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Cardiovascular Function Before, During, and After the First and Subsequent Pregnancies

https://doi.org/10.1016/S0002-9149(97)00738-8Get rights and content

Abstract

This study was designed to test the hypothesis that the vascular remodeling of pregnancy begins early, persists for at least 1 year after delivery, and is accentuated by a second pregnancy. Serial estimates of heart rate, arterial pressure, left ventricular volumes, cardiac output, and calculated peripheral resistance were obtained before pregnancy, every 8 weeks during pregnancy, and 12, 24, and 52 weeks postpartum in 15 nulliparous and 15 parous women using electrocardiography, automated manometry, and M-mode ultrasound. During pregnancy, body weight increased 14.5 ± 1.8 kg and returned to prepregnancy values 1 year postpartum. Heart rate peaked at term 15 ± 1 beat/min above prepregnancy levels (57 ± 1 beat/min). Mean arterial pressure reached its nadir (−6 ± 1 mm Hg) at 16 weeks, returning to baseline at term. The increases in left ventricular volumes and cardiac output (2.2 ± 0.2 L/min) peaked at 24 weeks as did the 500 ± 29 dynes·cm·s−5 decrease in peripheral resistance, and their magnitude was significantly greater in the parous women. Postpartum they gradually returned toward baseline but remained significantly different from prepregnancy values in both groups at 1 year. We conclude that cardiovascular adaptations to the initial pregnancy begin early, persist postpartum, and appear to be enhanced by a subsequent pregnancy. We speculate that persistence of these changes may lower cardiovascular risk in later life.

Section snippets

Study Group:

Thirty, healthy, physically active, nonsmoking women were recruited before pregnancy and studied serially before, during, and for 1 year after a clinically normal, singleton pregnancy. Fifteen were nulliparous and 15 were parous (1 or 2 previous pregnancies) at the time of enrollment. All delivered at term, breast fed for 3 to 9 months, and used barrier forms of contraception. The protocol was approved by the institutional review committees and all subjects gave informed consent at the time of

Subject Characteristics:

The subjects all were in good health, and, on the basis of education (18 ± 1 year) and income (upper 2 quartiles for state and county of residence), were classified as coming from the middle and upper socioeconomic class. Most (26 of 30) exercised regularly before, during, and after their pregnancy. They were 32 ± 1 years of age, weighed 61.0 ± 1.8 kg before pregnancy, and returned to that weight by 1 year after delivery (61.6 ± 1.8 kg). Their prepregnancy percent body fat, estimated from 5

Discussion

To the best of our knowledge, this study is the first that has prospectively assessed the serial changes in central cardiovascular function in healthy women before, during, and for a protracted period of time after pregnancy. The data confirm earlier findings indicating that the cardiovascular changes of pregnancy begin early and are largely completed in the first half of pregnancy.1, 5, 6, 7, 11 Second, the consistent differences seen in the magnitude of the absolute changes in the parous

Acknowledgements

Acknowledgment:

We wish to thank Karen H. Risk, Sarah Appleby-Wineberg, Mary Kortan, and Beth Lopez for there expert assistance in conducting these studies.

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    This study was supported by National Institutes of Health Grants HD11089, HD21268, and RR00080, Bethesda, Maryland; and funds from MetroHealth Medical Center, Cleveland Ohio, and the Alexander von Humboldt Foundation, Bonn, Germany.

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