Benefits of a healthy lifestyle during pregnancy – health metrics before and during pregnancy and postpartum

Objective

Pregnancy is a transformative journey, bringing remarkable changes to a woman’s body as it nurtures new life. Hormonal shifts, increased blood volume, and adjustments in heart rate and sleep patterns are all part of this process. Our study conducted using the IVY® wrist tracker reveals the importance of a healthy lifestyle during pregnancy, showcasing how daily activity impacts health metrics like sleep duration and cardiac coherence. Discover how making informed choices can enhance your pregnancy experience and the well-being of both mother and baby. Dive into the full findings to empower your pregnancy journey with knowledge and insight.

Introduction

Pregnancy is a beautiful yet challenging period for a woman’s body and soul. Under the influence of hormones released by the glands of the pregnant woman and the developing placenta, the woman’s body adapts so that the fetus can develop and grow properly and prepare for later breastfeeding.

These changes, such as increased blood volume, physiological anemia, an increase in heart rate, cardiac output, respiratory rate, and a decrease in peripheral vessel resistance and blood pressure, are all in service of the growing fetus. It’s a reminder of the deep connection between the mother and the developing life. However, adapting the woman’s body to pregnancy is more successful if the woman maintains a healthy lifestyle during pregnancy, including enough sleep, rest, and at least 150 minutes per week of moderate activity (1).

Your choices matter and can make a significant difference in your pregnancy journey. A healthy lifestyle during pregnancy significantly impacts pregnancy health and maternal well-being through informed lifestyle choices.

What did we investigate?

At Bellabeat, we conducted a comprehensive investigation into the health metrics that pregnant women track during pregnancy with the wrist-worn tracking device IVY®. We studied how these metrics change before and during pregnancy and postpartum in a free-living setting, such as the number of daily steps, duration of sleep and deep sleep, resting heart rate and respiratory rate, and cardiac coherence. Our study also thoroughly explores the association between health metrics and physical activity, using the number of steps per day as an indicator, and well-being, using cardiac coherence as an indicator.

How did we perform the investigation?

For the purpose of investigation under the GDPR and CCPA, we generated a de-identified aggregated data set from the Bellabeat database, including 80 pregnant women who delivered at term. The data included number of steps per day, sleep duration (minutes), deep sleep duration (minutes), heart (beats/minute) and respiratory rate (breaths/minute) measured during sleep, and cardiac coherence by week 12 weeks before conception, 41 weeks during pregnancy, and 12 weeks after delivery. Resting heart and respiratory rate and cardiac coherence were measured during sleep. Cardiac coherence was calculated from the time interval between successive heartbeats divided by the mean time of the interval during one respiratory cycle. (2) Cardiac or physiological coherence is a crucial measure of the stability and harmony in the oscillatory outputs of the individual’s physiologic regulatory systems during any period. (3) It is reflected in an ordered sine wavelike heart rate pattern. This pattern is a visual representation and a key indicator of heart rate variability, a variation of heartbeat-to-beat interval mediated by the vagus nerve. Cardiac coherence is an interaction between respiratory rate, heart rate, and blood pressure oscillations and the end output of synchronization between various brain waves and the cardiac cycle. (4) The information in the heart’s inter-beat intervals is communicated across multiple systems and plays a vital role in synchronizing the bodily system. (4)

The wrist-worn tracking device IVY® is based on reflected-type green light photoplethysmography (green light PPG) to detect blood volume changes in peripheral tissue and measure heart and respiratory rate and cardiac coherence. The wrist-worn tracking device also incorporates a motion detection sensor MEMS-3 accelerometer (STMicroelectronics International NV) for step counting and sleep detection. The device has wireless connectivity with a frequency range from 2.400 to 2.483 GHz, Over-the-air update (OTA update), and real-time analysis. Data is processed using software licensed by CSEM. All measures are presented to users in the Bellabeat application on iOS 11.0 and Android 6.0 and later with the firmware version TBD, e.g., HR-1.210607448 (format HR-1.YYMMDDbuild_number).

Continuous variables in the investigation were presented as mean ± standard deviation (SD) by week 12 weeks before conception, 41 weeks during pregnancy, and 12 weeks after delivery. The strength and direction of the relationship between two continuous variables was calculated by Pearson’s correlation coefficient. A p-value < 0.05 was considered significant for correlation.

What did we find?

The mean number of daily steps, a testament to the resilience of pregnant women’s bodies, showed a pattern of decrease and increase. It decreased in the first trimester from approximately 7500 to 6000 steps per day, increased again in the second trimester to approximately 7000 steps per day, and then decreased again in the third trimester to less than 5000. After delivery, pregnant women demonstrated their resilience by becoming more active again, with a weekly increase to 8000 steps per day (Figure 1).

In the first trimester, the mean duration of overall sleep, a testament to the adaptability of the body, increased from approximately 450 to 460 minutes and decreased to approximately 350 minutes in the third trimester until delivery. The mean duration of sleep remained lower throughout the postpartum period, reaching no more than 400 minutes (Figure 2).

