Double the number, double the trouble? Dr Howard Lee discusses twin pregnancies

Twin pregnancy is a mixed blessing – on the one hand there’s the exciting prospect of an instant family, on the other hand there’s the worrying prospect of more problems during the nine months leading up to the birth and delivery.

Obviously, carrying and delivering two babies at once is more of a feat than just producing one, but the fact remains that pregnancy and birth are physiological states, not symptoms of a disease process. Statistically, it is true that there’s an increased likelihood of problems with twins. However, not all complications of single pregnancies occur more frequently in a twin pregnancy, so don’t worry.

How twin pregnancies happen

• Identical twins. One egg splits after fertilisation into two separate cells – each one of these growing into a baby (usually sharing the same placenta). Having developed from the same cell, they are always the same sex and look alike.
• Non-identical or fraternal twins. Two eggs are fertilised by two different sperm at the same time, (each baby having its own placenta). They can be different sexes and probably will not look any more alike than any brother or sister.

Twin pregnancies are passed down through the female and are more likely to occur if there are already non-identical twins in the family. The prevalence in the UK is about one in 95 deliveries – and this has been increasing over the past couple of decades. Multiple pregnancies also increase as women get older.

Diagnosis

Twin pregnancy used to be diagnosed clinically when the mother reported that her symptoms of pregnancy were worse than usual and the womb was found to be bigger than expected for the gestational dates. Sometimes twins were diagnosed for the first time in labour – certainly a surprise for both the expectant couple and the obstetrician alike. Nowadays, the ultrasound scan performed routinely between the 16th and 20th week usually allows a much earlier diagnosis.

Common concerns and problems with twin pregnancies

Congenital abnormalities. These are conditions recognised at birth, or believed to have been present since birth – and there is an increased risk of this with a twin pregnancy. For this reason, a very thorough ultrasound examination of each foetus will be performed between 20–24 weeks of gestation. If the ultrasound session seems particularly long and ‘intense’ you’ll know why. If an abnormality is suspected following this ultrasound examination, a further investigation will be required. This may mean an amniocentesis.

Nausea. Early in the pregnancy, you may have more nausea because of the higher concentration of hormone being produced from the placenta.

Veins and other troubles. The increased size of the womb leads to greater pressure on the veins in the legs. This will increase the chances of developing a group of conditions which the obstetrician, but not the mum, calls ‘minor problems’. For example, varicose veins in the legs, haemorrhoids (piles) and sometimes swellings of the veins within the vaginal entrance (vulval varices) and these can certainly be uncomfortable and irritable.

Blood pressure. Multiple pregnancies do lead to more problems with high blood pressure and associated problems like eclampsia. So expect your antenatal screenings to be extra thorough. For more information see Reducing the risk of pre-eclampsia.

Rest. It was not uncommon, in my early general practitioner days, for obstetricians to advocate a period of bed rest during the antenatal period and sometimes mums expecting twins were admitted to hospital at 32 weeks to make sure they took things easy. Certainly, we still encourage a regular, daily rest period – and lying comfortably in bed is the best way to relax. So, nothing changes.

Hydramnios. This is an abnormally large amount of fluid surrounding the baby. It also occurs more commonly in twin pregnancies from about week 20. It can increase all those ‘minor problems’ associated with the enlarged womb and adds to any breathlessness you may experience as your pregnancy progresses.

Anaemia. Again, with twins you have a higher risk of anaemia. This can be due to the greater expansion in blood volume that occurs in twin pregnancy. Folic acid requirements are also greater because of the risk of anaemia.

Growth retardation. This can sometimes occur within the womb and often the twins differ considerably in size from each other. Surprisingly, the difference can be greatest amongst identical twins.

Premature birth. There is an increased risk and this means also that the birth weight of twins can be low.

• The average gestation time for singleton pregnancies is just over 40 weeks. For twins it is only 37 weeks.
• Labour starts early in 20–50% of twin pregnancies compared with 5–10% in singleton pregnancies.

Antenatal care will certainly entail more ultrasound screening, tests and investigations and more appointment sessions. It should also include social support and advice, to plan for the extra load before, during and after delivery.

Despite all the reassuring advice, you will undoubtedly develop some anxieties, and it is important that you express them. (You can email me at iVillage with any questions you have.) It doesn’t matter how small or insignificant your concerns – give voice to them because busy medical staff sometimes forget to reassure you about the normality of most births.