EDITOR—I have serious doubts about the validity of the data reported by Blanch et al on embryonic abnormalities at medical termination of pregnancy.1 In my experience, embryos are delicate and can be readily disrupted even during careful handling. Although the authors state that “strict criteria were used to distinguish structural abnormalities from traumatic damage,” they give no details of these criteria and whether they have been generally accepted as distinguishing between trauma and abnormality in delicate embryonic tissue. I believe that it is important to specify in how many cases traumatic damage was seen.

Although Blanch et al state that macroscopically abnormal embryos were further examined histologically, they do not report the histological findings and I was surprised that a pathologist was not included as an author. Were all the neural tube and abdominal wall defects confirmed histologically? It is easy to envisage how compression of a delicate embryo during delivery might induce rupture of both the abdomen and central nervous system.

An anembryonic pregnancy rate of 23% (48 in 206 cases) before 9 weeks of pregnancy is high in comparison with the rate of 16% found in a study of 38 abnormal early pregnancies2 and that of 1% in an ultrasound study of 17 820 normal pregnancies (albeit 10-13 weeks' gestation).3 Such a discrepancy must be explained.

I believe that the unexpected finding of a 34% non-viable pregnancy rate can be explained by misinterpretation of macroscopic appearances.

EDITOR—Most (80%) of the embryos that we examined were delivered within intact gestation sacs, protected from trauma by the amniotic fluid and membranes, and without any sign of tissue disruption macroscopically, microscopically, or histologically. In the 20% of pregnancies in which the gestation sac had ruptured during abortion we used strict histological criteria to distinguish structural abnormalities from traumatic damage. Three investigators studied each embryo independently before a classification was determined; when a neural tube defect was suspected on macroscopic inspection, the periderm (future dermis) was examined meticulously and the embryo was classed as having a neural tube defect only if the skin surface was continuous with the developing neural tissue; abdominal wall defects were diagnosed only if there were loops of bowel outside the abdominal wall before Carnegie stage 16 or if other intra-abdominal organs such as the liver were outside the abdominal wall and if the edge of the periderm was histologically rounded rather than ragged.

Anembryonic pregnancy was diagnosed only when the gestation sac was intact. We found an incidence of 33 out of 206 (16%). This is identical with the rate of anembryonic pregnancy quoted by Alcazar et al.1 In our study, the pregnancies were 6-9 weeks' gestation. The discrepancy between the anembryonic pregnancy rate in our study and that in the study by Pandya et al (1%)2 can be explained by the fact that most anembryonic pregnancies would have ended in miscarriage by 10-13 weeks' gestation in the other study.

We are confident that our methods did not overestimate the incidence of pregnancy abnormality.