Kathryn Gray
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The Peter Attia Drive · #410 ‒ The biology of pregnancy: physiologic adaptation…
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How Much Does Plasma Volume Rise in Pregnancy?
Plasma volume starts expanding immediately in pregnancy and is increased by 50% by 28 weeks. One panelist says the rise is pretty linear, really accelerates in the second part of the second trimester, and then levels off. Asked how much of the mother's plasma expansion occurs in the first trimester, one panelist places the start at the very beginning and the total increase at 50% by 28 weeks.
A co-host calls a 50% increase in plasma volume by 28 weeks remarkable. A co-host asks whether the rise comes with a fifty percent increase in oxygen-carrying capacity, and whether hemoglobin concentration expands to compensate. One panelist says a relative anemia forms due to the expansion. The larger
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Why Does Preeclampsia Raise Blood Pressure and Spill Protein?
Kathryn Gray says both the hypertension and the proteinuria of preeclampsia come from an angiogenic imbalance. She describes the classic model, and she notes it may not be true for everyone. The trouble starts early in pregnancy, when the placenta has to rebuild the mother's blood supply.
Placental trophoblasts should invade the maternal spiral arteries and let them become wider, lower-pressure vessels that supply the placenta with adequate blood flow. If the invasion is not adequate, the placenta develops some degree of hypoxia. The placenta then releases an anti-angiogenic factor into the maternal circulation. The factor soaks up VEGF, a growth factor that maintains endothelial cell funct
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Do Half of Gestational Diabetes Patients Get Type Two?
One panelist says 50% of patients who have gestational diabetes will develop type 2 diabetes. A co-host asked whether women who develop gestational diabetes also have a higher risk for type 2 diabetes and whether the history is predictive. The reply was yes.
A co-host asked about studies that would randomize women who develop gestational diabetes to one intervention versus another to delay or avoid type 2 diabetes, and said such a study would take a long time so the answer is almost assuredly no. One panelist says the recommendation is frequent follow-up for diabetes screening and advice on any lifestyle changes that would impact the risk of type 2 diabetes. A healthier diet, appropriate bo
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Can Four Centimeters of Dilation Last for Weeks?
Kathryn Gray says dilation by itself does not mean a woman is in labor. People can sit at three to four centimeters dilated for weeks and not be in labor. Other people come in four centimeters dilated, contracting painfully every three minutes, and they are definitely in labor.
The cervix is the lower part of the uterus inside the vagina, and clinicians monitor it for dilation. In early and mid-pregnancy, dilation is a sign of premature cervical dilation and can be preterm labor. At term, it is very common for the cervix to get thinner and softer, and it may start to dilate as the body gets ready. A digital check then shows whether somebody is in labor and how labor is progressing in the ho
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Why Did Pregnancy Amniocentesis Become Much Less Common?
One panelist says the number of invasive pregnancy procedures, including amniocentesis and chorionic villus sampling, has decreased. A primary driver is better screening for chromosomal disorders such as Down syndrome with cell-free DNA.
A tube of maternal blood contains fragments of placental DNA, and the sample screens the pregnancy for chromosomal conditions. The test is best for trisomies 21, 18, and 13, and for fetal sex. It is less good for other findings. Clinicians can run it as early as nine or ten weeks, and it is recommended to be offered to all pregnant patients.
Before cell-free DNA, a serum screen looked at three or four protein markers in maternal blood. When the protein lev
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Why Do Contractions Cause More Labor Pain Than the Head?
Contractions cause most labor pain. Delivery of the head forms only a thirty second part of labor while contractions continue for hours.
Most of labor is contractions. The delivery of the head is a thirty second part of the whole thing. Contractions go on for hours. A nurse described the pain of contractions to a husband who did not want an epidural by comparing the sensation to having balls slammed in a drawer again and again and again. The pain goes on for so long. Delivery of the head is very very painful. An epidural was used with all three labors. On the third one the medicine was more dilute and supposed to spread around better to give better coverage. There was no coverage right at t
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Why Does Missing One Feeding Make Lactation Not a Good Form of Birth Control?
Most women possess the physiologic capacity to produce breast milk. Breastfeeding requires a maternal and neonatal partnership. Complex hormonal interplay in the endocrine system drives milk production. A lactating woman has a harder time ovulating. Lactation was generally viewed as one method of birth control.
Missing one feeding makes lactation not a good form of birth control. A lactating woman will have very suppressed levels of estrogen and progesterone. If a woman skips any feeds then suppression of the cycle stops. Lactation only works as birth control when a mother maintains an uninterrupted feeding schedule. Women should not rely on lactation for birth control because one missed fe
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Why Does Early Water Breaking Bring Birth Within a Week?
