When I was pregnant with my son, stillbirth barely even crossed my mind. Once I hit 20 weeks, I was like “bring on the healthy baby!” But since then, I have had 2 friends who had basically full-term stillborn children. (Both were little boys with cord accidents.) And a friend of a friend had a full-term stillbirth (and almost died) after her uterus ruptured during a VBAC.
Between our experiences with pregnancy loss after my son, and my friends’ tragic experiences, and the fact that I’m now older, stillbirth has been on my mind a fair bit. That fear that something bad might happen has been gnawing at me, so I decided to read about stillbirth more to understand it, and potentially avoid activities that could increase the risk… or at least be aware of signs that there could be a problem.
After 20 weeks, a pregnancy loss is considered a stillbirth, not a miscarriage. 24 weeks is considered the line of viability because, theoretically, half of babies born at 24 weeks would survive (many with disabilities, of course). Some studies consider 24 weeks when looking at stillbirths. The causes of stillbirths tend to vary depending on when in the pregnancy they occur, with stillbirths earlier in pregnancy looking a lot more like late-term miscarriages.
Stillbirths are surprisingly common. 1 in 160 pregnancies ends in stillbirth in the US.
This article suggests that the cause for a stillbirth can be probably found about 60% of the time, and possibly or probably found around 75% of the time. (And this article talks about a system for determining causes: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3832680/) Almost a third of stillbirths in their review occurred between 20 and 24 weeks, and 50% occurred before 28 weeks. In their review, the authors found the most common causes were obstetric conditions (29.3%), placental abnormalities (23.6%), fetal genetic/structural abnormalities (13.7%), infection (12.9%), umbilical cord abnormalities (10.4%), hypertensive disorders (9.2%), and other maternal medical conditions (7.8%).
Obstetric complications included abruption (7.4%), complications of multiple gestation (6.1%), and preterm labor, preterm premature rupture of membranes, and cervical insufficiency, often in combination with chorioamnionitis (15.0%). When the baby died during labor (intrapartum stillbirth), it was always categorized as an obstetric complication. Placental abnormalities included uteroplacental insufficiency (4.7%) and maternal vascular disorders (7.6%). (Evidence of placental insufficiency can include fetal growth impairment, oligohydramnios [low amniotic fluid], and preeclampsia.) Placental disorders and hypertensive disorders were more likely with later pregnancy losses, with cord issues occurring more frequency in the latest pregnancy losses. The researchers considered it a cord issue when there was vasa previa, cord entrapment, or evidence of occlusion and fetal hypoxia, prolapse, or stricture with thrombi. They did not include nuchal cord alone to be a probable cause of death because they occur in around ¼ of uncomplicated pregnancies. But the researchers noted that nuchal cords can be harmful, and noted cord issues generally can be, potentially, preventable. They also noted that, after 24 weeks, causes of stillbirth like preterm labor, cervical insufficiency, preterm premature rupture of membranes, chorioamnionitis, and abruption could, instead, lead to preterm birth if the baby could be delivered via C-section.
This article goes through some of the risk factors for stillbirth: increased maternal BMI, advanced maternal age (boo!), smoking (or exposure to smoke), a fetus below the 10th percentile for gestational age (nearly half of stillbirths are below the 10th percentile in weight), mother’s health issues (which account for 10% of stillbirths) such as diabetes (including gestational diabetes), hypertension (4-9% of all stillbirths), hypothyroidism (1% of stillbirths), lupus, and multiple gestation.
It also goes through causes, finding about 6-10% of pregnancies complicated with preeclampsia end in stillbirth. About 3-7% of pregnancies with lupus end in stillbirth. 9.5% of women with recurrent stillbirth have antiphospholipid syndrome. 10-20% of stillbirths are from genetic abnormalities, with anencephaly being one of the more common anomalies leading to stillbirth. Chromosomal abnormalities cause 6-13% of stillbirths, with trisomy 21, 18, and 13 being the most common. With respect to uterine complications, premature rupture of membranes causes about 0.8% of stillbirths, with better outcomes the further into the pregnancy. Chorioamnionitis, the inflammation of the uterus, accounts for 22.6–36.9% of total stillbirths. Cervical incompetence can also cause stillbirth, although a cervical cerclage (which also carries risks) can help. 7.3% of stillbirths involve multiple births. Placental abruption causes 1-4% of stillbirths, and can be caused by trauma, prior cesarean section, hypertensive disorders, parity, maternal age, smoking, and gestational age.
