What to Pray for When You’re Pregnant

How did the rabbis of the Talmud know details of pregnancy 1500 years before science did?

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There are no atheists in foxholes, and every expectant parent prays for the wellbeing of the life growing inside the mother. So first, I assume you’re here because you or someone you know is pregnant. Good luck and bless you.

The Jews have ancient wisdom for what to pray for when you’re pregnant.  In fact, the Talmud prescribes different prayers for different stages in the pregnancy that incredibly correspond to biological facts that science wouldn’t know about for fifteen hundred years.

Here’s the schedule of prayers they prescribe (in Berachot 60a):

Within the first three days you should pray that the seed should not go bad.

From the third to the fortieth day, pray for the gender of the child.

From the fortieth day to three months, pray that it doesn’t suffer from serious deformities.

From three to six months, pray that the fetus remains viable.

From six months to nine months pray for a safe delivery.

Collectively, the rabbis of the Talmud show remarkable acuity about biology, chemistry, astronomy, botany, and the physics of their day. Some of their knowledge came, of course, from surrounding cultures: the Greeks and Romans performed regular autopsies on fetuses, for instance. But it is farfetched to speculate that they knew the subtleties and timing of development of the fetus some of which weren’t established until the twentieth century.

How did they know more than the Greeks and Romans? Where did the knowledge come from? 

First three days after conception: “Please don’t let my seed go bad or spoil”

The Talmud’s first prayer, that the seed should not spoil, is to be said within three days after the moment of conception.

But let’s back up. This begs the question of how a woman or her husband would even know the day of conception. There were obviously no pregnancy tests then like there are today (which measure a specific hormone, human chorionic gonadotropin (HCG) only released when a fertilized egg attaches to the lining of the mother’s uterus; in other words, when pregnancy begins). Those weren’t developed until a couple of decades ago.

Maybe this prayer was to be said after every act of intercourse, just in case. Not a bad idea, really.

Praying during the first three days after conception has the same mystery. Short of intuition (certainly possible) or a modern pregnancy test, most women don’t know they are pregnant until they miss their first period, which on average is many days or four weeks after the actual moment.

Before conception, a woman’s body produces a cervical mucous that creates a protective environment for sperm. If a sperm swims beyond the cervix and overcomes the many hurdles in making it to the uterus, they live about three days! If it succeeds, it penetrates the mucosal defense and attaches to the wall of the uterus.

So praying to make the sperm viable in the first three days after intercourse shows inexplicable insight into the phenomenon. The sages couldn’t possibly learn this from an outside source. Spermatoza weren’t even discovered until 1677 when van Leeuwenhoek saw them through his microscope, and the sages would have had no way to confirm that sperm remains viable for that long in the uterus nor that a female egg could be fertilized by it.

From 3 to 40 days after conception: “Please make the baby [a specific gender]”

Of course in the Tamudic era (200-500 CE) and in virtually every era and culture into the twentieth century, this prayer is explicitly for a male. So an allegation of sexism might be strictly accurate, but anachronistic, a little like condemning Shakespeare because he wasn’t Marxist. But the perfect timing of the prayer is still mystifying.

During the first few weeks after fertilization, the embryo is in a so-called “indifferent phase” of determining its sex. It has both male (Wolffian ducts) and female (Mullerian duct) organs, regardless of whether it is ultimately going to be a boy or a girl. In other words, the embryo is literally neither male nor female but both, potentially. At this point, it is no larger than a pea. At around the sixth week  after conception, a tiny (less than 1 millimeter) genital bump called the “genital tube” appears. Until the ninth week, the reproductive apparatus – internal tubes, organs, etc. – is identical in all babies in the womb whether they will eventually become male or female.

That is why even though the intrinsic XY (male) or XX (female) genetic identity of the embryo is determined at fertilization, when something goes wrong with morphology – the expression of the genes into physical characteristics – a fetus with both male and female or ambiguous organs, an androgyne (from the Greek for “man- woman”) might develop.

This precision about the exact point at which gender is “expressed” and its genetic mechanism has only been established in the last century.  In other words, even if the rabbis studied or received information about dissected fetuses, they would have to see and understand the function of a 1mm bump (of which there is no documentation).

So it’s remarkable that the rabbis prescribe a prayer for the sex of the baby in this specific period. It begs another extraordinary question: How did the rabbis know the determination of gender – male or female – could even be answered one way or another, let alone in this specific time period? Even posing the question itself is mystifying. Why do the rabbis assume gender could even be determined after conception and not determined at conception as was generally believed by all other cultures of the time? Aristotle, whose scientific speculations ruled Western scientific knowledge through the medieval period, believed the gender of the fetus was determined by the heat of sperm at conception

In short, the prayer for the gender of the child in the Talmud transcends rational explanation. It seems the sages of the Talmud were in touch with a stream of knowledge that seems to come from beyond empirical observation of the material world.

