And only a fifth of the 436 men turned up for both of the tests needed to finally put them in the clear, according to a study carried out by researchers at the Cleveland Clinic Glickman Urological Institute in Ohio, USA.
Of the 75 per cent that did attend their first, eight-week test, a quarter provided samples that still contained sperm. 80 of the 83 men were producing nonmotile (present but inactive) sperm, but three were producing motile (present and active) sperm, including one who was eventually diagnosed with a vasectomy failure.
65 of the 80 men producing nonmotile sperm were clear at their 12-week checks, but six months after their procedure eight men were still producing positive sperm samples. By ten months, all but the vasectomy failure were finally in the clear.
"Our results show that only three-quarters of the men in the study turned up for their eight-week sperm test, which means that a quarter of them had no idea whether the procedure had worked and whether their partner could still fall pregnant" says lead author Dr Nivedita Dhar, Chief Resident in Urology at the Clinic.
"It is impossible to assess the true vasectomy failure rate in the full study sample as many failed to turn up for follow-up tests, despite careful counselling.
"But what concerns us most is that a quarter of the men who had vasectomies did not return for any tests, despite us stressing the important of these follow-ups" adds Dr Dhar.
According to the researchers up to 90 per cent of urologists require two semen samples to confirm sterility and up to 95 per cent request further samples if nonmotile sperm are present. Doctors recommend that couples use additional contraception u
Contact: Annette Whibley
Blackwell Publishing Ltd.