The Lancet: Weight Gain Increases Stillbirth Rate
Maternal weight gain before the birth of a second child is associated with an increased risk of stillbirth and infant death within the first year of life. The study was interviewed by Medscape and was published recently in THE LANCET.
In 15% of women, body mass index (BMI) gain between the two births was between 2 and 4 (weight gain of 6 to 11 kg), and in 6% of women, BMI gain was greater than 4. This weight gain, without counting first birth weight gain, resulted in a 30% to 50% increased risk of stillbirth. For normal weight women, the same weight gain leads to a 27% to 60% increase in the risk of infant mortality in the first trimester. In contrast, for overweight women, studies have found that a reduction in BMI by 2 (6 kg) reduces the risk of infant mortality by 50%.
Overweight and obesity are becoming a worldwide problem because of the association with pregnancy complications and may have a predictive effect on neonatal mortality. Weight gain between pregnancies is associated with preeclampsia, gestational diabetes, preterm delivery and stillbirth. This association is more pronounced in normal weight women than in overweight or obese women.
Professors Cnattingius and Villamor have therefore investigated the effect of weight gain between pregnancies on stillbirth and neonatal mortality in the second trimester. Cord winding is very common and its occurrence is associated with excessive cord length, small fetus, excessive amniotic fluid and frequent fetal movements.
Effect of cord entanglement on perinatal outcome
A loosely wrapped umbilical cord has little effect on the fetus, while a tightly wrapped cord with multiple loops may affect the fetal blood supply and risk fetal heart changes, perinatal hypoxia, asphyxia and even death.
Based on this, Narang et al. conducted a study on vaginal delivery of fetuses with umbilical cord entanglement.
However, Prof. Gursoy et al. presented their own view on this study, which was published in the Archives of Gynecology and Obstetrics.
They stated that the study of the effect of cord circumference on maternal and infant morbidity is very important for obstetricians. In this regard, they are grateful to Narang et al. for their attention to this common but unresolved topic.
Most of the studies on this issue have reported conflicting results, with the majority emphasizing that cord wrapping has no effect on perinatal outcomes. Some researchers, however, have suggested that cord wrapping can lead to hypoxia or even cerebral palsy.
Professor Gursoy et al. concluded that the study appeared to have a biased design for patient selection, which would likely lead to some unintended consequences.
The study reported that they selected 2000 patients who were eligible for the study (one or more weeks of umbilical cord winding for vaginal delivery).
They claimed that cord winding had a significant effect on the pH of the umbilical artery, including pH and lactate values.
The pathological biochemical fluctuations in the non-cord-wrapped group may be due to pathological dissection of the umbilical artery when the pH of the umbilical artery is 7, which is an important parameter affecting long-term prognosis.
Cord winding and cesarean delivery
The trial did not mention patients who were eligible for the study and delivered by cesarean section.
Cesarean delivery due to cord winding is reported in about 11.1-35% of patients, and in China cord winding is one of the four main indications for cesarean delivery.
According to these reports, although cord winding is not an indication for cesarean delivery per se, the decrease in fetal heart rate due to cord winding, for example, can prompt a patient to undergo a cesarean delivery.
Although labor is a complex process, the researchers ruled out almost all factors that could affect delivery.
At this point, the patient was left with only one possible factor that would require a cesarean delivery – the cord wrapping around the neck and the number of weeks it was wrapped around the neck.
This is why they suggest that the authors do some studies on this, so that it is possible to claim that cord winding is not an important factor affecting the course of labor.
Cord winding and neonatal blood pH
In conclusion, the retrospective studies that reported that cord winding affects to some extent the acid-base status of the umbilical artery, while supporting the results of this study, it is not known whether these factors have a long-term effect on the relevant aspects. This ‘unknown’ requires us to be more cautious when drawing conclusions on this issue.
Narang et al. have since responded, thanking Prof. Gursoy et al. for their in-depth study of the experiment as well as their evaluation. However, there is a small correction to their assessment of “pathological fluctuations in pH and lactate values in the non-cord-wound group in the study”.
Their study found that the blood pH of neonates in the cord-wrapped group was slightly lower than in the non-cord-wrapped group; however, the pathologically significant pH fluctuations in neonates not in these two groups often suggest the presence of cord blood disruption due to cord-wrapping, resulting in biochemical disturbances.
However, in those neonates who were able to tolerate vaginal delivery, there was only a slight decrease in pH due to the placenta’s ability to rapidly compensate for ischemia, and even fewer cases reflected pathological pH alterations.
In contrast, newborns in the cord-wrapped group, who are unable to compensate for umbilical artery ischemia, suffer intrauterine distress and are forced to undergo a second cesarean delivery. They were not able to determine whether this condition exists in fetuses of patients delivered by cesarean section, and therefore they were not included in the study.
There are several reasons for considering the exclusion of cases in which the umbilical cord was wrapped around the neck via cesarean delivery.
First, the experiment initially they wanted to assess only the effect of vaginal delivery on the prognosis of cord-wound children.
Second, to eliminate errors, since the most common cause of emergency cesarean delivery, intrauterine distress, may be caused by various reasons (e.g., contamination of amniotic fluid, labor arrest, lack of contractions, arrest of the second stage of labor, cephalopelvic disproportion, etc.).
If these conditions are also present, the umbilical cord encirclement becomes a cause of intrauterine distress and an indication for cesarean delivery.
Since they only observed vaginal deliveries, they do not have data on cases of cesarean delivery due to cord winding.
In this regard, the group is conducting further studies to better elucidate this aspect of the problem.
The researchers conducted a cohort study of birth registration data from the Swedish Medical Center between 1992 and 2012, including 456,711 women who delivered their first and second child during this period, to assess the effect of increased maternal BMI at first and second births on stillbirth (28 weeks and beyond) and infant mortality (up to 1 year).
Of these participants, 13.1% had a BMI decrease ≤ 1 between births, 45.9% had no change in weight (BMI change between -1 and < 1), and 41.1% had a BMI increase ≥ 1.
The risk of stillbirth and neonatal death was 1.55 times higher in women with a BMI increase >4 compared to women with no significant weight change between births. The risk of stillbirth increases linearly with BMI, with women with a BMI increase >4 having a 50% higher risk of stillbirth than women whose weight remains constant.
Normal first birth weight (<25 kg/O) and weight gain between births increases second birth infant mortality, with high infant mortality for BMI increases of 2 to 4 or 4.
Although weight gain leads to a linear increase in infant mortality, it is only at BMI gains ≥4 that mortality increases in young children after 1 year of age.
It is important to note that for women who were overweight at their first birth, weight gain between births had no effect on infant mortality. In addition, for overweight women (BMI >25 kg/O), a reduction in maternal BMI of more than 2 significantly reduced infant mortality, but for women of normal weight, the same weight loss increased the risk of infant mortality.
In these cohort studies, there was sufficient evidence of an association between weight gain and stillbirth between the two births, both in normal weight women and in overweight women. The studies also found that weight gain between pregnancies also increased the risk of subsequent stillbirths.
The studies suggest that normal weight women should control their weight gain before pregnancy and that overweight women should lose weight.