4. Forty days to 3 months: “Please don’t let the fetus become deformed!”

This prayer is designed to prevent gross physiological abnormalities in the development of the baby. The study of the progress and causes of congenital anomalies, a science that arose in the last two centuries, is called “teratology.”

About 30 days into fetal development, the embryo develops pharangyeal (throat) arches that look like gills. It’s hard to say the fetus looks like a human being until about the sixteenth week (about 110 days) or later. About four months into development, when the fetus is about five inches long, cartilage hardens into bone. Until then, any aborted fetus would look something more like a small fish. The term the rabbis use for deformity is “sandal,” an Aramaic word ‘sandal‘ for a flat ocean fish that literally looked like a sandal, perhaps a flounder (which is so flat it has both eyes on the side of its body facing up).

However, the Talmud here seems to have knowledge of a popular scientific theory of the nineteenth century that at different stages of its development, a baby in the womb superficially looks like animals from different stages of evolution, from unicellular organisms through tadpoles and fish, to more complex species, to mammals and primates, and finally humans. Ernst Haeckel summarized it with a famous phrase “ontogeny recapitulates phylogeny“: the growth of a single organism in utero mimics the procession of the phyla of species up the evolutionary chain.

Of all the prayers, this is the one that more likely is explained by accumulated observation over generations.

5. From 3 to 6 months: “Please don’t let the fetus become nonviable” (a miscarriage)

This is an obvious anxiety that the mother or father would pray to avoid. Yet most miscarriages occur before the 8-12th week of pregnancy; that is, before three months. So why do the sages prescribe it for after the most dangerous period is over?

One answer may be that by the beginning of the second trimester the mother is keenly aware of the vital being growing inside her. Furthermore, even though most miscarriages occur in the first trimester, the jeopardy to the mother’s health through miscarriage now starts to increase dramatically! In Jewish law, until the baby emerges, the mother’s health takes precedence over concerns about the life growing inside her.

6. Six months until end of term: “Please show mercy by letting the baby emerge!”

By now, everyone is getting eager for the pregnancy to come to term. You can’t help but smile at this one. The prayer has a minor flavor saying, “Please let’s get it over with!” But it is also true that chances of the viability of the fetus greatly increase. The viability of a six-month old fetus reaches 50% exactly at the 23.5th week, or in the six month!

A River of Secret Knowledge

So what was the rabbis’ source of their prescience if not direct observation or inherited Roman and Greek scientific wisdom?

Jewish tradition says that there is a river of secret knowledge that flows from the time Moses was on Sinai three thousand three hundred years ago and got the two tablets inscribed by the finger of God. Along with the written Torah, God also communicated compendium of wisdom passed down from Moses through word of mouth from generation to generation, the Torah she ba’alpeh. This Oral Law contains knowledge that is still unfolding and still being confirmed by science. According to this traditional belief, since God created the universe and both the Written and Oral Torahs are His cookbook for Creation, all knowledge is contained within them.  The rabbis’ extensive foreknowledge of later science seems to confirm this belief that they had access to secret wisdom.

The transcendent source of life

Finally, we need to acknowledge how fitting it is for us to pray for a successful pregnancy and to thereby acknowledge its transcendent and sacred source. Science has not succeeded in creating any new life from non-living matter. This is quite surprising, given both the advanced state of our knowledge of biology and the number of times biology has boasted we are close to creating life. Yet, the Frankenstein fantasy of forming new life from inert materials – both a wish and a nightmare which has haunted us since at least 1818 – has never materialized, despite our incredible advances in genetics, biochemistry, and biophysics.

I personally happen to believe we never will succeed in making life except the old fashioned way. And why should we try when the one sure way is so much fun.

Of course this is an assertion of blind faith, and one day I may be proven wrong. But if you believe in a spiritual dimension to the universe, and more specifically in the God that Abraham brought to the world, then creating life is a talent reserved for Him, and creating a new human being can only be done in partnership between humans and God.

In the interim, as we’re suspended between the scientific hope to create life and the mystical faith that only God can do it, it seems to me that praying for the success of bringing a new soul into the world, one of the most fervent requests you can imagine, is a pretty fine way for the mother- and father-to-be to spend the nine months wait.


I’d like to note Leah Poltorak’s piece, “On the Embryological Foresight of the Talmud,” B’Or Ha’Torah 19 (5770/2009) which treats the same prescient moment in the Talmud. I only came across her article in 2022. She makes substantially the same point: “We can only marvel at the foresight of the Talmud Sages, who, almost a millennium and a half before the Age of Science, not only understood that both parents contribute to the biological development of their child, but were able to accurately determine the time line of embryonic gender development.”