When the study titled Elective birth at 37 weeks of gestation versus standard care for women with an uncomplicated twin pregnancy at term: the Twins Timing of Birth Randomised Trial came out on June 13, 2012 both the BJOG:An International Journal of Obstetrics and Gynaecology in their press release: “BJOG release: Elective birth at 37 weeks gestation safer for mothers carrying uncomplicated twins, new research suggests” and Science Daily: “Earlier Birth, at 37 Weeks, Is Best for Twins, Study Suggests” reported the findings as strong evidence to support NICE’s (National Institute for Health and Clinical Excellence) guidelines.
“The findings of our randomised trial support the recent NICE recommendations. For women with an uncomplicated twin pregnancy at 37 weeks of gestation, elective birth was associated with a significant reduction in the risk of birthweight below the third centile, with no identified increase in the risks associated with early birth for either women or their infants.”
So what are the NICE recommendations?
- 22.214.171.124 Inform women with uncomplicated monochorionic twin pregnancies that elective birth from 36 weeks 0 days does not appear to be associated with an increased risk of serious adverse outcomes, and that continuing uncomplicated twin pregnancies beyond 38 weeks 0 days increases the risk of fetal death.
- 126.96.36.199 Inform women with uncomplicated dichorionic twin pregnancies that elective birth from 37 weeks 0 days does not appear to be associated with an increased risk of serious adverse outcomes, and that continuing uncomplicated twin pregnancies beyond 38 weeks 0 days increases the risk of fetal death.
Let’s take a more in-depth look at the study. This is a randomized control trial where women with twin pregnancies were selected by phone to either be placed in the “standard care” bucket or the “elective birth” bucket. The goal of the study was to determine if an uncomplicated twin pregnancy delivered at 37 weeks gestation reduced the risk of death or serious outcomes for babies without increasing harm.
We do know that multiple pregnancies come with unique complications that singletons do not, such as high rates of prematurity, cerebral palsy, developmental delays and intrauterine growth restriction (IUGR) among others. Credit where credit is due, this study does not compare twins to singletons. The authors maintain an apples-to-apples comparison by only looking at twins. The researchers were specifically looking to see if elective birth (both induction and cesarean section) would reduce the risks of perinatal mortality, birth trauma, lung immaturity and admission to the NICU, necrotizing enterocolitis and systemic infection.
For the mothers, they looked at pre-eclampsia, eclampsia, protein-uria, renal insufficiency, liver disease, neurological disturbances, hematological disturbances, antepartum hemorrhage and abnormal umbilical artery. They also looked at a number of labor and birth complications. However, the focus of the study was primarily the infants, not the mothers.
“Multiple pregnancy is associated with both maternal and fetal complications. While women with a twin pregnancy are more likely to give birth prematurely, approximately 46% will give birth after 37 weeks’ gestation. For women whose twin pregnancy continues beyond 37 weeks’ gestation, there is a higher risk of perinatal mortality and morbidity with advancing gestational age.
The Australian study looked at 235 women with an uncomplicated twin pregnancy at 36 weeks gestation. They were divided into women who planned an elective birth from 37 weeks (elective birth group) and women who planned birth from 38 weeks (standard care group).”
One problem I encountered was the relatively small sample size of 235 women. The authors admit there should have been closer to 1100 mothers to validate their findings:
“There are several limitations to our findings. The current trial was stopped before completion of the estimated sample size for a lack of ongoing funding. We are therefore relatively underpowered to assess our primary outcome of serious adverse outcome for the infant, as well as uncommon maternal labour and birth complications. To detect a 66% reduction in adverse outcome at term as suggested using plurality-specific data would require a sample size of approximately 1100 women with an uncomplicated twin pregnancy at term.”
Another problem I encountered while looking at the data was that the gestational age of the “Elective Birth” babies was roughly the same as the “Standard Care” babies, differing by only 0.5 weeks.