Okay, here’s another one on risk factors. It suggests that the overall stillbirth rate was 4.2/1000 (when only including singleton pregnancies and those without genetic abnormalities), but only 2.4 in pregnancies without fetal growth restriction. Fetal growth restriction (birth weight below 10%), maternal obesity, and smoking accounted for over ½ of the stillbirths. The authors also suggest that only around 15% of stillbirths are unexplained.
The authors focused on “normally formed singletons” (i.e. no twin pregnancies, and no pregnancies with genetic abnormalities) to consider risk factors. They also defined stillbirth as pregnancy loss after the 24th week. In their study, ½ of all stillbirths occurred after 34 weeks.
They had a chart with the stillbirth rate depending on the maternal trait. Younger (under 20) had the highest rates, with older and young (20-24 and 35 and up) the second highest rates. The rates were lowest for moms 30-34. The rates were highest with 0 parity (the number of times a woman has carried a child to a viable age is parity, so parity 0 means never having a child) as well as parity of 3 or more. The lowest was for women 1 parity (like me!).
As we already knew, stillbirth rate increases when mom is heavier. The stillbirth rate was the same for BMI under 24.9, increased super slightly for BME up to 29.9 (although not much, causing the authors to note that even slightly overweight women had lower risks than those who were much heavier) and then rose with BMI above that, the heavier the higher the stillbirth rate.
It also appears that economic insecurity increased stillbirth risk. This study was done in the UK, and found that UK/European women had (much) lower stillbirth rates than those from other countries. Working moms had slightly higher rates (although that could relate to things beyond work, like financial condition). Stillbirth rates were higher if “partner” was not working (again, probably relates to financial condition). They rated an “index of multiple deprivation” and found the most deprived people had the highest rates of stillbirth.
With respect to maternal history, rates were higher with mental health problems, pre-existing hypertension, and cardiac disease. They were MUCH higher in women with pre-existing diabetes (3.7 v. 13.8). And they were much higher with a woman with a previous stillbirth (3.4 v. 11.1).
With respect to pregnancy related factors, smokers had a higher risk than non-smokers (5.8 v. 3.2, although smokers with children without fetal growth restriction was close to the non-smoking mothers) and women who took folic acid has slightly lower risk (3.5 v. 4.7). Alcohol consumption did not have a risk—women who drank had a rate of 3.3 v 3.8 for non-drinkers—yes, the rate for stillbirth was LOWER for drinkers than abstainers. (I highly suspect that this does not show alcohol consumption is good for pregnancy. It might be an economic indicator, as I have seen other studies that suggest very moderate alcohol intake is associated with better child outcomes. That’s likely not because alcohol is GOOD for the pregnancy, just that the women who make the reasonable decision to very occasionally imbibe are, on average, better educated. Take me, for example. Since I got pregnant I have had a few drinks since 12 weeks—a glass of sangria with my family around Thanksgiving, a glass of sparkling wine with friends at a celebratory dinner, and a glass of sangria with friends at a Christmas celebration. And I’ve had maybe a few sips of my husband’s wine or beer over the course of the past 4 months. That has probably added up, grand total, to less than six glasses. Would I call myself a non-drinker? No. Although I certainly don’t think I’m doing anything to harm baby. See more below about alcohol consumption and stillbirth risk.) Likewise “late-booking” an appointment (after 13 weeks) increased the rate of a stillbirth (4.5 v. 3.6). This, too, is likely an economic indicator (or at least an indication of a woman who has not been taking the same care in her early pregnancy).
With respect to pregnancy complications, gestational diabetes increased the risk (4.5 v. 3.7), pregnancy induced hypertension increased the risk a little (3.9 v. 3.7), pre-eclampsia increased the risk a lot (10.3 v. 3.6), and antepartum hemorrhage—bleeding after 24 weeks—increased the risk a lot (3.3 v. 8.7).
