At least two of these appointments should be with the specialist obstetrician.
Combine appointments with scans when crown–rump length measures from 45 mm to 84 mm (at approximately 11 weeks, 0 days to 13 weeks, 6 days) and then at estimated gestations of 20, 24, 28, 32 and 36 weeks.
Offer additional appointments without scans at 16 and 34 weeks.
Offer delivery from 37 weeks’ gestation.
At least two of these appointments should be with the specialist obstetrician.
Combine appointments with scans when crown–rump length measures from 45 mm to 84 mm (at approximately 11 weeks, 0 days to 13 weeks, 6 days) and then at estimated gestations of 16, 18, 20, 22, 24, 28, 32 and 34 weeks.
Offer delivery from 36 weeks’ gestation.
At least two of these appointments should be with the specialist obstetrician.
Combine appointments with scans when crown–rump length measures from 45 mm to 84 mm (at approximately 11 weeks, 0 days to 13 weeks, 6 days) and then at estimated gestations of 20, 24, 28, 32 and 34 weeks (see 55).
Offer an additional appointment without a scan at 16 weeks.
Offer delivery from 35 weeks’ gestation.
At least two of these appointments should be with the specialist obstetrician.
Combine appointments with scans when crown–rump length measures from 45 mm to 84 mm (at approximately 11 weeks, 0 days to 13 weeks, 6 days) and then at estimated gestations of 16, 18, 20, 22, 24, 26, 28, 30, 32 and 34 weeks.
Offer delivery from 35 weeks’ gestation.
For higher order multiple pregnancy, it is advised that antenatal care should be delivered by fetal medicine specialists and should involve regular serial ultrasound but there is no published literature to guide this care and it would need to be individualized.
Information and emotional support
The risks of multiple pregnancy and the additional elements of antenatal care required to mitigate and identify them can lead to a certain level of anxiety for the woman and her partner/family. In today’s world, women also have access to a wide range of information from various sources (internet, media, etc.) some of which may be poor or misleading. It is important to ensure women are given good information, are guided to reputable sources of further information, and have the opportunity to clarify matters that are unclear to them. They should be encouraged to explore socioeconomic issues related to caring for and supporting more than one child. This process of information giving is ongoing and can be delivered in a number of formats.
Nutritional supplements, diet and lifestyle advice
In multiple pregnancy, as the metabolic rate of the mother is greater than in singleton pregnancy, it has been suggested that a high-calorie diet may help maintain her nutritional state. The counterargument is that boosting weight gain might not be advantageous. There are no RCTs to advise whether specific dietary advice for women with multiple pregnancy does more good than harm.
The NICE guideline group reviewed the limited literature on nutritional supplements and dietary advice in multiple pregnancy and concluded that the few published studies were of very low quality and there was no evidence to give different advice to that given in singleton pregnancy[4]. However, they emphasized it is important to be aware of the higher incidence of anemia and recommended checking the full blood count at 20–24 weeks to identify women who may need iron and folic acid supplementation.
There is no evidence in the literature to inform specific advice about other lifestyle issues, e.g., work patterns, sexual activity and exercise in multiple pregnancy.
Use of corticosteroids
It is well known that antenatal corticosteroids reduce neonatal complications in preterm babies. Even though it is thought that corticosteroids are less effective in multiple pregnancy the question arises, given the substantial risk of preterm delivery in multiple pregnancy, as to whether giving an untargeted course of steroids routinely at a given gestation or whether giving multiple courses at regular intervals may be beneficial. The problem with giving a single course routinely would be that the time of administration may be remote from delivery and the effect dampened. Multiple courses are associated with potential harm, i.e., lower birthweight and reduced head circumference. On this basis, it is better to avoid untargeted routine single or multiple courses of steroids and to advocate targeted steroids when indicated, i.e., when preterm labor or birth is imminent, and therefore to shift the focus towards informing all women with twin and triplet pregnancies of the increased risk of preterm birth and the benefits of targeted steroids, and provide information about symptoms and signs to be aware of so that they can present in a timely manner.
