If you ask any pregnant woman if she felt differently before she conceived and after giving birth, she will concur immediately. It’s well known that pregnancy and delivery dramatically affect virtually all systems of the woman’s body, but until now, these changes have, surprisingly, not been systematically analyzed over time in a large human population.
Now, researchers at the Weizmann Institute of Science in Rehovot have accomplished this with 76 lab tests based on a cross-sectional analysis of 44 million measurements from over 300,000 pregnancies that included about half of the pregnancies in Israel between the years 2003 and 2020.
The data, obtained using the large database of Clalit Health Services (the country’s largest health fund, covering 55% of the Israeli population), provide a comprehensive dynamic portrait of pregnancy, the first of its kind – a comprehensive picture of physiological changes in the mother’s body during and after pregnancy.
Prof. Uri Alon and his team in the institute’s department of molecular cell biology have just published their study in the journal Science Advances under the title “Pregnancy and postpartum dynamics revealed by millions of lab tests.”
The research team, led by Dr. Alon Bar and Ron Moran, in collaboration with Dr. Yoel Toledano from the maternal fetal medicine division at the Helen Schneider Hospital for Women at the Rabin Medical Center in Petah Tikva, analyzed weekly changes in each of the 76 parameters from 20 weeks before conception to 80 weeks after delivery.
The multidisciplinary team consists of physicists, biologists, computer scientists, and MDs working together to form the basic equations of hormone circuits, antibiotics, autoimmunity, cancer, mood disorders, and age-related diseases.
Alon told The Jerusalem Post that he knows of no such study conducted abroad, and foreign researchers expressed much interest.
Birthrates down
“The birthrate is way down in Europe and places like Japan. Over the course of three years, we examined data on Israeli Jews and Arabs, ultra-Orthodox (haredi) and Bedouin women who give birth to large children. It usually takes a year for women to return to their base condition. Some need more medical supervision than others. I’m not a gynecologist, but there are some countries with very short maternity leaves, and for some, the women return too soon.”
The extensive results highlight the massive physiological load of childbirth. In about half the tests, the values returned to baseline only three months to a year after the delivery. Alongside healthy pregnancies, the researchers also tracked pregnancy complications such as gestational diabetes, pre-eclampsia, and postpartum bleeding.
The precision of the data revealed effects of preconception supplements, overshoots after delivery, and intricate temporal responses to changes in blood volume and kidney filtration rate. Pregnancy complications – gestational diabetes, pre-eclampsia and postpartum hemorrhage – showed distinct dynamical changes.
During pregnancy, the mother’s cardiovascular, respiratory, renal, gastrointestinal, skeletal, metabolic, endocrine, and immune systems are all affected by fetal demand and massive endocrine secretion by the placenta.
Elevated demand for oxygen and nutrients causes an increase in cardiac output and up to 50% growth in blood volume; the kidneys increase the glomerular filtration rate by 50%, leading to increased urine production.
The immune system is modulated to prevent rejection of the fetus, and coagulation and red blood cells show marked changes, while metabolism shifts to increased insulin resistance and lipid production to supply energy for fetal growth.
Delivery marks a profound change, as the fetus and placenta leave the body and abruptly cease their metabolic and endocrine effects. The mother undergoes a series of adaptations in which various physiological systems recover with different timescales – from hours to months.
During pregnancy and after delivery post an increased risk of complications including gestational diabetes, postpartum hemorrhage, anemia, depression, and eclampsia (a serious blood pressure condition that develops during pregnancy that leads to high blood pressure and high levels of protein in the urine; it usually develops after the 20th week of pregnancy).
Understanding healthy physiology and pathology is essential for both advancing basic science and as a baseline for treatment. This understanding of the physiological changes during pregnancy and postpartum requires precise temporal data on numerous physiological parameters. However, existing studies have a limited number of participants, consider only a few parameters, and have been tested only about three times during the pregnancy.
“Knowledge is even more sparse in the postpartum period in which a single time point is usually measured,” the team wrote.
“The precision of the dataset allows detection of intricate dynamical changes, including the impact of preconception supplements, and the deviations from healthy pregnancy in pre-eclampsia, gestational diabetes, and postpartum hemorrhage,” they wrote.
“This study thus provides a resource for understanding pregnancy and the postpartum period and demonstrates how it may be used to understand mechanisms in systems physiology, and it greatly expands our knowledge of the postpartum period.