The mean deep sleep duration, a sign of the body’s stability, remained relatively stable at approximately 170 minutes until the 24th week of pregnancy when it slightly increased to approximately 185 minutes. After that time, it decreased just before delivery to approximately 165 minutes. In the postpartum period, the mean deep sleep duration gradually increased to approximately 195 minutes (Figure 3).

During pregnancy, there was a significant increase in the mean resting heart rate during sleep. It sharply increased after conception from approximately 69 to 73 beats per minute. After a slight decrease at the end of the first trimester, it steadily increased until the 32nd week of pregnancy, when it began to decrease until delivery. Immediately after, the heart rate decreased to approximately 64 beats per minute, and remained stable throughout the postpartum period (Figure 4).

The mean resting respiratory rate during sleep slightly increased after conception from approximately 15.5 to 16 breaths per minute, stayed stable until 16 weeks of pregnancy, and then slowly decreased until delivery to pre-pregnancy rate. After delivery, the mean resting respiratory rate remained stable at approximately 15.1 breaths per minute (Figure 5).

After a short decline of cardiac coherence, a testament to the body’s well-being, after conception from 6.8 to 6.4, it stayed unchanged from before pregnancy until the end of the first trimester, when it started to decline and reached the lowest value of 5.4 at the 28th week of pregnancy. After that period, cardiac coherence increased until delivery to approximately 6.6. A sharp increase followed after delivery to approximately 7.2 and stayed relatively stable throughout the postpartum period (Figure 6).

Analysis of the correlations between individual health metrics showed interesting results. The more steps pregnant women took per day, the longer they slept. As a result, they had a lower resting heart rate and greater cardiac coherence. A lower heart rate increases respiratory rate, increasing cardiac coherence. In contrast to sleep duration, the length of deep sleep decreased cardiac coherence both directly and indirectly by increasing the resting heart rate (Figure 7 and 8).

Are our findings comparable with other investigations?

Our measurements of health metrics with the IVY® wrist-worn tracker, such as resting heart rate, respiratory rate, and sleep, are comparable to those recorded by the iPhone and Apple Watch by Mishra et al. (5) on the American population of pregnant women. The difference is noticeable in the number of steps per day. In the study by Mishra et al., the number of steps per day fell in the first trimester and slowly decreased until delivery. Heart rate variability was reduced by approximately 25%. Pregnant women who used IVY® with the Bellabeat application also took fewer steps per day in the first trimester than before pregnancy. Still, after this period, they started walking again until the 28th week of pregnancy, when the number of steps decreased until delivery. Cardiac coherence, which reflects heart rate variability, decreased but by less than in the study by Mishra et al. (5), by approximately 21.5%. The renewed increase in the number of steps taken by IVY® users and a smaller decline in cardiac coherence than in iPhone and Apple Watch users can be explained by the simultaneous use of the Bellabeat application in our users. Bellabeat application, with its coaching program, encourages a healthy lifestyle with moderate activity during pregnancy. A decrease in heart rate variability indices in the second trimester was also measured in the study by Saharddi et al. (6) using a customized, remote, IoT-based monitoring system in a free-living context. Our findings, which highlight the importance of promoting a more active lifestyle during pregnancy, provide valuable insights for healthcare professionals, researchers, and pregnant women interested in health tracking. By analyzing correlations between our health measures, we found that the number of steps per day increases sleep time, reducing resting heart rate and rising cardiac coherence.

What do we learn from the investigation?

The IVY® wrist-worn tracker, with its ability to accurately record changes in health metrics, provides a reliable tool for monitoring pregnancy health. However, it’s the Bellabeat application that truly empowers pregnant women, effectively encouraging them to engage in moderate activity. This increased activity, leading to a higher number of steps per day, not only boosts sleep time but also mitigates the drop in cardiac coherence by the end of the second trimester. However, a larger cohort of women who will use IVY® wrist-worn tracker every day also during pregnancy and postpartum are needed to obtain more data and robust results on health metrics. This way, women will help each other to understand their bodies better and improve their health.

The overall message is clear: with the right tools and guidance, pregnant women can take control of their health and well-being during pregnancy. Engaging in regular moderate exercise not only enhances the benefits of exercise during pregnancy but also is likely to reduce the hormonal effects on the decline in cardiac coherence during this critical period. By increasing physical activity during pregnancy, women can achieve higher cardiac coherence.

Additionally, following safe aerobic exercises for pregnant women and adhering to guidelines for exercising during pregnancy can significantly promote maternal well-being. Understanding how regular workouts benefit pregnancy health and implementing a balanced diet are essential for preventing gestational hypertension and gestational diabetes. Ultimately, making safe lifestyle changes and recognizing the effects of maternal lifestyle on both mothers and babies’ health leads to better pregnancy outcomes.