Answer: It can be frightening if you start bleeding during pregnancy - Bleeding during pregnancy, especially during the first trimester, is more common than you might think. - Any passage of blood from the vagina before 24 weeks of pregnancy is termed a threatened miscarriage or threatened abortion. After 24 weeks it’s termed as an ante-partum haemorrhage. You especially need to see a doctor or midwife within 72 hours of any bleeding if you have a rhesus negative blood group (e.g. O-, A-). The reason for this is to check whether there has been a possible mixing of your baby’s blood with yours. If the blood has been mixed, it may cause your body to produce antibodies against positive blood. A positive blood group is more dominant than a negative blood group. It’s most likely your baby will inherit a positive blood group, although you won’t know this before the birth. The blood mixing doesn’t have any bearing on your first pregnancy. But for subsequent pregnancies, if you have another baby with positive blood, your antibodies would attack what it thinks is foreign matter. - Some women experience what is known as ‘breakthrough bleeding’, during the times when a period would have normally been due. Therefore bleeding would appear at around 4, 8 and 12 weeks of pregnancy. It’s often accompanied by the feeling you would normally associate with your period being imminent, i.e. backache, cramps, a heavy sensation in the pelvis, feeling bloated and ‘off’. Painless vaginal bleeding can result from an abnormally placed placenta. Sometimes the placenta implants itself very low down on the uterine wall, and occasionally right over the cervix. This is called placenta praevia and it occurs in about 0.5% of pregnancies.