37 weeks is becoming the due date for twins- which is actually considered too early for an elective induction or c-section for singletons. There’s a reason for this. In 2016 a large, international study came out saying that allowing twin pregnancies to continue to 38 weeks dramatically increased the chances of still birth.
But if you have been in the home birth community for a while, you may have heard stories of a few rare moms who had home births twins at 39 or 40 weeks. There are some stories here.
It’s an interesting divide.
Who is “right”?
Well, first of all, I don’t think this subject is about getting the right answers. I think it’s actually about asking the right questions.
It’s A BIG Study. Is That a Good Thing?
The authors said they included all studies in the “Medline, Embase, and Cochrane Library using the NHS Evidence website and Cochrane online library platforms from inception until December 2015 for studies on twin pregnancies that reported rates of stillbirth.” The studies reviewed in this study covered different countries. They looked only at dichorionic pregnancies- twin pregnancies where the babies each had their own placenta. (Monochorionic-monoamniotic pregnancies are rarer and known to carry additional risks. These occur only in identical twins.)
This study did very little to limit confounding variables. Confounding variables are these darling little factors that suggest correlation when there isn’t any. In this case, the confounding variables include:
- Monozygotic (identical) vs. dizygotic (fraternal) twin pregnancy- monozygotic twins are considered to have more risks than dizygotic twins.
- Spontaneous (no fertility treatments) vs. conceived with fertility treatments.
- Age of mother (moms over 40 have a higher likelihood of twins, but also a higher risk of complications. Moms under 18 have higher rates of complications as well).
- Nutritional deficiencies such as anemia or iodine deficiency- especially important if any of the included studies came from developing countries.
- What type of prenatal care women were receiving, in fact the authors were aware of this variable and its potential for confounding and state that “The variation observed in the clinical management of twin pregnancies and neonatal care after delivery between centres could also have influenced the outcomes.”
- Any pre-existing conditions the mothers may have had.
So because there was so little control for confounding variables, the authors of this study are like, “Oh gee! ALL twin pregnancies are at risk for stillbirth at 38 weeks!!!”
Twins at Home vs. Twins in the Hospital
In the few places where midwives are able to deliver twins (a number which is dwindling), the twin pregnancy would have to go past 37 weeks or the midwife would not be allowed to attend. So accounts of mothers who have had home births of twins are already in a different situation with gestation than many mothers who have delivered in a hospital. These are anecdotal accounts and there are very few- but I still think they are an interesting phenomenon to consider.
Mary Cronk, a British midwife with over 45 years of experience and who has delivered several sets of twins advises mothers that identical twins generally carry more risks. (You can read her guidelines for midwife care of twins at the above link.)
However, there are a few very rare cases of identical twins born at home in the 20th century, midwife Jeanine Parvati Baker’s being one of them. (I don’t know of any online publications of her twin birth but you can read about it in Elizabeth Noble’s Having Twins and More and Jeanine’s book Prenatal Yoga and Natural Birth.)
An interesting side note is that her twins were considered at risk for being “locked twins” because Baby A was in breech and Baby B was vertex. However, Jeanine didn’t have many of the other risk factors for locked twins such as small babies, first birth, oligohydramnios, uterine hypertonicity, early rupture of the second sac (and I think her twins were dichorionic). Her babies were born at term and healthy and lived to adulthood.
On the other hand, the study in the BMJ acknowledged that one of its limitations was that recommendations of delivery for twins have varied between 34 and 38 weeks- which means that some pregnancies that may have gone longer didn’t because a delivery was scheduled earlier. And as, the authors point out, because of the high rates of pre-term delivery (both spontaneous and planned) they had a smaller sample size of births going to 37 and 38 weeks. And a smaller sample size means that any anomaly can throw the numbers off. (One death in ten looks riskier than one in a thousand- even if that one in ten was a fluke.) So the bottom line is that we have very little good data on what it would mean to carry a twin pregnancy to 39 or 40 weeks because it doesn’t usually happen in a hospital setting and midwives attend very few twin births.
Are We Asking The Right Questions?
So the 2016 BMJ study merely found an average across a VERY broad spectrum of twin pregnancies and has urged that delivery for all twin pregnancies be based on this average.
But I don’t think the question should be “How can we schedule the delivery to avoid preterm complications and stillbirth?”
The question should be, “How do we get more precise about predicting which pregnancies are at risk of stillbirth?” Since delivery at 37 weeks can cause an increased incidence of issues like respiratory problems, are there some twin pregnancies that could go full-term without risk to the mother and babies? And along with that, how can we prevent preterm labor and delivery of twins? Shouldn’t we be looking for how we can do better than 37 weeks?