5 main causes of a first trimester miscarriage

#1 Genetic abnormalities

More than half of all first trimester miscarriages are the result of the baby having abnormal chromosomes. If your body detects that the foetus has damaged or missing chromosomes, it will end the pregnancy. In rare cases, one or both of the parents may themselves have a genetic defect, which would impact on the foetus they produce (for example, Robertsonian translocation, or ROB).

#2 Autoimmune disorder

Growing a baby inside the uterus requires adaptations much like any other organ transplantation. Sometimes this “tolerance” is absent, and the embryo or the developing foetus may be “rejected”. Much of this is still not clearly known, but experience has shown that certain factors can be tested and if they’re found to be “rejecting” a foetus, they can be altered to promote tolerance; this, in turn, can reverse or prevent the rejection process, leading to successful live births.

#3 Placental problems

The placenta is an organ that grows in the womb during pregnancy, and if the foetus and placenta are not compatible, the pregnancy may be lost. Likewise, uterine defects, including an abnormal shape, tumours like fibroids and adenomyosis, and adhesions in the uterine cavity, may also cause the sudden ending of a pregnancy.

#4 Hormonal imbalance

Imbalance of certain hormones, for example progesterone, prolactin or thyroid hormone, can result in miscarriage. Progesterone is especially important because it helps to maintain the endometrium lining; if there are low levels of progesterone, the lining may not be ready to support the pregnancy.

#5 Ectopic pregnancy

This potentially serious but rare type of pregnancy occurs when the foetus begins developing outside the womb. Ectopic pregnancies cannot be saved and are a medical emergency requiring immediate treatment.