Related Experiment Video
Updated: Jul 22, 2026
06:49
Methods for Studying Uterine Contributions to Pregnancy Establishment in an Ovariectomized Mouse Model
Published on: April 7, 2023
Pregnancy sickness as an adaptation to concealed ovulation
1Department of Psychology, University of California, San Diego, La Jolla 92093-0109.
Rivista Di Biologia
|January 1, 1994
Summary
Pregnancy sickness may have evolved to reduce sexual activity during early pregnancy, not to expel toxins. This helps prevent uterine cramping that could lead to spontaneous abortion.
Area of Science:
- Evolutionary biology
- Reproductive health
- Human physiology
Background:
- The prevailing hypothesis suggests pregnancy sickness evolved to protect against dietary toxins.
- Previous research indicates a reduction in sexual intercourse frequency during the first trimester of pregnancy.
Purpose of the Study:
- To critically review the toxin-expulsion hypothesis for pregnancy sickness.
- To propose an alternative evolutionary explanation for pregnancy sickness and mastalgia.
Main Methods:
- Critical review of existing literature and hypotheses.
- Comparative analysis of uterine activity during early pregnancy and sexual activity.
Main Results:
- The toxin-expulsion hypothesis for pregnancy sickness is critically evaluated.
- An alternative hypothesis is proposed: pregnancy sickness and mastalgia evolved to decrease coital frequency in early pregnancy.
- Sexual intercourse can induce uterine cramping, potentially increasing the risk of spontaneous abortion in the first trimester.
Conclusions:
- Pregnancy sickness and mastalgia may be adaptations to reduce sexual intercourse frequency during early pregnancy.
- This reduction in intercourse frequency could mitigate the risk of uterine cramping and subsequent spontaneous abortion.
More Related Videos
Related Concept Videos
02:07Oogenesis
In human women, oogenesis produces one mature egg cell or ovum for every precursor cell that enters meiosis. This process differs in two unique ways from the equivalent procedure of spermatogenesis in males. First, meiotic divisions during oogenesis are asymmetric, meaning that a large oocyte (containing most of the cytoplasm) and minor polar body are produced as a result of meiosis I, and again following meiosis II. Since only oocytes will go on to form embryos if fertilized, this unequal...
01:22Hormonal Regulation of the Menstrual Cycle
The ovarian cycle regulates endometrial changes throughout a single menstrual cycle via the coordinated action of gonadotrophin-releasing hormone (GnRH) and gonadotrophins.
At puberty, GnRH begins a pulsatile release pattern, which triggers the anterior pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The frequency and amplitude of GnRH pulses vary across the menstrual cycle, with faster pulses favoring LH release and slower pulses favoring FSH release.
At puberty, GnRH begins a pulsatile release pattern, which triggers the anterior pituitary gland to secrete follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The frequency and amplitude of GnRH pulses vary across the menstrual cycle, with faster pulses favoring LH release and slower pulses favoring FSH release.
01:27Ovarian Cycle
The menstrual cycle includes a critical component known as the ovarian cycle, which undergoes two main phases each month—the follicular phase and the luteal phase. The follicular phase is variable and averaging around 14 days. Ovulation, triggered by a surge in luteinizing hormone (LH), marks the transition between the two phases. The second phase, the luteal phase, is relatively consistent, lasting approximately 14 days, and is marked by the activity of the corpus luteum. While a cycle length...
01:22Oogenesis
Oogenesis, the process of developing egg cells (female gametes), occurs within the ovaries and is fundamental to female fertility. This sequence begins during fetal development when diploid oogonia in the developing ovaries undergo mitotic divisions to produce primary oocytes. By birth, these primary oocytes enter prophase I of meiosis but become arrested in this stage, remaining suspended until puberty.
Each primary oocyte is surrounded by a layer of pre-granulosa cells, forming what is known...
Each primary oocyte is surrounded by a layer of pre-granulosa cells, forming what is known...
01:19Secretory Phase
The secretory phase of the menstrual cycle, spanning from day 14 to 28 in a typical 28-day cycle, is a period of significant physiological changes in the female reproductive system. This phase commences immediately after ovulation and is characterized by the preparation of the endometrium for potential embryo implantation.
Following ovulation, the corpus luteum, a temporary endocrine structure, produces progesterone and estrogens. These hormones stimulate the growth and coiling of endometrial...
Following ovulation, the corpus luteum, a temporary endocrine structure, produces progesterone and estrogens. These hormones stimulate the growth and coiling of endometrial...
01:22Birth Control Methods
Vasectomy is a surgical form of male sterilization that involves severing and sealing the vasa deferentia, preventing sperm from mixing with semen during ejaculation. Because a vasectomy does not impact the testes' ability to produce testosterone, hormone levels, libido, and sexual function generally remain unchanged. While vasectomy is highly effective in preventing pregnancy, with a success rate near 99.85%, rare cases of recanalization (spontaneous reconnection) can occur. Although vasectomy...