Antenatal patterns of uterine activity in low-risk women: a longitudinal study

Alvarez waves in pregnancy: a comprehensive review

Alvarez waves are local rhythmic contractions of the myometrium with high frequency and low intensity. They can be detected using internal or external tocography and electrohysterography. Some researchers correlate these small contractions with the initiation of labor, since they have been described as a pattern representing the uterine response to prostaglandin production. Other authors either do not validate a causality relation between Alvarez waves and labor or suggest that they have low predictive value for preterm labor. Alvarez waves' research has become a multidisciplinary subject with inputs ranging from medical science, biomedical engineering, and related areas. A comprehensive review is herein conducted to summarize the state of the art regarding Alvarez waves and their role in the initiation of labor, namely in preterm birth. The results show that a large number of studies have analyzed and characterized Alvarez waves without necessarily digging into their relationship with labor. Publications were categorized in three groups: (A) reports about morphology and characterization of Alvarez waves; (B) publications reporting a positive causality relation between Alvarez waves and labor; and (C) publications reporting an absence of causality regarding the previous hypothesis. Studies in group B outnumbered those in group C. A critical analysis is presented.

Characterization of Uterine Motion in Early Gestation Using MRI-Based Motion Tracking

Magnetic resonance imaging (MRI) is a promising non-invasive imaging technique that can be safely used to study placental development and function. However, studies of the human placenta performed by MRI are limited by uterine motion and motion in the uterus during MRI remains one of the major limiting factors. Here, we aimed to investigate the characterization of uterine activity during MRI in the second trimester of pregnancy using MRI-based motion tracking. In total, 46 pregnant women were scanned twice (first scan between 14 and 18 weeks and second scan between 19 and 24 weeks), and 20 pregnant subjects underwent a single MRI between 14 and 18 weeks GA, resulting in 112 MRI scans. An MRI-based algorithm was used to track uterine motion in the superior-inferior and left-right directions. Uterine contraction and maternal motion cases were separated by the experts, and unpaired Wilcoxon tests were performed within the groups of gestational age (GA), fetal sex, and placental location in terms of the overall intensity measures of the uterine activity. In total, 22.3% of cases had uterine contraction during MRI, which increased from 18.6% at 14–18 weeks to 26.4% at 19–24 weeks GA. The dominant direction of the uterine contraction and maternal motion was the superior to the inferior direction during early gestation.

Pain and uterine contractions during breast feeding in the immediate post-partum period increase with parity

Previous research has shown that post-partum abdominal pain is greater in multiparous than primiparous women (Murray and Holdcroft, 1989). Although breast feeding in the immediate post-partum period induces uterine contractions and abdominal pain, it is unknown how parity influences the contractions. Here, a structured questionnaire that included the McGill Pain Questionnaire (total pain intensity index, TPI) and visual analog scales (VAS) was used to evaluate the intensity, location, referred tenderness (hyperalgesia), descriptor, and temporal characteristics of pain during breast feeding up to three days after uncomplicated vaginal delivery. Three groups of women were studied: primiparous (n=25); low parity (1-2 prior births; n=14); high parity (3-5 prior births; n=11). Uterine contractions during breast feeding were recorded using tocodynamometry in some women from each group (n=17, 6, 7, respectively). For comparison, an identical questionnaire was used to evaluate pains the women remembered experiencing during menstruation in the year immediately preceding the current pregnancy. During breast feeding, nearly all women (96%) reported deep pain primarily at three sites: lower abdomen, low back, and breast, with associated referred hyperalgesia in 62% of them. The intensity of these pains increased significantly with parity (P<0.001), along with an increase in the number of pain sites (P=0.03), mainly in lower abdomen and back, but not breast. Similarly, both the mean duration and number of uterine contractions increased significantly with parity (P<0.001). Furthermore, the mean duration of contractions correlated significantly with the pain scores (P=0.03 [VAS] and P=0.006 [TPI]). In contrast with pain during breast feeding, the intensity of pain during menstruation did not change with parity. These results demonstrate that pain, referred pain, and uterine contractions during breast feeding in the immediate post-partum period increase with parity, suggesting that childbirth can induce central neural changes that increase predisposition for pain during the post-partum period.

The "Christmas Effect" and other biometeorologic influences on childbearing and the health of women

OBJECTIVE

To review the body of literature addressing biometeorologic and chronobiologic effects on conception, pregnancy, parturition, and other health conditions.

DATA SOURCES

Computerized searches of MEDLINE, PUBMED, CINAHL, and the World Wide Web.

STUDY SELECTION

Studies, including international research, dating from 1938 to 2001.

DATA EXTRACTION

Data were extracted and information organized under the following categories: influence of leisure time and seasonality on the rate of conception and birth, the relationship of meteorologic changes and lunar cycles to childbearing, the "Christmas Effect" and its impact on other health outcomes, and nursing implications.

DATA SYNTHESIS

Research from the disciplines of biometeorology and chronobiology indicates that there are patterns in the occurrence of conception, pregnancy, and onset of labor that vary in timing and amplitude in different populations and geographic regions. Consideration of these factors should be included in the analysis of birth data when planning and providing maternity care. The Christmas Effect is one of the most predominant seasonal patterns that can be seen in birth data throughout the world.

CONCLUSIONS

Biometeorologic and other cyclic phenomena are underused in the United States in planning and providing maternity care. These phenomena warrant consideration when planning holistic health care.