With respect to the baby, boys were more likely to be stillborn than girls (4.4 v. 3.9). (This study says the same thing—saying the stillbirth risk for boys is about 10% higher than with girls https://bmcmedicine.biomedcentral.com/articles/10.1186/s12916-014-0220-4 and noting a cause might be “Y chromosome-linked genes are transcribed at the two-cell stage and, in animal models, male embryos have faster development and higher metabolic rates than females, potentially leaving the male fetus more vulnerable to a range of stressors, including endocrine fluctuations, oxidative stress, and nutritional compromise. Recent experimental work in animal models has demonstrated that gene expression in the murine placenta is adaptive and shaped by diet, with placental growth in males being more susceptible to nutritional compromise than that of females”.) Babies in the 10th weight percent were much, much more likely to be stillborn (16.7 v. 2.4 for those in 10-90 and 2.6 for those greater than 90). Fetal growth restriction was also, unsurprisingly, associated with an increased stillbirth rate (2.4 for no growth restriction versus 9.7 for growth restriction detected before birth, and 19.8 for growth restriction not detected until after stillbirth).
The authors found, as I suspected, that women who lived in the most “deprived” areas had an increased risk for stillbirth, as well as those whose partners did not work or who were ethnic or racial minorities.
The authors found that, “Contrary to a systematic review, we found no significant increase in risk of stillbirth with older maternal age. This may be because we excluded congenital anomalies from our cohort, which are known to be increased in older mothers. This is consistent with a recent report which found that the association between stillbirth and maternal age disappears when congenital anomalies are excluded.”
That makes me feel better and worse at the same time. On one hand, I am a (much) older mother, so I do not want to have an increased risk. On the other hand, I’m still worried that there is some congenital abnormality we just don’t know about. Of course, it would be far less devastating to lose a pregnancy to stillbirth if it was because of something like an undiagnosed and un-survivable defect than to lose an otherwise healthy baby. Maybe.
The authors concluded that fetal growth restriction was the single largest risk factor for stillbirth, and that stillbirth is potentially avoidable if those babies are delivered early. That makes me glad I’m having a growth ultrasound at 28 weeks.
Okay, this article is completely crazy—the authors suggest that higher outdoor temperatures increase the risk of stillbirth. Looking at spring/summer stillbirth risks in Quebec Canada (where the temperature fluctuates and women might not be used to heat), “Odds of term stillbirth for temperature 28 °C the day before death were 1.16 times greater relative to 20 °C”.
This article suggests that up to 8% of “unexplained” stillbirths might actually be because of genetic heart defects, which can also cause sudden infant death syndrome.
Going back to the theme of behaviors that might prevent stillbirth, this article suggests that sleeping on your left side might reduce the risk of stillbirth. It found “women who slept on their back or on their right side on the previous night (before stillbirth or interview) were more likely to experience a late stillbirth compared with women who slept on their left side (adjusted odds ratio for back sleeping 2.54…, and for right side sleeping 1.74 …).” The article noted that “The absolute risk of late stillbirth for women who went to sleep on their left was 1.96/1000 and was 3.93/1000 for women who did not go to sleep on their left.” In other words, “Compared with women who went to sleep on the left side, women who went to sleep in any other position had a doubled risk of late stillbirth”. The authors suggest that this position provides the best position for “Cardiac output and fetal oxygen saturation.”
Strangely, it also found that “Women who got up to go to the toilet once or less on the last night were more likely to experience a late stillbirth compared with women who got up more frequently (adjusted odds ratio 2.28 (1.40 to 3.71)).” And “Women who regularly slept during the day in the previous month were also more likely to experience a late stillbirth than those who did not (2.04 (1.26 to 3.27)).” In other words, it’s best to sleep on your left, and at least to try to go to sleep on your left. It’s also better to go to the bathroom more often (?) and it’s better not to sleep during the day. I should note, the authors only considered singleton births of healthy babies (no birth defects). The authors also found, as we’ve previously discussed, that “Women with late stillbirth were more likely to be obese, socioeconomically deprived, to smoke, and be of high parity compared with controls.”
