umbilical arterial pH-- need research help

[christyc]

I've been doing some research on twin birth, and have come across studies referencing intertwin interval and negative outcomes, and keep finding statements such as:

"In multivariate analysis, only intertwin birth time predicted umbilical cord pH. Arterial/venous pH decreased linearly at a rate of 0.00063 and 0.00081 U/min.... Our study confirmed that longer intertwin birth time is associated with a continuous slow decline in umbilical cord pH...."

"Increasing time interval was related to a decline in the mean umbilical arterial pH and base excess, and fetal acidosis, ..."

"The umbilical arterial blood gas status of the second twin worsened with increasing twin-to-twin delivery interval, and pathologic fetal acidemia (pH<7.0) might develop in the second twin when the twin-to-twin delivery interval was greater than 20 minutes."

So, I'm not a moron, and I get the general gist that the longer the time between twins, the greater the tested risks. I don't know yet if they controlled for things regarding active management of the 2nd twin (such as whether or not 2nd twins had increased pitocin to rush them, other obstetric management or interventions), but I'll be looking into that.

My main questions for now are about the pH. What is normal umbilical arterial pH? How can a lowered pH affect the baby (like what are the symptoms or long-term complications it can cause)? Is it a temporary thing that resolves on its own, or does it require treatment to correct once it happens?

TIA to anyone who has some knowledge in this area!

[mwherbs]

what is the number of twin birth's studied ? are there follow up questions/comments about the article? and what percent of twins are born longer than 20 minutes apart? and what percent of that number had acidosis ?
what was the gestational age range? how many ended in surgical births- what type of anstesia? .... where can I read this article? I have more questions than answers..

[christyc]

Originally Posted by mwherbs

I have more questions than answers..

You and me both! From what I know about natural twin birth, it doesn't make much sense (my own twins were almost 2 hours apart with no adverse effects), so I'm trying to decipher it bit by bit.

Those quotes are actually from the abstracts of several articles on pubmed. All the articles I found about intertwin delivery time indicate that a time longer than 20-30 minutes is associated with lower APGAR and outcomes for twin B, but they differed somewhat on what they recommended. Some said it pointed to active management of the second twin to reduce those negative outcomes, others said it wasn't a big enough deal to change obstetric management.

My husband (who works for a hospital) is going to get me full copies from the medical library sometime this month, and then I'll read the full things. Specifically, I'm curious what kinds of obstetric management of the intertwin interval (pitocin, meds, version, etc.) might have contributed to the outcome other than just the time interval itself.

[mwherbs]

ok so I did a very short search and the most recent article (German) which includes a fairly large # of twin births with the age >34 weeks

this is a key part of their conclusion about timing-- as you can see these factors alone even in a singleton birth are complications and not straight forward births-

"In univariate analysis, breech, transverse lie, birth weight discordance with the second twin > or =20% larger, fetal distress, vaginal operative delivery, and caesarean section were associated with an increased time interval."