“Despite our trial protocol specifying birth for women in the Standard Care Group being after 38 weeks of gestation, and as close to 39 weeks as possible, 45% of women in this group gave birth between 37 and 38 weeks of gestation, reflecting the practicalities of scheduling induction of labour and caesarean section procedures in a busy maternity environment at close to 38 weeks of gestation. The resultant mean difference of 4 days in gestational age at birth is consistent with the identified difference of 90 g in mean birthweight. However, these identified differences do not explain the significant reduction in the risk of birthweight less than the third centile observed in the Elective Birth Group, raising the possibility that this was a chance finding.” (emphasis mine)
But, yet, one of the main reasons they suggest elective birth at 37 weeks is due to IUGR or small for gestational age. Out of the “Elective Birth” group, 7 babies were in the third percentile or less (3%), the “Standard Care” group had 24 babies (10.1%). On the surface, that is much higher. However, the “Standard Care” numbers also accounts for emergency cesarean sections and induced labors for medical reasons. For ethical reasons unplanned inductions and cesarean sections needed to occur.
The questions I have are: how badly did that skew the data? How accurate is the gestational age of the babies? There is no indication in the study to tell us that these pregnancies were accurately dated via early ultrasound, etc. so some amount of variability in gestational ages may have impacted results.
How is elective twin birth managed here in the U.S.?
In the American Congress of Obstetricians and Gynecologists’ ACOG Practice Bulletin #56, 2004, reaffirmed in 2009
“The nadir of perinatal mortality for twin pregnancies occurs at approximately 38 completed weeks of gestation and at 35 completed weeks of gestation for triplets; the nadir for quadruplet and other high-order multiple gestations is not known. Fetal and neonatal morbidity and mortality begin to increase in twin and triplet pregnancies extended beyond 37 and 35 weeks of gestation, respectively. However, no prospective randomized trials have tested the hypothesis that elective delivery at these gestational ages improves outcomes in these pregnancies.”
At this time, ACOG is not recommending elective birth at 37 weeks for twins. The data that ACOG provides reflects the same information as NICE and as in the BJOG study. So the data set is the same, it’s the recommendations for scheduled birth at 37 weeks that differ.
The March of Dimes makes no distinction between singleton and multiple gestation pregnancy with regards to their campaign, Healthy Babies are Worth the Wait™ to prevent prematurity. “In 2010, the Joint Commission established a new perinatal care core measure set that includes the number of elective deliveries (both vaginal and cesarean) performed at > 37 and < 39 weeks of gestation completed.” I speculate that is because of the relative rarity of twin births in relation to singletons. Although I’d like to see a future statement specifically on twins in this regard.
“Lamaze Healthy Birth Practice #1 – Let Labor Begin on Its Own” would appear to be in conflict with the BJOG study and NICE’s recommended practices. However, there is always an exception for a true medical need. Induction and scheduled cesarean sections, when used judiciously, are lifesaving for both mother and baby. Professor Jodie Dodd, one of the researchers in the BJOG study, believes strongly in her results. So much so, that she and the Univeristy of Adelaide put out this video regarding her findings.
Even with a smaller sample size than required for a full analysis, this study, plus previous others, as cited in the references, shows a correlation between birth at 37 weeks for twins and reduced risk for low birth weight and perinatal mortality. As a Lamaze educator, I feel an internal conflict with the March of Dimes information, Lamaze’s Healthy Birth Practice #1 and the study results. My belief is that all babies know their best time to be born, including twins. I think that every twin pregnancy should be taken on a case by case basis. Truly, there are increased risks with any twin pregnancy. However, the risks always need to be explained in context of the long term effects of a scheduled birth on breastfeeding; cesarean section complications; and long term complications of prematurity on the babies. As long as the mother has the full set of information she can make an appropriate decision with her individual care provider regarding scheduling the elective birth of her twins.
This post was written by regular contributor, Deena Blumenfeld, RYT, RPYT, LCCE To read more about Deena or to contact her, please see our contributor page.