New methods have been sought to improve the accuracy of fetal weight estimation such as three-dimensional ultrasonography. In the early s, Lee et al. This method has the advantage of reducing the time spent to perform the test, maintaining a good accuracy for the estimation fetal weight. In general, the accuracy of estimation weight in twin pregnancies is worse than single pregnancies.
Biometric measurement of these fetuses in the third trimester is greatly impaired due to the technical difficulty of examination. Although evaluation of fetal body volume through the use of magnetic resonance imaging is still considered an expensive method, there is good accuracy in fetal weight estimation, besides being a good predictor in the diagnoses of small fetuses for gestational age when compared to two-dimensional ultrasonography [ 28 ].
Estimating weight in twin pregnancies remains a challenge. New research needs to be conducted in search for new methods in order to improve accuracy. Fetal weight should not be considered when both fetuses are cephalic.
In those cases, regardless the fetal weight, a vaginal delivery can be attempted. Most studies showed worst perinatal outcomes for vaginal deliveries when the second twin was non-cephalic and under g [ 29 , 30 ]. Weight difference is related to worst neonatal outcomes, regardless the delivery mode [ 31 ], and also to unsuccessful attempt of labor [ 32 ].
A previous cesarean delivery is considered a risk factor for an emergency C-section after attempting a vaginal delivery in twin pregnancies [ 34 ]. Regardless, a caution trial of labor can be a safe option in those patients, when the first twin is cephalic [ 35 ].
On the other hand, patients with two or more previous cesarean sections should not attempt a vaginal delivery due to higher risk of uterine rupture. There is limited existing evidence to determine the safest mode of delivery for extremely preterm twins. Therefore, it is important to consider the fetal presentation and weight when deciding the delivery mode, regardless gestational age. This study found higher rates of maternal complications in growth-discordant twins.
Higher rates of maternal morbidities are found in multiple gestations, compared to singletons. There is a higher risk of pre-eclampsia, diabetes and post-partum complications, as uterine atony and postpartum hemorrhage. Regardless, maternal conditions are rarely an indication of a cesarean section. An elective cesarean delivery can be performed after maternal request, after exposing the risks of the procedure, as longer maternal hospital stay, increased risk of the newborn going to the ICU due to respiratory problems and increased risks for subsequent pregnancies, as placenta previa and uterine rupture [ 37 ].
In those cases, the surgery should be planned to the appropriate gestational age, considering chorionicity and amnionicity.
The preferred delivery route is the cesarean section because vaginal delivery is associated with an increased risk of adverse outcomes if compared with the cesarean [ 41 , 42 ].
In conjoined twins, the data available is based in small case report studies and expert opinion, but what is suggested is the delivery time and mode of the viable ones must be near term cesarean section after confirming lung maturity. In selected cases an EXIT procedure can be performed in order to stabilize the fetuses with cardiac union to examine and close the vessel communication safely [ 43 ].
Another controversial subject about delivery in twins is the time interval between fetuses in vaginal delivery. New guidelines such as the American College of Obstetricians and Gynecologists do not recommend an upper limit to the time interval between fetuses, if the fetal heart rate is reassuring, as some studies also suggests [ 44 , 45 , 46 , 47 ].
However, there are studies that provide evidence of an association, but not necessarily causality, between longer twin-to-twin time interval and poor second twin outcome, such as lower apgar grades and decreasing pH in umbilical arterial blood gas [ 48 , 49 , 50 ]. For the babies, the increased risks are due to being born prematurely or due to complications due to a shared placenta or blood vessels and due to uterine restriction.
It is important to know whether your twins are sharing a placenta, as sharing a placenta also means sharing the blood supply from the mother. If the sharing of the blood supply is unequal, this can lead to complications. For this reason, women carrying twins sharing a placenta will need to have more frequent antenatal check-ups. Twins sharing an inner membrane which means they share the amniotic sac carry an even higher risk of complications, as there is the potential for their umbilical cords to become tangled and to cut off their blood supply.
In this case the pregnancy is monitored even more closely, and it may be recommended that your twins be delivered earlier. Around two in three sets of twins are fraternal. Dizygotic twins each have their own placenta, inner membrane and outer membrane. These babies will be no more alike than siblings born at separate times. The babies can be either the same sex or different sexes. Triplets and more can be a combination of both identical and fraternal multiples.
