Re: Incidence of pulmonary and venous thromboembolism in pregnancies after in vitro fertilisation: cross sectional study
I did not write, as the authors say, that increases in thrombosis in IVF pregnancies “should” be due to progesterone use but “could” be. My paper, “Venous changes with oral contraceptives”, recorded different venous effects due to over 60 dose combinations of seven types of progestins and two types of oestrogens.1 Combinations with a lower progesterone and higher oestrogen balance immediately produced more dilated endometrial venous sinusoids and/or stromal condensation relating to venous complaints than sequential combinations using oestrogen only pills for 15 days. An increased risk of thrombosis is due to changes in blood vessels, blood flow as well as changes in blood constituents.
One lesson of postpartum stilboestrol-induced thrombosis epidemic in the 1950s and 1960s was that untreated pregnancy per se carried a very low risk of thrombosis.2 The risk will have increased now because many women have taken contraceptive progestins for years before becoming pregnant. Some of them develop the Antiphospholipid Syndrome or Systemic Lupus Erythematous and have a lifetime’s increased risk of thrombosis.3,4
Further hormone use is a mistake.
1.Grant ECG. Venous effects of oral contraceptives. BMJ 1969;2:73-7.
2.Grant ECG. Thrombosis and heart attacks with contraceptive and menopausal hormones. J Nutr Environ Med 1998; 8:159-167.
3.Grant ECG. Systemic lupus erythematosus. Lancet. 2001 Aug 18;358(9281):586.
4.Grant ECG. The Hughes (Anti-phospholipid) Syndrome. J Nutr Environ Med 1998; 8:1 59-167
Competing interests: No competing interests