elson-Piercy and coworkers (201a1) assessed the safety of tinzaparin through a comprehensive study of 1267 treated pregnant women. There were no maternal deaths or complications from regional analgesia. Although thrombocytopenia developed in 1.8 percent, there were no cases of heparin-induced thrombocytopenia (p. 1015). he allergy incidence was 1.3 percent. Osteoporotic fractures in three women (0.2 percent) were judged to be related to tinzaparin (p. 1015). A total of 43 women (3.4 percent) required medical intervention for bleeding. Of 15 stillbirths, four were judged as possibly being related to tinzaparin use. But, none of the neonatal deaths or congenital abnormalities was attributed to tinzaparin. The authors concluded that tinzaparin during pregnancy was safe for mother and fetus. LMWHs are also safe during breastfeeding (Lim, 2010).
However, LMWHs should be avoided in women with renal failure. Moreover, when given within 2 hours of cesarean delivery, these agents raise the risk of wound hematoma (van Wijk, 2002).
Women receiving either therapeutic or prophylactic anticoagulation should be converted from LMWH to the shorter halflife UFH in the last month of pregnancy or sooner if delivery appears imminent. he purpose of conversion to UFH has less to do with any risk of maternal bleeding at the time of delivery, but rather with neuraxial blockade complicated by an epidural or spinal hematoma (Chap. 25, p. 496). The American College of Chest Physicians recommends that women scheduled for a planned delivery who are receiving twice-daily adjusteddose subcutaneous UFH or fWH discontinue their heparin 24 hours before labor induction or cesarean delivery (Bates, 2012). Patients receiving once-daily LMWH should take only 50 percent of their normal dose on the morning of the day before delivery. he American College of Obstetricians and Gynecologists (2017 c) advises that adjusted-dose subcutaneous LlvfWH or UFH can be discontinued 24 to 36 hours before an induction of labor or scheduled cesarean delivery. he American Society of Regional Anesthesia and Pain Medicine advises withholding neuraxial blockade for 10 to 12 hours after the last prophylactic dose of LMWH or 24 hours after the last therapeutic dose (Horlocker, 2010).
If a woman begins labor while taking UFH, clearance can be veriied by an aPTT. Reversal of heparin with protamine sulfate is rarely required and is not indicated with a prophylactic dose of heparin. For women in whom anticoagulation therapy has temporarily been discontinued, pneumatic compression devices are recommended.
• Anticoagulation with Warfarin Compounds
Vitamin K antagonists are generally contraindicated because they readily cross the placenta and may cause fetal death and malformations from hemorrhages (Chap. 12, p. 247). They do not accumulate in breast milk and are thus safe during breastfeeding.
Postpartum venous thrombosis is usually treated with intravenous heparin and oral warfarin initiated simultaneously. The initial dose of warfarin is usually 5 to 10 mg for the first 2 days. Subsequent doses are titrated to achieve an international normalized ratio (INR) of 2 to 3. To avoid paradoxical thrombosis and skin necrosis from the early anti-protein C efect of warfarin, these women are maintained on therapeutic doses of
UFH or LMWH for 5 days and until the INR is in a therapeu tic range for 2 consecutive days (American College of Obstetri cians and Gynecologists, 2017 c; Stewart, 2010).