Madam, - Colette Browne (April 3rd) seems to have a rather simplistic view of the mode of action of the contraceptive pill. As well as preventing ovulation, it can effect changes in cervical mucus which block the passage of sperm; but it can also effect changes in the endometrium which prevent an embryo from implanting.
The progesterone-only pill has a weak effect on ovulation but has a very powerful one on cervical mucus. And no, cervical mucus was not invented by a Catholic, Dr John Billings. The world expert on cervical mucus is Prof Eric Odeblad, a good Lutheran at Umeå University in Sweden. If the first two effects do not prevent the meeting of ovum and sperm, the pill may prevent the embryo from implanting.
Of course, if one believes that human life begins only after implantation, as Baroness Warnock does, one will not accept that the pill is ever abortifacient. But the Catholic Church is not alone in holding that human life begins at fertilisation.
As regards the Mirena device, which was given honourable mention in HEALTHpluson April 1st, there is no evidence to show that it acts in any way other than by causing an early abortion. The fact that there are up to 100,000 women here in Ireland using it, mostly as family planning, is alarming. Where there is genuinely very heavy menstrual bleeding, the use of the Mirena can be justified: it is effective in reducing this bleeding. It would be a counsel of perfection to ask a woman to practice natural family planning while using it for this purpose. But it is the only ethical alternative to the possibility of having frequent early abortions.
Theresa Judge's report that, due to Mirena, the number of hysterectomies has fallen dramatically is somewhat premature. In an American study, it was found that 42 per cent of women treated with Mirena for heavy bleeding needed hysterectomy at the end of five years. - Yours, etc,
Dr HELEN T.O'BRIEN, Rosemount, Booterstown, Co Dublin.