I read this theory—that sleeping on your left side is best—and I’ve been trying to do it every night. It’s horrible. I generally like to sleep on my stomach (a no-go now) or on my back. As far as sides go, I much prefer my right side. But every single night, I try to go to be on my left side. And every single night, I wake up (at least 2-3 times) on my back or right side… because I HATE sleeping on my left side. I can’t explain it. I just don’t like it. I never do it. But I’m going to keep trying.
Okay, I think I previously mentioned that one of my Drs. suggested they might want me to deliver at 39 weeks to decrease the risk of stillbirth? Well, obviously I had to read about that! This article notes that there was a “Rule” that restricts elective delivery before 39 weeks 0 days. It notes that as early-term deliveries decrease, the rate of stillbirth generally increases. Well, to that I just have to say no duh. Of course if you deliver all babies at 39 weeks (not what they’re saying, but making a point), you would decrease the stillbirth rate because you would avoid all stillbirths that would otherwise have happened from 39 weeks to delivery. The question is not whether delivering at 39 weeks decreases the stillbirth rate, it’s what are the risks to the babies delivered early and do those risks outweigh, or not, decreasing the stillbirth risk. If we delivered all babies at 24 weeks, the stillbirth rate would drop a ton, and yet no one is suggesting that’s a good idea. In the author’s defense, I’m not sure they’re taking on the idea that it’s not desirable generally to be delivering at 39 weeks 0 days, just that they think Drs. should have more authority in making the decision unburdened from a “Rule.”
Because I have had 2 friends have basically full-term stillbirths of otherwise healthy babies due to umbilical cord accidents, and because those have been touted as potentially preventable (I’ll have to do another post on kick-counting later), I wanted to read more about them.
This article suggests that a fetus with a heartrate of 90 bpm for 1 minute on a non-stress test should potentially be delivered. It also says the 18-20 week ultrasound should look at the umbilical cord, its characteristics, and its placental and fetal attachment. (Um, isn’t it always attached to the fetus at the belly button?!) Specifically, they want to look for these possible umbilical cord abnormalities:
• Abnormal insertion
• Vasa previa
• Abnormal composition
• Cysts, hematomas and masses
• Umbilical cord thrombosis
• Coiling, collapse, knotting and prolapse
It also notes that “Hiccups occurring daily after 28 weeks, and greater than 4 times per day requires fetal evaluation” because it can relate to a potential cord issue.
The article also notes that stillbirth due to cord issues often occurs between 2 and 4am, and may relate to hormonal issues.
Okay, I know I previously represented that stillbirth rate found to be a little lower with women who drink versus women who do not, but I do not want to suggest that drinking is a good idea. This article looked into this exact issue:
It noted that drinking 1 or more drinks a day is associated with reduced birth weight and fetal growth restriction, heavy drinking is found to be associated with malformations, mental retardation, and behavioral and psychosocial problems in childhood and adolescence. The researchers asked mothers how many drinks they had a week, and mothers could answer <1, 1–2, 3–4, 5–9, 10–14, 15–19, 20–29, 30–39, and ≥40 drinks/week. Because there were so few women in the higher categories (thank goodness!) they grouped the women into four groups: <1, 1–2, 3–4, and ≥5 drinks/week. The vast majority of women (68%) were in the <1 group. 23% were in the 1-2 group, 7% were in the 3-4 group, and the remainder (2%) were in the higher groups. (For the groups of 15 drinks/week and above, it was less than 0.4% of the group). Of those groups, the stillbirth rate was 4.2/1,000 for the <1 drink per week group, 5.1 for the 1-2 drinks per week group, 5.6 for the 3-4 group, 10.6 for the 5-9 group (although there were not actually a thousand women in this group, so I extrapolated), and 32.5 for the 10-14 group (same). The sample sizes were so small for the higher drinking groups that there were no stillbirths in that group. (Which is not to say that drinking that much is okay, obviously.) The article also tracked infant deaths: 5/1,000 for the <1 drink per week group, 4.1 for the 1-2 group, 4.5 for the 3-4 group, and 6.4 for the 5-9 group (although there were not actually a thousand women in this group, so I extrapolated). There was only one infant death in the higher drinking groups (again, the sample sizes were small), representing a 62.5/1,000 infant death rate. So, the stillbirth rates were lowest in the <1 drink/week group, but still relatively low in the less than 4 drinks/week groups. The numbers went up dramatically in the 5+ drinks/week group. Infant death rates, on the other hand, were actually pretty steady until the highest drinking groups, but there were very few women in those groups.
