Making Sense of Pregnancy: What Experts Want you To Know About Your Body

 IWhat if we could actually watch the conversation between a fetus and its mother? Not metaphorically—the individual cells, where they are, what genes they're expressing, and how that conversation changes over the course of pregnancy. That's essentially what Dr. Fisher and her team have done in their creation of an atlas of the maternal fetal interface, that irregular boundary formed between mother and fetus key to all human life on the planet. 

This week I'll continue my conversation with Dr. Fisher, focused on how new knowledge of this interface can be used to understand and potentially affect serious complications in pregnancy, and what the future may hold for intervening in a pregnancy complication while it's unfolding.

 I don't think I can oversell today's episode. 

We'll discuss the most detailed atlas of the maternal fetal interface-- that meeting and intermingling of maternal and fetal cells that sets the stage for placental creation and development. The sheer awe of the accomplishment of the research we will talk about today may be something that draws you in to this conversation. 

This work represents the cutting edge of pregnancy research, and it shows how unbelievably complicated it is for a fetus to make a placenta and for that placenta to integrate itself into the mother's body.

 Not only does this work give an incredibly detailed picture of the exact cells in the interface, the spatial location of those cells, accounting for which specific cell sets are near each other and what they likely communicate to each other, and the genes that make that communication possible; it also gives a sense of how the interface changes over time by looking at this interface from weeks five to 39. 

It's work on this level that may hold the keys to developing a way to treat many endometrial spectrum disorders like preeclampsia, placental accreta, and even things like preterm birth.

 Since women have been having babies, they've experienced miscarriage.

For nearly as long, we have not had a useful way to address miscarriage. 

Often doctors shrug at your first miscarriage and say it's a normal part of pregnancy. And if it arises because of aneuploidy, the fertilized egg is the wrong number of chromosomes--at this point, there's not much we can do about it. 

But there are alternative routes to miscarriage. 

Today's guest is working to better understand other mechanisms at play in miscarriage. In particular, he's focused on what happens in the endometrial lining to make the uterus into a hospitable place for pregnancy. This is a re-editing version of two episodes that I published a year ago about this research. 

In the next couple weeks, I'm talking to more people who are studying the endometrial lining, so it is a good time to re-acquaint ourselves with the current cutting edge of this research. 

The paper we reference is : Stalling of the endometrial decidual reaction determines the recurrence risk of miscarriage:  https://www.science.org/doi/10.1126/sciadv.adv1988

 Embryos speak multiple languages. 

They can communicate through chemistry, which has been known for a long time, and as today's guest will describe, they can also detect physical features of their environment and alter their biology in response--which is to say they are mechanosensitive. They can generate forces that deform their surroundings, and they can respond to the force cues around them. We'll talk more today about the experiments that allowed us all to witness this ability in the viral video that captured implantation of a human embryo into a 3D matrix for the first time. 

If you want to see the video,  https://ibecbarcelona.eu/human-embryo-implantation-recorded-in-real-time-for-the-first-time/

Also, in the paper, available here: https://www.science.org/doi/10.1126/sciadv.adr5199 there is a supplmentary section that has more videos that show the 3D displacement, check out adr5199!

 If you're on the internet even a little bit, you likely saw the viral video first released last August That showed for the first time what a human embryo implanting into a 3D matrix looked like. 

The video comes from work trying to explore what the embryo is actually doing during implantation. Despite how critical this process is, implantation, required for any and every pregnancy, is one of those black box topics. 

Both the details of exactly how the blastocyst attaches to the uterine lining and how it embeds itself into the lining have been virtual mysteries. We do have animal models. We've seen parts of this process in a Petri dish. We've never seen it in 3D before, until now. 

Today, I'll talk to the first author of the paper from which the viral video sprung. The group of scientists that studied this question examine The many things an embryo can do unprompted by an effective uterine lining, and it is mind-blowing.