Premature preterm rupture of the membranes at 28 weeks requires hospital admission. About half of patients deliver in the next seven days. The remaining patients stay in the hospital with ruptured membranes and receive monitoring all the way up until 34 weeks if everything looks reassuring. Antibiotics given at presentation help prolong latency without preventing all infections.
When water breaks at 28 weeks doctors call the condition premature preterm rupture of the membranes. Patients come into the hospital. About half of patients deliver in the next seven days after spontaneous labor begins. Other patients sit with membranes ruptured and low amniotic fluid but continue to make the fluid
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Why Does a Classical C-section Carry a Ten Percent Risk of Uterine Rupture During Labor?
A uterine rupture is an emergency and a surgical emergency. Surgery on the uterus from big fibroid removal or a prior classical C-section cuts through the musculature of the uterus. The type of incision from a classical C-section is much more likely to rupture during labor with a risk of like ten percent. Ten percent risk is too high so the group should not labor.
A low transverse C-section is preferred in term patients where it is almost always possible. Delivery of a preterm baby is one of the most common reasons for a classical C-section. The uterus has not expanded enough and the lower uterine segment is not developed. An incision in the lower part of the uterine segment may not safely
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Why Did Cesarean Births Triple in America?
C-section rates in the United States increased dramatically from ten percent to thirty percent over the last fifty years. Different drivers explain the three X increase. Pregnancies are higher risk than they used to be. An increase in maternal obesity has raised the number of larger fetuses or cases where labor does not progress normally. The switch to continuous fetal monitoring during the active phase of labor in most hospitals leads to more C-sections when the tracing is not reassuring.
Once a patient has one C-section, the patient is more likely to have another one. Multiple C-sections increase the risk for abnormal placentation in the next pregnancy. The specific issue is placenta accr
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How Long Does Preeclampsia Blood Pressure Last After Birth?
Hypertension from preeclampsia follows a different resolution timeline than gestational diabetes does after delivery. A woman can be off insulin by the time she goes home when gestational diabetes resolves. Hypertension from preeclampsia does not resolve in the same way. Some women will have hypertension resolve very quickly after delivery. Many women need antihypertensive medications for several weeks after delivery because hypertension can take six to twelve weeks to come back to more of a baseline.
There are other women who will have persistent hypertension after delivery and never quite resolve the hypertension. Lots of women will come back and develop hypertension within the next five
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Why Does Every Pregnant Woman Become Insulin Resistant?
It is not an oversimplification to say that every woman has to become insulin resistant during pregnancy because the adaptive response preferentially directs nutrients to the fetus. Genetic factors probably amplify the response in some women. Environmental factors would also amplify the response in some women. The environmental factors could be stress, sleep, nutrition, et cetera. The framework is a great one for the point.
Interestingly, gestational diabetes does not always recur in every pregnancy. The process is not fully understood. Like almost everything in medicine, if a woman has had gestational diabetes before, the woman is more likely to have gestational diabetes again. Not everyon
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Why Is Insulin the First Medicine for Gestational Diabetes?
First line treatment for gestational diabetes consists of dietary modifications along with nutrition consultation and glucose monitoring in women who presented metabolically healthy prior to pregnancy. Targets include fasting values under ninety five and one hour postprandial values under one forty. Monitoring continues until more than half the values stay below targets.
The short interval between diagnosis at twenty eight weeks and delivery limits lifestyle intervention to roughly two weeks. Elevated values in the first week lead directly to medication rather than extended attempts at control through diet alone. Insulin functions as first line medication during pregnancy due to insufficien
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Why Take Prenatal Vitamins Before You Plan a Pregnancy?
Folic acid must be at adequate levels prior to conception. Good evidence shows that folic acid deficiency increases the risk of having a neural tube defect in the baby. By the time a woman recognizes the pregnancy, it is already too late to bring up folic acid levels if a deficiency had been present. Folic acid is one of the most essential things early on.
Fifty percent of pregnancies are unplanned. Prenatal vitamins should be recommended to all women of childbearing age. A well-balanced diet works because much of the food supply is supplemented with B vitamins and folic acid along with other nutrients that women need to replenish during pregnancy.
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How Did Genetics Find the Cause of Hyperemesis Gravidarum?
Genetics provided great insight into hyperemesis gravidarum by flagging the GDF15 gene as really important in driving the condition. The GDF15 gene is now a developing target for therapeutics and the discovery suggests prior understanding of causes for hyperemesis gravidarum was not correct.
For a long time people thought HCG caused nausea and vomiting of pregnancy. Researchers studied folks who had hyperemesis gravidarum and found a signal at the GDF15 gene. Women who experience hyperemesis gravidarum in a first pregnancy often experience hyperemesis gravidarum in all pregnancies. Less than one percent of folks require hospitalization for hyperemesis gravidarum with IV hydration and even I