Beginning in the first trimester, mean platelet counts decreased during pregnancy in all women in a recent evaluation of women who delivered at Oklahoma University Medical Center between 2011 and 2014. The platelet counts were compared with those of nonpregnant women who were included in the National Health and Nutrition Examination Survey from 1999 through 2012. Researchers found:
- Among the 15,723 deliveries that occurred during the study period, 7,351 women had sufficient data for the analyses.
- Of these women, 4,568 had uncomplicated pregnancies, 2,586 had pregnancy-related complications, and 197 had preexisting disorders associated with gestational thrombocytopenia.
- Among the women who had uncomplicated pregnancies, the mean platelet count in the first trimester was 251,000 per cubic millimeter, which was lower than the mean platelet count in the 8,885 nonpregnant women.
- Platelet counts of <150,000 per cubic millimeter at the time of delivery were more common among women with pregnancy-related complications than among women who had uncomplicated pregnancies.
- In women with a platelet count of <100,000 per cubic millimeter, a cause other than pregnancy or its complications should be considered.
Reese JA, Peck JD, Deschamps DR, et al. Platelet counts during pregnancy. N Engl J Med. 2018;379:32-43. doi:10.1056/NEJMoa1802897.