Tamada H, Ichikawa S
Endocrinol Jpn. 1980 Apr;27(2):163-7. doi: 10.1507/endocrj1954.27.163.
In pregnant rats ovariectomized on Day 14 of pregnancy (sperm present=Day 1), the daily injection of 4 mg progesterone maintained normal pregnancy up to Day 17, but injured fetuses bearing hematomata on their extremities appeared very frequently thereafter, in spite of successive injections of progesterone. The addition of 0.2 microgram estradiol-17 beta to the daily dose of progesterone for two successive days between Days 15 and 18 of pregnancy prevented the occurrence of fetal injuries. Estradiol-17 beta was found to be more effective in preventing fetal damage than estrone or estriol. The results suggest that while progesterone is essential for the maintenance of pregnancy, estrogen is also necessary at the time when the conceptus elongates and becomes cylindrical.
在妊娠第14天（受精日为第1天）进行卵巢切除的怀孕大鼠中，每天注射4毫克孕酮可使妊娠维持至第17天正常，但此后尽管连续注射孕酮，四肢带有血肿的受伤胎儿却频繁出现。在妊娠第15天至18天之间连续两天，在每日孕酮剂量中添加0.2微克雌二醇-17β可防止胎儿受伤。发现雌二醇-17β在预防胎儿损伤方面比雌酮或雌三醇更有效。结果表明，虽然孕酮对于维持妊娠至关重要，但在孕体伸长并变成圆柱形时，雌激素也是必需的。