The researchers calculated a stillbirth “risk ratio” for each group, and compared that to other “risky” things. <1 drink/wk = risk ratio of 1. 1-2 = risk ratio of 1.23. 3-4 = risk ratio of 1.35. ≥5 = risk ratio of 2.96. Smoking is still worse. 0 cigarettes/day = risk ratio 1. 1-9 = 1.51. ≥10 = 2.23. (The infant death risk ratio was also worse with smokers.) Caffeine intake had the lowest risk ratio for women who had 200-399mg/day, and the highest risk ratio for women above 400mg/day. (Strangely, for infant death it was the opposite.) For a maternal age of 25-29, the risk ratio was 1. <25 is .87 and ≥30 is 1.06. (Note that’s different than what I read above, which suggested that once chromosomal abnormalities were pulled out there was not an increased risk for stillbirth in older moms. And for infant death it was the opposite.) BMI risk ratio was 1 for 18.5-24. It was 1.47 for <18.5, 1.22 for 25-29, and 2.82 for ≥30. (Once again showing the risk of stillbirth increases with increasing maternal age. The results were similar for infant death.) Women who were single actually had lower risk of stillbirth than those who were married/cohabitating. (But for infant death the result was opposite.) Students had a lower stillbirth risk ratio than women who were employed, who had a lower rate than women who were not employed. (Also different than what I read above. Infant death risk was similar.) The more education mom had, the lower the risk of stillbirth (but, strangely, that did not hold for infant death). For parity, they only did 0 (first pregnancy to viability) or ≥1. Stillbirth risk (and infant death risk) was lower with ≥1. Preterm delivery was, unsurprisingly, a risk factor for stillbirth. (No preterm birth = risk ratio of 1, yes = 21.72. Risk was also higher for infant death.) Same for birth weight. (<2,500g [~5.5lbs] = 29.29 v. ≥2,500g = 1.) Risk was also higher for infant death.
The authors concluded that the risk of stillbirth increased with increasing alcohol categories, and women who drank ≥5 drinks / week had almost 3x the risk of women who drank <1 drink/week. The cause was mainly due to fetoplacental dysfunction. They noted previous studies had inconsistent results. The authors also suggested that underreporting of alcohol use was a risk. They also noted that their data did not allow them to distinguish between women who totally abstained and those who drank less than 1 drink a week. But they were not concerned about it, because “In a recent study, when we focused on low-to-moderate intake, we found that a very large group of women (5–44 percent) who reported being total abstainers on the questionnaire actually reported consuming small amounts of alcohol (>0 but <1 drink/week) in interviews or diaries, and vice versa”. In other words, women who report not drinking might actually drink a teeny bit.
Interesting.
Okay, so I’ve read a fair bit about stillbirth, risks, etc. What are my takeaways?
· Babies measuring less than the 10th % for weight are at a much, much higher risk for stillbirth.
· Don’t smoke, don’t drink (much), try not to be obese or too thin.
· Diabetes is a bitch. Preeclampsia is a bitch. Lupus and antiphospholipid syndrome? Also bitches. In general, mom’s health issues pose a risk to babies.
· Twin pregnancies are riskier.
· Women with bleeding are more likely to have a stillbirth.
· Boys are 10% more likely to be stillborn.
· The jury is still out on how much of an increased risk there is for increased maternal age, particularly when birth defects are not taken into account.
· Stillbirth risks are higher for first time moms and women who have a lot of kids.
· The 18-20 week ultrasound should include a review of the umbilical cord.
· After 28 weeks, go to the hospital if your fetus has the hiccups more than 4 times a day.
· Keep cool at the end of your pregnancy!
· Sleep on your left side, or at least try to. Avoid sleeping on your back.
Honestly, reading about all of the different causes / risk factors of stillbirth made me feel much better. I feel like my risk of stillbirth isn’t actually all that high, and I have some things I am going to do (or try to do) to make my risk even lower.
