Doctors aren't able to pinpoint the reason for most early miscarriages, but it seems that babies who are abnormal in some way tend to miscarry. At least half of all miscarriages in the first trimester of pregnancy are the result of chromosomal abnormalities that prevent the baby from developing normally. Maternal infections, uncontrolled diabetes, thyroid problems, uterine abnormalities, or the presence of certain antibodies during pregnancy can also cause an early miscarriage. The most obvious signs are period-like pains and heavy bleeding which may include blood clots. However, you can miscarry without even knowing, especially early in pregnancy.
Many women mistake a miscarriage for a late period.
Some miscarriages are discovered only during a routine antenatal visit, when the doctor or midwife cannot find the baby's heartbeat. Wendy didn't know she'd miscarried the first time until she saw her midwife for an antenatal appointment at 12 weeks. This confirmed her worst fears. The ultrasound scan revealed that Wendy had suffered a missed abortion. Her baby had died but was still inside her.