Denmark: A new study supports the recommendation of low-molecular-weight heparin (LMWH) during pregnancy in women with prior venous thromboembolism (VTE) as the fetal risk was found to be lowest in unexposed and LMWH-exposed pregnancies. The safety of non-VKA oral anticoagulant (NOAC) during pregnancy was not clear owing to the rarity of NOAC exposure.
Mette Sogaard, Department of Cardiology, Aalborg University Hospital, Denmark, and colleagues aimed to determine first-trimester anticoagulant exposure and risks of adverse pregnancy-related and fetal outcomes in their study published in The American Journal of Medicine.

For this purpose, the researchers identified all pregnant women with preconception VTE using Danish nationwide registries and lined data on exposure to vitamin K antagonist (VKA), low-molecular-weight heparin, or non-VKA oral anticoagulant during pregnancy. Pregnancy-related and fetal outcomes associated with first-trimester anticoagulant exposure were then assessed.
The findings of the study were as follows:
· Among 4490 pregnancies in women with preconception venous thromboembolism (mean age 31 years, 40% nulliparous) during the first trimester, 63.1% were unexposed, and 25.9% were exposed to LMWH, 10.4% VKA, and 0.6% NOAC.
· Adverse outcomes were lowest in unexposed and LMWH exposed.
· Compared with unexposed, VKA was associated with higher risks of preterm (adjusted odds ratio [OR] 2.26) and very preterm birth (adjusted OR 3.78), shorter mean gestational age was associated with VKA (−7.5 days) or NOAC (−2.3 days), and lower mean birthweight with VKA (−55 g) or NOAC (−190 g).

· Adjusted ORs for small-for-gestational-age infants were 1.07 with VKA, and 3.29 with NOAC.
· Mean 5-minute Apgar score (9.8) and congenital defect prevalence (8.4%-10%) varied little across exposure groups.
To conclude, "fetal risk was lowest in unexposed and LMWH-exposed pregnancies, supporting the recommendation of LMWH during pregnancy. The safety of NOAC during pregnancy is not clear due to the rarity of NOAC exposure."
Reference:
Søgaard M, Skjøth F, Nielsen PB, Beyer-Westendorf J, Larsen TB. First Trimester Anticoagulant Exposure and Adverse Pregnancy Outcomes in Women with Preconception Venous Thromboembolism: A Nationwide Cohort Study. Am J Med. 2022 Apr;135(4):493-502.e5. doi: 10.1016/j.amjmed.2021.10.023. Epub 2021 Nov 17. PMID: 34798098.