Surveillance And Monitoring Of Twin Pregnancies

The introduction of ultrasound into obstetric practice has helped twin-carrying mothers identify multiple pregnancies antenatally, opening the possibility of screening these pregnancies for both the same pathologies as those screened in single pregnancies and for the management and identification of complications in twin pregnancies.

What is the surveillance and monitoring process in twin pregnancies?

Invasive testing in twin pregnancies is linked with a higher risk than in a single pregnancy. It might be tough to separate the effect of invasive testing from the higher rate of miscarriage in twin pregnancies in the observational data. The loss of pregnancy is 3–4 per cent, and the excess risk of miscarriage linked with second-trimester amniocentesis in twins is 1 per cent.

Procedure in Surveillance and Monitoring of Twin Pregnancy

First-trimester scan in twin pregnancies

Due to the high risk of preterm delivery in twins, accurate first-trimester dating is vital to managing pregnancy. After determining and dating the diagnosis in a twin pregnancy, the most important thing is to know the precise number of chronicities (the placentae number) and foetuses of the pregnancy.


Dating the pregnancy using the CRL before 14 weeks gestation is the standard practice in twins. With natural variation, twin foetuses may rarely be identical in size at the earliest of gestations. The risk of using the smaller CRL to date the pregnancy lies in the assumption that the larger twin is larger for dates and failing to diagnose a growth-restricted smaller twin.


The symptoms available to consider chorionicity differ by gestation, and the diagnosis is more accurate earlier in twin pregnancy. Before ten weeks of gestation, there is the presence of two gestational sacs: the yolk and amniotic, which identify a DCDA pregnancy. After ten weeks, the placental number of masses will be identified.

Twin labelling

After that, labelling of the twins is done at the first scan and must be consistent at subsequent scans. For example, twin one is female on the left and has an anterior placenta, and twin two is male on the maternal right and has a posterior placenta. To reduce confusion, it is better to represent the twins' relative positions in the maternal notes.

What to expect during surveillance and monitoring of twin pregnancies?

The management of foetal structural anomalies is complex in twin pregnancies where the affected foetus shares the intrauterine environment with a sibling that might be present or unaffected by different disorders. The management can be done based on the prognosis for the chronicity and affected twin of the pregnancy. Twins might be identical in size, but the growth discrepancies are linked with poor perinatal results continuously and might be more crucial to the perinatal outcome than the absolute size of individual babies.

The next process involved in the surveillance and monitoring of twin pregnancies is the TRAP sequence. There is a spontaneous demise of the acardiac twin in several cases, so the TRAP sequence is diagnosed as a single foetal demise in the early first trimester.

Optimal TRAP pregnancy management will be achieved using laser photocoagulation of the umbilical blood vessels in the acardiac twin. Expectant management is linked with mortality in the pump twin, while survival after laser therapy is 80 per cent. Pregnancy outcomes are better managed with foetal intervention at early gestations, so early diagnosis is vital, and healthcare professionals must scan twins in the first trimester, which must be maintained to know the condition.

Conjoined twins are the rarest complication seen in a monochorionic pregnancy. It is a condition that results from the late splitting of the blastocyst and occurs in about one per cent of monochorionic twin pregnancies. Advancement in ultrasound helps identify these conjoined twins in the first trimester when several parents can choose for pregnancy termination given the high risk of mortality and morbidity in an ongoing pregnancy.


Ultrasound is a crucial tool at an early stage of monitoring and surveillance of pregnancy. It helps to identify further tests for the prediction of preterm delivery in twins and make prediction models for screening for pre-eclampsia. The cornerstone of the management of twin pregnancies is monitoring and surveillance for potential complications for the foreseeable future.

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1. How are twin pregnancies monitored?

Women with twin pregnancies should have an ultrasound between 11 to 14 weeks. It is necessary to attend this appointment. It is the best time to know what kind of membranes and placenta your twins have, and you can check dates too.

2. How do you monitor twin-to-twin transfusion syndrome?

It develops in pregnant women between 16 to 26 weeks. But, an ultrasound done early, at 10 to 14 weeks, can help doctors determine if there is a twin pregnancy and whether they are sharing a placenta. TTTS is diagnosed by checking the amniotic fluid levels.

3. Is twin pregnancy more complicated?

Yes, a twin pregnancy is a little more complicated than a single pregnancy. Thus, surveillance and monitoring become more important.

4. How can I tell if I have TTTS?

A prenatal ultrasound may reveal signs of TTTS such as unequal amniotic fluid levels, different-sized babies, or evidence of cardiac malfunction in one or both babies. Early diagnosis is important for the best outcomes.

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