This was an interesting abstract, which makes me want to read the full article. The objective was, “To estimate the gestational age ranges that result in optimal birth outcomes for each of four risk-defined groups.” What was most intriguing to me is that this is the first time I’ve seen an attempt made to look at “the best time for birth” for different risk groups, rather than putting everyone in the same category. The problem that occurs sometimes is that if there isn’t a proper delineation by risk factors, is that everyone gets “tarred by the same brush.” For instance, it’s known that smoking causes health problems for all people, including second-hand smoke in children, and maternal smoking in fetuses and neonates. I’ve previously talked about the risk of maternal smoking for babies — the infant mortality rate for the year 2000 was 10.7/1000 for smokers but 6.5/1000 for nonsmokers. If a study that looks at infant mortality rate doesn’t take into account maternal smoking, it may reach the wrong conclusion. Let’s say that a study looking at maternal hypertension and neonatal mortality finds that maternal hypertension increases the rate of neonatal mortality, but it didn’t look at only women who smoke or women who don’t smoke, or didn’t properly adjust the risk of neonatal mortality based on the known risk factor of smoking. The study may wrongly conclude that maternal hypertension alone may raise the risk of neonatal mortality X%, when the real cause of much of the increased risk is maternal smoking, and maternal smoking increases the risk of maternal hypertension and also neonatal death.
I’ve seen some people say that “the best time” for a baby to be born is 39 weeks, based on different factors (the people who have said that haven’t linked to studies, and I’m not sure I’ve read them, so I don’t know how they determine that — whether the “best” time is due to how many women have C-sections versus vaginal births, or perinatal deaths, or what), although I have recently read and blogged about a study that shows that elective C-sections at 37 and 38 weeks increase problems with neonatal morbidity compared to those done at 39 weeks. This study indicates that 39 weeks may not be the best for individual risk groups even if (and that’s a big “if”) it may be the case for the entire United States as a whole.
The restrospective study divided the women into four risk groups — the regular or low-risk group, maternal hypertension, advanced maternal age, and diabetic women — then looked at various outcomes (NICU admissions, Apgar scores, C-sections, etc.) to see which births on which gestational days had the best outcomes based on the day. The results were intriguing:
- The low-risk group OTD (optimal time of delivery) was calculated to be 37 weeks 1 day to 41 weeks 0 day
- the advanced maternal age group OTD was 38 weeks 5 days to 39 weeks 6 days
- the hypertension group OTD was 39 weeks 2 days to 40 weeks 1 day
- and the diabetes mellitus group OTD was 40 weeks 3 days to 41 weeks 1 day.
So it doesn’t appear that low-risk women should be offered an induction or C-section at 39 weeks, nor should the scare tactics start at going past 40 weeks 0 days, like it sometimes does. What is most interesting to me is that the DM group has better outcomes if the birth happens after the due date, but this seems to be the group that is typically induced or sectioned due to their risk status — typically “big baby” fears. But this seems to reject that notion. And the other two groups seem to do better closer to their due dates, but many women are induced (or offered an induction or C-section, or the doctors don’t turn down requests for inductions) at 37 or 38 weeks, because “well, you’re ‘term’ now so the baby can safely be born now, with no problems, and aren’t you tired of being pregnant?” In fact, it appears from these numbers that only babies born to low-risk moms do well if born in the first week and a half of term — that perhaps babies born to these higher-risk mothers benefit from more “womb time” than low-risk babies. Interesting.
Filed under: studies & stuff Tagged: | advanced, ama, baby, birth, C-section, cesarean section, childbirth, diabetes mellitus, gd, gestational diabetes, hospital birth, hyptertesion, induction, maternal age, maternal hypertension, nicu, pregnancy, pregnant