Triplets are most commonly a combination of monozygotic and dizygotic, with a set of identical twins two and a fraternal one triplet. Triplets or more require a closely monitored pregnancy. The normal length of gestation period of time spent developing in the womb for a single baby is around 40 weeks.
However, gestation for twins, either identical or fraternal, is usually around 38 weeks. As twins are usually premature, they are more likely to have lower birthweights. Prematurity is associated with increased risk of a number of disorders, including jaundice. Like in any pregnancy, if you are pregnant with twins or multiple babies, eating well and getting enough rest are the cornerstones of good self-care.
Aim for healthy, balanced meals and drink plenty of fluids, ideally at least eight large glasses of water a day. Sugary snacks can give you highs and lows, which may feel unpleasant. Your body will be needing extra protein, calcium, iron, iodine, vitamin D, 2 folic acid and vitamin B12 than if you were only having one baby, so make sure your diet is varied. Try to eat little and often. About one third of all twins are born vaginally and the process is similar to that of giving birth to a single baby.
If you're planning a vaginal delivery, it's usually recommended that you have an epidural for pain relief. This is because, if there are problems, it's easier and quicker to assist the delivery when the mother already has good pain relief.
If the first twin is in a head down position cephalic , it's usual to consider having a vaginal birth. However, there may be other medical reasons why this would not be possible. If you have had a previous caesarean section, it's usually not recommended you have a vaginal birth with twins. If you have a vaginal birth, you may need an assisted birth , which is when a suction cup ventouse or forceps are used to help deliver the babies. Once the first baby is born, the midwife or doctor will check the position of the second baby by feeling your abdomen and doing a vaginal examination.
If the second baby is in a good position, the waters will be broken and this baby should be born soon after the first as the cervix is already fully dilated. If contractions stop after the first birth, hormones will be added to the drip to restart them. You may choose to have an elective caesarean from the outset of your pregnancy, or your doctor may recommend a caesarean section later in the pregnancy as a result of potential complications.
The babies' position may determine whether they need to be delivered by caesarean section or not. If the presenting baby - the one that will be born first - is in a breech position feet, knees or buttocks first , or if one twin is lying in a transverse position with its body lying sideways , you will need to have a caesarean section. Some conditions also mean you will need a caesarean section; for example if you have placenta praevia a low-lying placenta or if your twins share a placenta.
If you have previously had a very difficult delivery with a single baby, you may be advised to have a caesarean section with twins.
Even if you plan a vaginal birth, you may end up having an emergency caesarean section. In very rare cases, you may deliver one twin vaginally and then require a caesarean section to deliver the second twin if it becomes distressed. After the birth, your midwife will examine the placenta to determine what type of twins you have. Twins can either be fraternal or identical. Depending on where you plan to give birth, you may need to go to another hospital with appropriate facilities if complications in your pregnancy indicate you're likely to have an early delivery.
This may not be near to home, so make sure to check there are enough beds for both your babies in the neonatal unit. Ask if your chosen hospital has a transitional care unit or a special care nursery. Of the 14 s twins with a composite primary outcome there were two cases of perinatal mortality. One was a case of intrapartum death after breech extraction at 34 weeks of gestation, where the obstetrician was unable to deliver the head twin-to-twin time interval 29 min and one was a second twin born at 33 weeks of gestation twin-to-twin time interval eight minutes who developed NEC at four days of age, underwent major surgery and died shortly thereafter.
The remaining 12 s twins with composite primary outcomes had severe metabolic acidosis. One of these neonates, born at 38 weeks of gestation, was admitted to NICU for five days because of transient tachypnea of the newborn TTN. The other 11 recovered within 15 min. There were two pregnancies diagnosed with TTTS included in the study. No other complications occurred. Twin-to-twin time interval had a significant impact on the composite primary outcome for the second twin Table 4.
The composite secondary outcome occurred in Median twin-to-twin time interval, 21 3— min vs. Composite primary and secondary outcomes are shown in relation to the stratified twin-to-twin time intervals in Fig. Composite secondary outcome occurred in The composite primary outcome occurred in 1.
There was no difference in composite primary or secondary outcomes according to presentation cephalic or breech and intertwin delivery interval. Figure 2 shows the correlation between arterial umbilical pH and twin-to-twin interval time. Umbilical cord arterial pH in the second twin related to twin-to-twin delivery time interval in minutes.
The mode of delivery for the second twin in relation to twin-to-twin time interval is shown in Fig. This study reaffirms previous evidence that the second twin is at greater risk of metabolic acidosis and neonatal morbidity than the first twin [ 3 , 6 , 12 , 18 ].