Traction force and mechanosensitivity mediate
species-specific implantation patterns in human and
mouse embryos: https://www.science.org/doi/10.1126/sciadv.adr5199

 Your menstrual cycle requires the coordination of a number of different systems in the body. We've all heard of the hypothalamic pituitary ovarian axis, AKA the HPO axis. But the system is embedded in and reactive to many other systems in the body, including the uterus, and particularly the uterine lining, the immune system, metabolic and energy sensing networks, stress axis, the thyroid adrenal axes, circadian timing systems, autonomic nervous system, liver, bone, vascular system, and the gut. 

Ovarian estrogen and progesterone act as whole body signals. Using menstrual cycle characteristics like cycle length, like variability of cycle length, like the heaviness or lightness of bleeding as signals of vitality or distress, may be an opportunity to better understand both our own fertility and our own overall health. 

We'll get into some of the details about what is being done now and what the future looks like for using the menstrual cycle as a vital sign. 

 The menstrual cycle plays an enormous part in the lives of half the population of the world. People tend to focus on it as a conduit to pregnancy, and it is. But through the hormonal fluctuations that drive this cycle, it affects many other aspects of health. A better understanding of what a, quote, "normal cycle" looks like and how to understand your own cycle can impact other facets of your health because most cells in a woman's body have receptors for estrogen and progesterone. Given the importance of this process, doctors and researchers, like the one I'll talk to today, are thinking about the menstrual cycle as a vital sign, like temperature or heart rate or blood pressure. It's a way to check in on many other physiological processes in your body, not only in adolescence, but through menopause.

The Menstrual Cycle as a Vital Sign: A Comprehensive review: https://pmc.ncbi.nlm.nih.gov/articles/PMC11790291/

 In the olden days, and in some circle even today, women measure(d) something called basal body temperature, which is a core temperature that can be used to track ovulation, by measuring their temperature right when they wake up. It's the first thing you do --with a special thermometer that measured to at least one 10th of a degree, and to record it on a chart, maybe on your phone, maybe on actual paper to identify a subtle temperature shift. 

But those were the horse and buggy days of biohacking for fertility. Now we can wear a ring that provides a continuous readout of your temperature and sends it to an app on your phone. And not only can it tell you if you are ovulating. It may be able to tell you if you're pregnant BEFORE the tests you can get at the pharmacy.

Today we talked to Dr. Benjamin Smar PhD, who has used sensor data to uncover some of the dynamics of your body in pregnancy. 

 Historically, one of the reasons for excluding women from clinical trials has been the idea that women's menstrual cycles have made their data too variable to study.

 Wearable tech can and is having an impact on this specific issue, as researchers use data from watches and rings to not only track a cycle, but beyond that, to track many other aspects of physiology at the same time. 

In fact researchers are now moving beyond that simple goal to try to make sense of these physiological changes in the context of our cycles. Today, I finish my conversation with Dr. Sarah Johnson, who's looking at data from wearables to understand both normal cycles and those impacted by various forms of birth control. 

The menstrual cycle through the lens of a wearable device: insights into physiology, sleep and cycle variability : https://www.nature.com/articles/s41746-026-02799-9

 Wearables are everywhere, and they're tracking all manner of physiological signals continuously, including our heart rate, temperature, respiration rate, and other features while we go about our daily lives. 

Do these devices actually measure what they say they measure? Are they reliable?And if they are, can this information be linked to the menstrual cycle to better understand normal and abnormal cycles and symptoms?

Today, I talk with a researcher trying to wring meaning out of the data generated by these wearables to better understand women's health with specific interest in how changes in things like temperature, heart rate variability, respiration rate may offer clues about what's happening in our menstrual cycle, both when we take various forms of contraception and when we don't.

In this episode we talk about:
Decoding Menstrual Health Across the Lifespan: A Scoping Review of Digital Health Tools (2026): https://www.nature.com/articles/s44294-026-00146-7

If you want more details about the influence of copper IUDs on the tissue of the uterine lining, see: Effects of Copper Containing Intrauterine Devices on the Endometrium (2021): https://mednexus.org/doi/10.4103/2096-2924.309791