Timing of delivery
Up to 60% of twins and more triplets and higher order pregnancies deliver preterm (i.e., before 37 weeks’ gestation). For those that are undelivered, appropriate timing of delivery is aimed at optimizing gestation but avoiding stillbirth. For triplets and higher orders, it is rare to get beyond 35 weeks’ gestation. Epidemiologic studies show that perinatal mortality of twins increases significantly after 37 weeks’ gestation. Therefore, for uncomplicated twin pregnancies delivery should be considered from 37 weeks’ gestation. Slightly earlier delivery is advocated for monochorionic diamniotic (MCDA) twins because even in uncomplicated MCDA twins, the risk of stillbirth is higher than dichorionic twins at all gestations, and on balance of risks, given advances in neonatal care, earlier delivery seems logical. A systematic review concluded that elective delivery from 36 completed weeks may be the best current strategy to decrease fetal mortality in MCDA twins[5]. The important point to make is that uncomplicated MCDA twins do not need to be delivered before 36 weeks’ gestation, and if uncomplicated and the woman wishes delivery could be considered after 37 completed weeks (bearing in mind the risk of stillbirth and consequences remains present).
The UK NICE guideline recommends delivery of dichorionic twins from 37 completed weeks’ gestation, monochorionic twins from 36 completed weeks’ gestation and triplets from 35 weeks’ gestation[4].
Timing of delivery for monoamniotic twins will be discussed later in this chapter.
Mode of delivery
With regard to absolute indications for cesarean section (CS), it is generally recommended that monoamniotic twins, conjoined twins and triplets or more are delivered by elective CS[6]. Also, most clinicians would advise that if the first twin is nonvertex, delivery is by CS; this is partly due to the findings of the term breech trial[7] (although that trial applied to singleton pregnancy) and concerns about the rare complication of locked twins, which carries a high mortality rate. There is now good evidence from a large international multicenter randomized trial (Twin Birth Study)[8] – 2804 uncomplicated twin pregnancies where the leading twin was vertex recruited after 32 weeks’ gestation and randomized to planned vaginal birth versus planned CS – that planned elective CS is not advantageous for the fetuses, and this finding applies to both dichorionic and monochorionic diamniotic twins. The authors did emphasise requirements to optimize outcomes were that the deliveries were carried out by skilled clinicians, particularly in vaginal breech delivery (if the second twin nonvertex), and there was access to facilities for emergency CS without delay. The evidence to guide mode of delivery for preterm twins <32 weeks is not robust and conflicting. There is some evidence to support CS when the fetal weight range is 500–1500 g; however, vaginal delivery is an acceptable practice if the first twin is vertex until more robust data come available[7].
Prevention of preterm labor and delivery
Interventions that have been studied to prevent spontaneous preterm labor, and hence delivery, in twin and triplet pregnancies include bed rest, progesterone (intramuscular or vaginal), cervical cerclage and tocolytics (oral betamimetics). Sexual abstinence has never been studied in multiple pregnancy.
A systematic review of seven RCTs (five of twins, two of triplets) of bed rest found no evidence to support this intervention to reduce preterm delivery[9].
Several RCTs have evaluated the clinical effectiveness of progesterone (intramuscular or vaginal) versus placebo in the prevention of preterm birth in women with twin and triplet pregnancies. None have shown this intervention to be effective[4]. A systematic review and meta-analysis of individual patient data from five RCTs considering the impact of vaginal progesterone in women with asymptomatic short cervix (defined as 25 mm or less on midtrimester ultrasound) included only 52 twin pregnancies[10]. Whilst there was a significant reduction in preterm birth in singleton pregnancy, there was no such effect in twin pregnancies. However, there was a reduction in composite neonatal morbidity and mortality, and it is believed that these findings need to be confirmed in a prospective randomized trial of progesterone for women with twin pregnancy and short cervix[11].
One RCT and one observational study (prospective) of twin pregnancies and four observational studies (retrospective) of triplet pregnancies evaluated the effectiveness of cervical cerclage in the prevention of preterm birth. None showed this intervention to be effective[4]. More recently, the cervical pessary (Arabin pessary) has been studied in women with short cervix and while the preliminary results are promising, results of appropriately powered trials are awaited[11].
A systematic review of five RCTs evaluating the effectiveness of betamimetics found no evidence to support this intervention to reduce preterm delivery[12].