We were able to confirm that there is an association, but not a clear causality, with the twin-to-twin time interval [ 11 , 12 ]. Only 14 of the second twins had a composite primary outcome but they had significantly longer median twin-to-twin time intervals than second twins without a composite primary outcome. Second twins with a twin-to-twin time interval of more than 30 min had higher rates of primary composite outcomes than second twins born within 30 min. No differences were seen in composite secondary outcomes that related to twin-to-twin time intervals.
Previous studies have come to varying results on the possible impact of twin-to-twin time interval on neonatal outcome for the second twin [ 9 , 11 , 13 ]. Most studies imply that considering the fact that umbilical cord pH decreases with longer duration of the delivery of the second twin, it is important to apply active management to keep the twin-to-twin time interval as short as possible, ideally below 30 min.
Leung found that pH deteriorates faster in the second twin than in the first twin [ 19 ], and recommend a fast delivery of the second twin. In this study we found a significantly higher rate of metabolic acidosis and lower mean arterial pH in second twins born after a twin-to-twin time interval of 30 min than in second twins born within 30 min.
However, there was no difference in Apgar score, the differences in pH were small and most of the second twins with metabolic acidosis recovered quickly. The two cases of perinatal mortality occurred in second twins born within 30 min. Furthermore, there was no difference in neonatal morbidity, and admission to NICU was not associated with twin-to-twin time interval.
Although the small difference in pH-levels in umbilical blood gas 7. In this study there was a combined vaginal-cesarean delivery in 35 cases 6. Cesarean delivery of the second twin is considered to be the least desirable mode of delivery and should be avoided [ 4 , 6 ] due to possible complications for both mother and child. Studies have shown a worsened outcome, with increased physical and psychological maternal morbidity [ 18 , 21 ] as well as higher neonatal morbidity [ 4 , 6 ].
Twenty eight of these 35 combined vaginal-cesarean deliveries occurred in the twin-to-twin time interval of more than 30 min, 17 in the interval of more than 60 min.
This is in agreement with previous studies that have found a six-fold increased risk of combined vaginal-cesarean delivery after 30 min and an eight-fold increased risk after 60 min [ 4 ].
Our study does not show any differences in primary and secondary neonatal outcome related to CS. However, maternal physical and psychological morbidity was not analyzed. The fact that most combined deliveries occurred in the group where the twin-to-twin delivery time interval was more than 30 min, is in itself not surprising. If the second twin is not spontaneously delivered, the risk of assisted delivery increases over time. Previous studies have found that combined vaginal-cesarean twin delivery can be avoided with active management in the second stage of delivery of the second twin [ 22 ].
Active management is generally considered to be internal podalic version IPV followed by breech extraction of the non-vertex and the unengaged vertex second twin. Previous findings suggest that IPV may be more successful than external version when it comes to vaginal delivery, and with better neonatal outcome [ 1 , 22 , 23 , 24 ].
External version has been found to be associated with complications such as fetal distress, cord prolapse and compound presentations [ 25 ]. However, this maneuver was only performed in 10 cases, of which nine were successful. Active management is not praxis at our unit and unfortunately the IPV maneuver is therefore seldom taught to junior obstetricians. A decreasing rate of IPV and breech extraction, and an increased rate of CS, has also been seen in recent years in several other countries around the world [ 24 ].
In the Danish register study a better neonatal outcome was seen for the second twin after IPV and extraction than after a CS [ 24 ]. If an upper time limit is to be advocated, the management of the delivery of the second twin would need to be more active than what is recommended at our unit today.
Without adequate knowledge of, and training in, active management the clinical outcome of such a change in strategy is unknown. Our unit is able to monitor both twins simultaneously and continuously. We also have h in-house pediatric and anesthesia coverage and immediate availability for performing emergency CS. This may partly explain the few primary outcomes. Because of this the results of this study cannot be extrapolated to other units with other preconditions.
It is important for every unit delivering twins to look at their results and from this stipulate guidelines that are in accordance with their preconditions. Factors such as the level of experience of the obstetrician in charge at the delivery, the skill of intrauterine manipulation and the wish of the women giving birth, may all influence the twin-to-twin delivery time interval.
Results from the Twin Birth Study showed that the maternal preference is for vaginal birth, therefore skills need to be maintained [ 26 ]. The limitations of the study are, as in all retrospective studies, that we have no control over available information.
0コメント