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Defects in the "head end" lead to anencephaly, when the bones of the skull don't form properly.At the same time, the heart is forming as a simple tube-like structure.During the third week after the first day of your last period, your fertilised egg moves along the fallopian tube towards the womb.The egg begins as a single cell, which divides again and again.By the time the egg reaches the womb, it has become a mass of more than 100 cells, called an embryo.Once in the womb, the embryo burrows into the lining of the womb. In weeks 4-5 of early pregnancy, the embryo grows and develops within the lining of the womb.If a pregnancy ends before the 24th week of pregnancy, it's called a miscarriage.
Being in hospital allows staff to keep an eye on you and your baby, so they can act quickly if there are further problems.
The egg has to be removed – this can be through an operation or with medicines. To work out what is causing the bleeding, you may need to have a vaginal or pelvic examination, an ultrasound scan or blood tests to check your hormone levels.
Your doctor will also ask you about other symptoms, such as cramp, pain and dizziness. If your symptoms are not severe and your baby is not due for a while, you will be monitored and, in some cases, kept in hospital for observation.
Most miscarriages occur during the first 12 weeks (three months) of pregnancy and, sadly, most cannot be prevented. Ectopic pregnancies (when a fertilised egg implants outside the womb for example, in the fallopian tube) can cause bleeding, but are less common than miscarriages.
It's a dangerous condition, because the fertilised egg can't develop properly outside the womb.