By the 12th week of pregnancy, there is a good chance your doctor will have become aware of the fact you are carrying twins instead of a singleton. According to the Women's Healthcare Topics website, at 12 weeks you are likely to be experiencing an enlarged uterus, greater than normal weight gain and unusually bad morning sickness. By 12 weeks, the doctor may also have been able to detect two heartbeats.
According to the Baby Center website, by 12 weeks the twins should be approximately 3 inches long. Their limbs and organs will be completely formed, although not completely developed or functional. Their faces will look normal. The twins will start to move around, but you won't be able to feel it yet. The baby center also reports that the babies will have reflexes. So as they move around and bump into each other, they will clench their fists and curl their toes.
Changes for the Mother
By the time you are 12 weeks pregnant with twins, you may be experiencing anemia, which the I-am-pregnant website states is normal during pregnancy. However, it is especially common in women carrying twins. Other common changes or symptoms by week 12 of a twin pregnancy include: bleeding gums, constipation, breathlessness, fatigue and changes in libido. Although most of these can happen during any pregnancy, they are more frequent during twin pregnancies. This is because the body takes away from its own blood supply and nutrients to develop the babies, depleting what the mother needs for good health.
Risks and Considerations
There is an increased risk of miscarriage when carrying twins. More specifically, it is possible to miscarry one baby, but still carry the second baby to term. However, the risk of miscarriage decreases considerably at 12 weeks. According to the Women's Healthcare Topics website, when one twin is miscarried before 12 weeks, the loss is "reabsorbed" and in most cases nothing needs to be done. It is possible to lose one baby and never be aware of the fact you started with twins.
Due to the increased risk of miscarriage, as well as the increased risk of preterm labor, Women's Healthcare Topics recommends women carrying twins take special care to stay hydrated and consume nutrient-dense food.