Smash Notes
#410 ‒ The biology of pregnancy: physiologic adaptation, gestational diabetes, preeclampsia, childbirth, and long-term maternal health | Kathryn Gray, M.D., Ph.D.
View the Show Notes Page for This Episode Become a Member to Receive Exclusive Content Sign Up to Receive Peter's Weekly Newsletter In this episode, Peter sits down with Dr. Kathryn (Katie) Gray, a physician-scientist, high-risk obstetrician, and maternal-fetal medicine specialist at the University of Washington School of Medicine. Katie begins by…
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Notes
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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 IV nutrition. The biggest risk of hyperemesis gravidarum is dehydration and lack of nutrition for the mother since the fetus takes what the fetus needs from the mother.
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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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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 insufficient data on efficacy and safety for many other agents. Metformin qualifies as fairly safe in pregnancy and potentially helpful. Insulin delivers the most effectiveness along with strong safety data plus the best influence on improving neonatal outcomes.
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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 everyone gets gestational diabetes again.
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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 to ten years as well. Recovery timelines vary significantly among different women who experience preeclampsia during pregnancy.
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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 accreta spectrum where the placenta invades abnormally into the uterus during pregnancy and the placenta does not come out after the baby.
A lot of focus exists on trying to decrease the number or avoid any further increase.
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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 deliver the preterm baby. A classical C-section is also chosen for surgical complexity when patients have had multiple C-sections and scar tissue prevents access.
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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 and leak the fluid. Infection counts as a high concern. Rapid labor progression occurs often. Cord prolapse becomes a risk if the baby is not head down and creates an emergency. Antibiotics are administered at the time of presentation to prolong latency and pregnancy duration but no further antibiotics follow the initial dose.
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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 feeding allows the menstrual cycle to resume.
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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 the perineum. Everything could be felt when the head came out.