Therefore, in the absence of an effective intervention routine screening to predict, preterm delivery is not recommended in twin and triplet pregnancy. There is no evidence to guide management in higher order pregnancies or for those who have twin and triplet pregnancies and have other risk factors apart from the multiple pregnancy, and therefore this management should be individualized.
Management of complicated multiple pregnancy
Discordant fetal anomaly
Fetal anomalies are more common in twins and higher order pregnancies compared with singletons. In monochorionic twins, the rate of structural anomaly is even higher although discordant aneuploidy is very rare. If the abnormality is associated with chromosomal abnormality, invasive prenatal diagnosis may be offered. Invasive prenatal diagnosis in multiple pregnancy should ideally be undertaken by a specialist who has the expertise to undertake selective reduction should the need arise as it is very important, particularly where there are no obvious features to identify the abnormal fetus, that the pregnancy is carefully mapped. If the condition is severe or lethal, selective termination of pregnancy is an option, but the technique used will depend on whether there is shared placentation.
In dichorionic twins where selective termination is planned, fetocide using medical therapeutics can be undertaken. It is recommended that this is either undertaken before 14 weeks’ gestation or after 32 weeks’ gestation. This is because, if undertaken before 14 weeks’ gestation, the outcomes are better, in particular gestation at delivery of the surviving normal fetus[13]. Therefore, if the window of opportunity to intervene before 14 weeks is lost, the delay until 32 weeks is advocated to afford the normal fetus the best chance of a normal outcome. This can be a very difficult concept for couples and requires expert counseling and good emotional support. If the woman insists on selective reduction before 32 weeks, she needs to be aware of the risks to the normal fetus of preterm delivery secondary to procedure-related ruptured membranes, infection and preterm labor.
In monochorionic twins, as the fetal circulations are connected, selective termination cannot be undertaken with medical therapeutics because of the risk of death and neurologic damage to the co-twin. Invasive techniques, such as cord occlusion or interstitial ablation, are required and these techniques are challenging, high-risk procedures and require specific expertise.
Discordant fetal growth
In dichorionic twins where there is growth restriction in one fetus, the management in terms of surveillance does not differ from that in singleton fetal growth restriction. However, when timing delivery, the risks for the normal fetus need to be carefully considered. If there is severe growth restriction at extremes of gestation (24–28 weeks), the woman and her partner may need to consider allowing the growth-restricted fetus to die in utero to gain optimal gestation and outcome for the normal fetus. Monochorionic twin growth discordance will be addressed later in this chapter.
Single fetal death
Single fetal death in the first trimester is relatively common and is termed “vanishing twin syndrome.” It is a low-risk situation for the surviving fetus and the woman, and her family can be reassured that there are unlikely to be long-term consequences. The ongoing pregnancy can be treated as a routine singleton pregnancy.
After the first trimester, single fetal death is a high-risk situation for the surviving fetus in monochorionic and dichorionic twin pregnancy. The risks are, however, much higher for monochorionic twins. A systematic review of 22 studies showed that the rates of co-twin death, preterm delivery, abnormal postnatal cranial imaging and rate of neurodevelopmental impairment after single fetal death were 15%, 68%, 34% and 26% in monochorionic versus 3%, 54%, 16% and 2% in dichorionic twins[14]. Monochorionic twins will be discussed below. What is unclear is whether preterm delivery was spontaneous or iatrogenic, and if iatrogenic what the indication for delivery was. Therefore, some of the morbidity in dichorionic twins may be secondary to clinicians deciding to deliver the surviving fetus preterm for fear of it succumbing to the unknown pathology that caused one twin’s death, and the morbidity secondary to preterm delivery.
In current practice in dichorionic twins, if there is co-twin demise, delivery is not recommended unless there are signs of surviving twin compromise (e.g., abnormal cardiotocography (CTG)). There is no evidence to guide ongoing monitoring in this situation but it seems sensible to undertake a CTG at the time of single death diagnosis (only at a gestation where CTG is advocated, i.e., not before 24–26 weeks), and thereafter, if clinically indicated, e.g., reduced fetal movements. Continuing the pregnancy to afford a better gestation can be difficult for the anxious woman, her partner and family, and in addition to requiring emotional support, regular clinical review including ultrasound at least every 2 weeks is advocated.
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