“ Women's health is understudied. Pregnancy places a significant burden on the body, and we wondered how physiology adapts to this burden." explains Uri Alon, who led new work of unprecedented magnitude on pregnancy and published in the journal Science AdvancesData from more than 300,000 women in Israel from 22 weeks before pregnancy to 80 weeks after delivery allowed researchers to accumulate comprehensive statistics on the course of a pregnancy and its possible complications. Our data cover half of the Israeli population over the age of 20, all medical records combined, on the 76 most common laboratory tests" explains Uri Alon.
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“ Human gestation is a little-explored area of research, partly because it is difficult to study for both ethical and practical reasons.", comments Michelle Oyen, a biomedical engineering expert who was not involved in this work, in a commentary published in the same journal. During pregnancy, the needs of the fetus profoundly modify maternal physiology at the level of the cardiovascular, respiratory, renal, gastrointestinal, skeletal, metabolic, endocrine and immune systems, the researchers list. Knowledge that, rather reassuringly, the majority of the study results confirm. " The mother's physiology changes in every possible system. More blood lipids, blood volume increases by 50%, renal filtration rate increases, etc." illustrates Uri Alon.
Half of the indicators take at least ten weeks to return to normal after delivery
But some surprises emerge. After delivery, it takes a year for many tests to return to baseline, not six weeks as was commonly thought.", reveals Uri Alon. Childbirth marks a profound change because the fetus and placenta abruptly cease their metabolic and endocrine effects.
While 47% of the indicators return to normal after the first month postpartum and 12% within two weeks, 41% of the measured values take ten weeks after birth to return to their baseline state. Some take up to a year, or even never return to their original state. Liver functions thus take six months to recover given the levels of transaminase enzymes ASAT and ALAT, both produced by the liver. The amount of alkaline phosphatase (ALP), indicative of liver and bone health, as well as cholesterol levels, on the other hand, take a year to stabilize. These differences could result from postpartum behavioral changes (like breastfeeding and the hormones that underlie it, editor's note) or lasting physiological effects of pregnancy (like weight gain and therefore BMI, editor's note),” the researchers say.
Rates that remain abnormal even a year and a half after childbirth
Finally, some values have still not returned to their original levels after 80 weeks (about a year and a half). These include complement-reactive protein (CRP), a marker of inflammation, which remains elevated. Similarly, anemia markers such as iron and hemoglobin (TCMH) levels, as well as thyroid-stimulating hormone (TSH) levels, remain lower than before pregnancy.
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The risk of three common pregnancy complications begins even before conception
Examining the dynamics of three of the most common pregnancy complications—gestational diabetes, preeclampsia, and postpartum hemorrhage—shows roots that predate pregnancy itself. The researchers reveal that for all three complications, some of the significant changes are observed before conception or after delivery rather than during gestation. Women with risk factors such as obesity are more likely to have complications and also have abnormal results before pregnancy.", points out Uri Alon in particular.
This is particularly the case with gestational diabetes, where 17 of the 20 parameters examined already differ from the norm even before conception, including 12 which only diverge during this preconception period. This is interesting given that tests to diagnose conditions such as gestational diabetes and pre-eclampsia are performed during gestation", scientists point out.
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“ A fundamental question arises regarding pregnancy complications: did the pregnancy cause the problem, or did it simply subject the body to enough stress to reveal an underlying pathology that would have eventually manifested itself otherwise?" asks Michelle Oyen. A question she considers particularly important in the case of cardiovascular diseases, which are the leading cause of death among women worldwide and whose risk increases during the decades following childbirth in women who suffer cardiovascular complications during pregnancy.
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