Dr Bronwyn Moore (gynaecologist) answers:
Early pregnancy losses are very common and commonest causes are failed implantation, blighted ovum (or an embryonic pregnancy) and chromosomal abnormalities. Pregnancy tests have become so sensitive that a pregnancy test will be positive even before the first missed period, as was the case here. A pregnancy test can be positive before any pregnancy is visible. This is a chemical pregnancy - later the pregnancy can be seen on sonar and this is then a clinical pregnancy.
Often times the foetus doesn't implant into the uterus as it should and passes through, the result is a delayed period that is often heavier than normal. If a pregnancy is lost before 8 weeks, the miscarriage is usually complete and no D & C is usually required. Please be reassured that future pregnancies are likely to be uneventful.