Twins plus

What is different about a twin pregnancy?

Many women who have a multiple birth manage well physically and do not have major complications, but this cannot be predicted easily and all twin pregnancies are considered higher risk.

Growing two babies at once comes with increased demands on your body and these are not just in physical size. Exaggerated nausea and vomiting, tiredness, ligamentous and other pains, reflux and, for your babies, a birth around 35-36 weeks as your uterus is full term size early, are all common.

In simple terms, all the things that happen when pregnant with a single baby are about twice as common, occur earlier and are more significant with twins.

How do I know what type of twins I am having?

Most parents-to-be and families are fascinated by twins and are particularly interested in if your babies are identical or non-identical (fraternal).

Broadly speaking in terms of your pregnancy care, however, there are two main groups of twins, those that share a placenta and those that do not.

Identical and fraternal twins

Twins that share a placenta are always identical. They arise from one egg which is fertilised by one sperm and then divides into two babies with (usually) one placenta.

Twins that have separate placentas are usually fraternal but can occasionally be identical twins. This is because identical twins who originate from one fertilised egg which divides, can do this early enough to implant completely separately from each other in the same way that fraternal twins do with individual placentas that do not share blood flow.

Fraternal twins begin as two separate eggs that are fertilised by two separate sperm and are biologically the same as siblings who are born at separate times, they just happen to share a uterus. Because each fertilised egg develops its own placenta and membranes, their placentas are entirely separate. These type of twins are called dichorionic-diamniotic, di-di or DCDA.

How does this affect my care?

When it comes to how your pregnancy is cared for, placental sharing is what determines the frequency of scans, monitoring and risks for your pregnancy.

Sharing a placenta is important as these twins, called monochorionic-diamniotic, mo-di or MCDA, can develop problems related to unequal share of the placenta and unequal blood flow between the babies. These problems are called selective growth restriction, twin-twin transfusion and twin anaemia-polycythaemia.

A small minority of twins that share a placenta also share the amniotic sac and have no barrier between the babies. Apart from being very rare, these twins called monochorionic-monoamniotic, mo-mo or MCMA, can develop problems related to umbilical cord twisting of the two babies.

You will be told the kind of twins you are having most reliably early in your pregnancy, between 6 and 14 weeks when it is much easier to see where the placentas are forming and the early dividing membrane between your babies. This is harder to determine later in the pregnancy as the placenta(s) grow and can appear as one mass.

What complications can occur in my pregnancy?

As outlined above, twins carry an increased chance of pregnancy complications, this can be considered roughly double for any complication that can affect a woman carrying one baby.

Women expecting twins have higher rates of hyperemesis gravidarium (nausea and vomiting with dehydration and loss of weight), iron deficiency anaemia, more severe pelvic and ligamentous pain, as well as increased rates of gestational diabetes and pre-eclampsia and severity of both these conditions.

For your babies, being a twin means a much higher rate of premature birth either because labour occurs early or because there is a complication in the pregnancy that means birth is recommended. This can be very premature (less than 32 weeks) in 10 percent of twins and sometimes around or before 23-24 weeks. It is also much more common to be very small (growth restricted) in the womb.

In twins who share a placenta, additional problems can occur including uneven blood flow between your babies, and where only one baby is affected by a serious abnormality, creating treatment challenges.

A dedicated twins clinic has experience in anticipating and treating these problems and increases your chance of a healthier pregnancy and birth.

What extra care will I need?

Twin pregnancies, in addition to standard routine pregnancy care, are recommended the following additional steps:

• A multivitamin supplement. Discuss the role of low dose aspirin with your caregiver for pre-eclampsia risk reduction.
• A good quality ultrasound scan between 11 and 14 weeks to be certain of the number of babies present, type of twins (sharing a placenta or not) and accurate due date.
• Down syndrome screening is still possible with first trimester combined screening or NIPT testing (Harmony, Generation next, Percept and other) and is encouraged.
• Additional ultrasounds:
  • Starting at 16 weeks ever fortnight for twins that share a placenta
  • Starting at 24 weeks and every month for twins that do not share a placenta
  • You may be recommended more ultrasound scans if complications occur.

Should I do anything differently when pregnant with twins?

Most women with twins benefit from early engagement with multiple birth support groups such as AMBA (Australian Multiple Birth Association), as well as childbirth education classes particularly for first babies. Learn more about the support groups available to families raising multiple babies.

Consider finishing work earlier due to increased physical symptoms and size than with a singleton pregnancy and expect a greater pregnancy weight gain than with a single baby.

Please contact the hospital pregnancy assessment unit if you have symptoms of possible preterm labour including contractions or leaking water.