I'm not sure if it's because there's less to do in winter, people are hibernating, and young couples have more energy, so many children are born around August or September.
Here, August and September refer to the lunar calendar.
Just two days after Niu Xiuying gave birth, Damao from the same production team came to see Feng Qingxue, saying that his wife is about to give birth. By the time Qingxue got to their house, Sanmao, who lived two houses away from Damao, also came over to tell her his wife was in labor.
Just like that, two sisters-in-law went into labor on the same day without a warning.